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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 294 (1992), S. 466-478 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 317 (1993), S. 474-484 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2022-05-25
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Jacox, M. G., Alexander, M. A., Siedlecki, S., Chen, K., Kwon, Y., Brodie, S., Ortiz, I., Tommasi, D., Widlansky, M. J., Barrie, D., Capotondi, A., Cheng, W., Di Lorenzo, E., Edwards, C., Fiechter, J., Fratantoni, P., Hazen, E. L., Hermann, A. J., Kumar, A., Miller, A. J., Pirhalla, D., Buil, M. P., Ray, S., Sheridan, S. C., Subramanian, A., Thompson, P., Thorne, L., Annamalai, H., Aydin, K., Bograd, S. J., Griffis, R. B., Kearney, K., Kim, H., Mariotti, A., Merrifield, M., & Rykaczewski, R. Seasonal-to-interannual prediction of North American coastal marine ecosystems: forecast methods, mechanisms of predictability, and priority developments. Progress in Oceanography, 183, (2020): 102307, doi:10.1016/j.pocean.2020.102307.
    Description: Marine ecosystem forecasting is an area of active research and rapid development. Promise has been shown for skillful prediction of physical, biogeochemical, and ecological variables on a range of timescales, suggesting potential for forecasts to aid in the management of living marine resources and coastal communities. However, the mechanisms underlying forecast skill in marine ecosystems are often poorly understood, and many forecasts, especially for biological variables, rely on empirical statistical relationships developed from historical observations. Here, we review statistical and dynamical marine ecosystem forecasting methods and highlight examples of their application along U.S. coastlines for seasonal-to-interannual (1–24 month) prediction of properties ranging from coastal sea level to marine top predator distributions. We then describe known mechanisms governing marine ecosystem predictability and how they have been used in forecasts to date. These mechanisms include physical atmospheric and oceanic processes, biogeochemical and ecological responses to physical forcing, and intrinsic characteristics of species themselves. In reviewing the state of the knowledge on forecasting techniques and mechanisms underlying marine ecosystem predictability, we aim to facilitate forecast development and uptake by (i) identifying methods and processes that can be exploited for development of skillful regional forecasts, (ii) informing priorities for forecast development and verification, and (iii) improving understanding of conditional forecast skill (i.e., a priori knowledge of whether a forecast is likely to be skillful). While we focus primarily on coastal marine ecosystems surrounding North America (and the U.S. in particular), we detail forecast methods, physical and biological mechanisms, and priority developments that are globally relevant.
    Description: This study was supported by the NOAA Climate Program Office’s Modeling, Analysis, Predictions, and Projections (MAPP) program through grants NA17OAR4310108, NA17OAR4310112, NA17OAR4310111, NA17OAR4310110, NA17OAR4310109, NA17OAR4310104, NA17OAR4310106, and NA17OAR4310113. This paper is a product of the NOAA/MAPP Marine Prediction Task Force.
    Keywords: Prediction ; Predictability ; Forecast ; Ecological forecast ; Mechanism ; Seasonal ; Interannual ; Large marine ecosystem
    Repository Name: Woods Hole Open Access Server
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  • 4
    Publication Date: 2022-02-16
    Description: On September 6, 2017, the solar active region AR 2673 emitted two solar flares: the first at 08:57 UT (X2.2) and the second at 11:53 UT (X9.3); both were powerful enough to black-out high and low frequency radio waves (where UT is universal time). The X9.3 was the strongest solar flare event in the past decade. In this study, we took the advantage of these two extreme flare events to investigate corresponding effects on the ionosphere using multi-instrument observations from magnetometers, Global Positioning System – Total Electron content (GPS-TEC) receivers, ionosondes and Swarm satellites over a large geographical extent covering South American, African and European sectors. During the X2.2 flare, European and African sectors were sunlit and during X9.3 European, African, and South American sectors were sunlit and exposed to the solar flare radiation. During the X2.2 flare, there was an ionosonde blackout for a duration of about 45 min, while during the X9.3 flare this blackout lasted for 1 h and 30 min. The blackout are seen over a large global extent which demonstrates the severity of solar flare events in disrupting the radio communication. The horizontal component of Earth’s geomagnetic field has shown ripples and enhancements during these flare events. The ionospheric Vertical Total Electron Content (VTEC) showed a positive phase along with an intensification of the Equatorial Ionization Anomaly (EIA) over the South American and African sectors. The dynamical and physical processes associated with the TEC and EIA variabilities due to solar flare are discussed.
    Description: Published
    Description: 1775-1791
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
    Publication Date: 2022-01-07
    Description: Palaeoenvironmental reconstructions with temporal coverages extending beyond Marine Isotope Stage (MIS) three are scarce within the data sparse region of Chukotka, Far East Russia. The objective of this paper is to infer palaeoenvironmental variability from a 10.76 m long, OSL- and 14C- dated sediment core from Lake Ilirney, Chukotka (67°21′N, 168°19′E). We analysed high-resolution sediment-geochemistry (XRF), sedimentology (TC, TN, TOC, grain-size), mineralogy (XRD) and preliminary micropalaeontological data (diatoms and pollen) from the core as well as acoustic sub-bottom profiling data from the lake basin. Our results affirm the application of XRF-based sediment-geochemical proxies as effective tracers of palaeoenvironmental variability within arctic lake systems. Our study reveals that a lake formed during MIS3 from 51.8 (±4.1) ka BP, following extensive MIS4 glaciation. Catchment palaeoenvironmental conditions during this time remained harsh associated with the continued presence of a catchment glacier until 36.2 (±2.6) ka BP. Partial amelioration reflected by increased diatom, catchment vegetation and lake organic productivity and clastic sediment input from mixed sources from 36.2 (±2.6) ka BP resulted in a lake high-stand ∼15 m above present and is interpreted as evidence of a more productive palaeoenvironment coincident with the MIS3 interstadial optimum. A transitional period of deteriorating palaeoenvironmental conditions occurred ∼30–27.9 ka BP and was superseded by periglacial-glacial conditions from 27.9 (±0.8) ka BP, during the last glacial maximum. Deglaciation as marked by sediment-geochemical proxies commenced at 20.2 (±0.8) ka BP. Our findings are compared with lacustrine, Yedoma and river-bluff records from across Beringia and potentially yield limited support for a marked Younger Dryas cooling in the study area.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
    Publication Date: 2022-06-20
    Description: Between 2003-2016, the Greenland ice sheet (GrIS) was one of the largest contributors to sea level rise, as it lost about 255 Gt of ice per year. This mass loss slowed in 2017 and 2018 to about 100 Gt yr−1. Here we examine further changes in rate of GrIS mass loss, by analyzing data from the GRACE-FO (Gravity Recovery and Climate Experiment – Follow On) satellite mission, launched in May 2018. Using simulations with regional climate models we show that the mass losses observed in 2017 and 2018 by the GRACE and GRACE-FO missions are lower than in any other two year period between 2003 and 2019, the combined period of the two missions. We find that this reduced ice loss results from two anomalous cold summers in western Greenland, compounded by snow-rich autumn and winter conditions in the east. For 2019, GRACE-FO reveals a return to high melt rates leading to a mass loss of 223 ± 12 Gt month−1 during the month of July alone, and a record annual mass loss of 532 ± 58 Gt yr−1.
    Repository Name: EPIC Alfred Wegener Institut
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  • 7
    Publication Date: 2022-06-10
    Description: In fold and thrust belts developing at convergent margins, the migration of the advancing wedge is accompanied by bulging of the downgoing plate, followed by the development of a foredeep basin filled by a thick succession of syn-orogenic sediments. The transition from forebulge to foredeep marks a key moment in the evolution of the orogenic system. In deep water environments, the record of this transition is typically complete and progressive. Conversely, in the shallow-water/continental environment of many collisional systems, the uplift of the forebulge area can imply emersion and erosion, obliterating the stratigraphic record of key steps of the evolution of the orogenic system. The southern Apennines constitute one of these collisional fold and thrust belts where the development of the forebulge has implied emersion and erosion, with the development of a Miocene forebulge erosional unconformity, accompanied by extensional deformation associated with the bending of the lithosphere during the forebulge stage. In this paper, we use strontium isotope stratigraphy to constrain with unprecedented time-resolution the age of the forebulge unconformity in areas presently incorporated in the northern sector of the southern Apennines fold and thrust belt. Integration of our results and those of previous studies indicates, at the regional scale, a younging toward the foreland of the forebulge unconformity across the belt. Our highresolution ages also reveal a diachronous onset of the flexural subsidence over short distances, associated with the occurrence of horst and graben structures, possibly resulting from inherited paleotopography along with forebulge extension. This work highlights how high-resolution dating is critical to unravel the evolution of foreland basin systems at different scales.
    Description: Published
    Description: 105634
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: 2TR. Ricostruzione e modellazione della struttura crostale
    Description: 2IT. Laboratori analitici e sperimentali
    Description: JCR Journal
    Keywords: Foreland basin system ; Forebulge unconformity ; Strontium isotope stratigraphy ; Forebulge extension ; Miocene ; Southern Apennines (Italy)
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Du, J., Park, K., Yu, X., Zhang, Y. J., & Ye, F. Massive pollutants released to Galveston Bay during Hurricane Harvey: Understanding their retention and pathway using Lagrangian numerical simulations. Science of the Total Environment, 704, (2019): 135364, doi: 10.1016/j.scitotenv.2019.135364.
    Description: Increasing frequency of extreme precipitation events under the future warming climate makes the storm-related pollutant release more and more threatening to coastal ecosystems. Hurricane Harvey, a 1000-year extreme precipitation event, caused massive pollutant release from the Houston metropolitan area to the adjacent Galveston Bay. 0.57 × 106 tons of raw sewage and 22,000 barrels of oil, refined fuels and chemicals were reportly released during Harvey, which would likely deteriorate the water quality and damage the coastal ecosystem. Using a Lagrangian particle-tracking method coupled with a validated 3D hydrodynamic model, we examined the retention, pathway, and fate of the released pollutants. A new timescale, local exposure time (LET), is introduced to quantitatively evaluate the spatially varying susceptibility inside the bay and over the shelf, with a larger LET indicating the region is more susceptible to the released pollutants. We found LET inside the bay is at least one order of magnitude larger for post-storm release than storm release due to a quick recovery in the system's flushing. More than 90% of pollutants released during the storm exited the bay within two days, while those released after the storm could stay inside the bay for up to three months. This implies that post-storm release is potentially more damaging to water quality and ecosystem health. Our results suggest that not only the amount of total pollutant load but also the release timing should be considered when assessing a storm's environmental and ecological influence, because there could be large amounts of pollutants steadily and slowly discharged after storm through groundwater, sewage systems, and reservoirs.
    Description: We like to acknowledge the Texas Coastal Management Program, the Texas General Land Office and NOAA for partial funding of this project through CMP Contract #19-040-000-B074. This work was performed using computing facilities at the College of William and Mary, which were provided by contributions from the National Science Foundation, the Commonwealth of Virginia Equipment Trust Fund and the Office of Naval Research.
    Keywords: Storm discharge ; Retention ; Local exposure time ; Particle tracking ; SCHISM
    Repository Name: Woods Hole Open Access Server
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  • 9
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Mundl-Petermeier, A., Walker, R. J., Jackson, M. G., Blichert-Toft, J., Kurz, M. D., & Halldorsson, S. A. Temporal evolution of primordial tungsten-182 and he-3/He-4 signatures in the Iceland mantle plume. Chemical Geology, 525, (2019): 245-259. doi: 10.1016/j.chemgeo.2019.07.026.
    Description: Studies of short-lived radiogenic isotope systems and noble gas isotopic compositions of plume-derived rocks suggest the existence of primordial domains in Earth's present-day mantle. Tungsten-182 anomalies together with high 3He/4He in Phanerozoic rocks from large igneous provinces and ocean island basalts demonstrate the preservation of early-formed (within the first 60 Ma of solar system history) mantle domains tapped by modern mantle plumes. It has proven difficult to link the evidence for primordial domains with geochemical evidence for more recent processes, such as recycling. The Greenland-Iceland plume system, starting with eruptions of the Paleocene North Atlantic Igneous Province, is later manifested in the mid-Miocene to modern volcanic products of Iceland. Here, we report Pb isotopic compositions, μ182W (deviations in 182W/184W of a sample from a laboratory reference standard in parts per million), and 3He/4He, as well as highly siderophile element concentrations and Re-Os isotopic systematics of basaltic samples erupted at different times during the ~60 Ma history of the Greenland-Iceland plume. Paleocene samples from Greenland, representing the early stage of the mantle plume, are characterized by variable 3He/4He ranging from 7 to 48 R/RA (measured 3He/4He normalized to the atmospheric ratio) and an average μ182W of −4.0 ± 3.6 (2SD), within modern upper mantle-like values of 0 ± 4.5. The basalts from Iceland can be divided into two groups based on their Pb isotope compositions. One group, consisting mostly of Miocene basalts, is characterized by 206Pb/204Pb ranging from ~18.4 to 18.5, 3He/4He ranging from 17.8 to 40.2 R/RA, and μ182W values ranging from +1.7 to −9.1 ± 4.5. The other group, consisting mainly of Pleistocene and Holocene basalts, is characterized by higher 206Pb/204Pb, ranging from ~18.7 to 19.2, 3He/4He ranging from 7.9 to 25.7 R/RA, and μ182W values ranging from −0.6 to −11.7 ± 4.5. Collectively, the Greenland-Iceland suite examined requires mixing between a minimum of three mantle source domains characterized by distinct Pb-He-W isotopic compositions, in order to account for this range of isotopic data. The temporal changes in the isotopic data for these rocks appear to track the dominant contributing plume components as the system evolved. One of the domains is indistinguishable from the ambient upper oceanic mantle and contributed substantial material throughout the time progression. The other two domains are most likely primordial reservoirs that underwent limited de-gassing. Given the negative μ182W values in some rocks, one of these domains likely formed within the first 60 Ma of solar system history and is a major contributor to the youngest basalts. The isotopic characteristics of Greenland-Iceland plume-derived rocks reveal episodic changes in the source component proportions.
    Description: This study was supported by NSF grant EAR-1624587 (to RJW and AMP). AMP acknowledges FWF grant V659-N29. MJ acknowledges NSF grant EAR-1624840, and MK acknowledges OCE-1259218. We would like to thank Lotte M. Larsen and Asger K. Pedersen for providing the West Greenland samples, and Bernard Marty for the samples from East Greenland. We thank Catherine Chauvel for the editorial handling and Rita Parai, Dominique Weis, David Graham and an anonymous reviewer for the helpful and constructive comments on this and an earlier version of the manuscript.
    Keywords: μ182W ; Iceland ; Mantle plume ; 3He/4He ; Primordial reservoir
    Repository Name: Woods Hole Open Access Server
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  • 10
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wheat, C. G., Seewald, J. S., & Takai, K. Fluid transport and reaction processes within a serpentinite mud volcano: South Chamorro Seamount. Geochimica Et Cosmochimica Acta, 269, (2020): 413-428, doi: 10.1016/j.gca.2019.10.037
    Description: Natural fluids with a pH (25 °C) up to 12.3 were collected from a sub-seafloor borehole observatory (Ocean Drilling Program (ODP) Hole 1200C) on South Chamorro Seamount, a serpentinite mud volcano in the Mariana forearc. We used systematic differences in the chemical compositions of pore waters from drilling operations during ODP Leg 195 and borehole fluids collected subsequently from Hole 1200C to define two endmember solutions, one of which was a sulfate-rich fluid with a methane concentration of 50 mM that ascends from the subduction channel and the other was a low-sulfate fluid. The sequence of sample collection and fluid compositions constrain subsurface hydrologic conditions. Deep-sourced, sulfate- and methane-rich, sterile fluids from the subduction channel can reach the seafloor unchanged within the central conduit, whereas other fluid pathways likely intersect the pelagic sediment that underlies the serpentinite mud volcano, providing potentially suitable conditions and inoculum for microbial anaerobic oxidation of methane (AOM). These AOM-affected, low-sulfate fluids also make it to the seafloor where they discharge. The source of the sulfate- and methane-rich fluid in the subduction channel is attributed to abiotic methane production fueled by hydrogen production from serpentinization and carbonate dissolution. This methane production includes a mechanism to raise the pH above values from serpentinization alone. Results from South Chamorro Seamount represent an end member along a transect defined by the distance from the trench. Results from this site are applied to other serpentinite mud volcanoes along this transect to speculate on likely chemical conditions within shallower and cooler portions of the subduction channel.
    Description: The authors thank the entire shipboard parties of cruises NT09-01 and NT09-07 on the R/V Nastushima and the crews and pilots of the ROV HyperDolphin. We also thank Tom Pettigrew for removing the dummy plug and designing the insert for the borehole. This research was supported by the National Science Foundation (OCE-0727120 and 1439564 (CGW) and OCE--0725204 (JS)) and the Japan Agency for Marine-Earth Science and Technology. This is C-DEBI contribution 497.
    Keywords: Serpentinization ; Mud volcano ; Subduction ; Mariana forearc ; Dissolved gases ; Anaerobic methane oxidation
    Repository Name: Woods Hole Open Access Server
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  • 11
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Horowitz, E. J., Cochran, J. K., Bacon, M. P., & Hirschberg, D. J. 210Po and 210Pb distributions during a phytoplankton bloom in the North Atlantic: implications for POC export. Deep-Sea Research Part I: Oceanographic Research Papers, 164, (2020): 103339, doi:10.1016/j.dsr.2020.103339.
    Description: During the North Atlantic Bloom Experiment (NABE) of the Joint Global Ocean Flux Study (JGOFS), water column sampling for particulate and dissolved 210Po and 210Pb was performed four times (26 April and 4, 20, 30 May 1989) during a month-long Lagrangian time-series occupation of the NABE site, as well as one-time samplings at stations during transit to and from the site. There are few prior studies documenting short-term changes in 210Po and 210Pb profiles over the course of a phytoplankton bloom, and we interpret the profiles in terms of the classical “steady-state” (SS) approach used in most studies, as well as by using a non-steady state approach suggested by the temporal evolution of the profiles. Changes in 210Po profiles during a bloom are expectable as this radionuclide is scavenged and exported. During NABE, 210Pb profiles also displayed non-steady state, with significant increases in upper water column inventory occurring midway through the experiment. Export of 210Po from the upper 150 m using the classic “steady-state” model shows increases from 0.5 ± 8.5 dpm m−2 d−1 to 68.2 ± 4.2 dpm m−2 d−1 over the ~one-month occupation. Application of a non-steady state model, including changes in both 210Pb and 210Po profiles, gives higher 210Po export fluxes. Detailed depth profiles of particulate organic carbon (〉0.8 μm) and particulate 210Po (〉0.4 μm) are available from the 20 and 30 May samplings and show maxima in POC/Po at ~37 m. Applying the POC/210Po ratios at 150 m to the “steady state” 210Po fluxes yields POC export from the upper 150 m of 8.2 ± 1.5 mmol C m− 2 d−1 on 20 May and 6.0 ± 1.6 mmol C m−2 d−1 on 30 May. The non-steady state model applied to the interval 20 to 30 May yields POC export of 24.3 mmol C m−2 d−1. The non-steady state (NSS) 210Po-derived POC fluxes are comparable to, but somewhat less than, those estimated previously from 234Th/238U disequilibrium for the same time interval (37.3 and 45.0 mmol m−2 d−1, depending on the POC/Th ratio used). In comparison, POC fluxes measured with a floating sediment trap deployed at 150 m from 20 to 30 May were 11.6 mmol m−2 d−1. These results suggest that non-steady state Po-derived POC fluxes during the NABE agree well with those derived from 234Th/238U disequilibrium and agree with sediment trap fluxes within a factor of ~2. However, unlike the 234Th-POC flux proxy, non-steady stage changes in profiles of 210Pb, the precursor of 210Po, must be considered.
    Description: We are grateful to T. Hammar and A. Fleer (WHOI) for assistance at sea and in the laboratory. This work was supported originally by National Science Foundation (United States) grant OCE-8819544 to JKC and more recently by OCE-1736591. We thank Stephen Thurston (American Museum of Natural History) for graphics assistance Robert Aller, Steven Beaupre, and two anonymous reviewers for helpful comments.
    Keywords: Polonium-210 ; Lead-210 ; 210Po ; 210Pb ; North Atlantic ; Spring bloom ; POC flux
    Repository Name: Woods Hole Open Access Server
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  • 12
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lin, P., Pickart, R. S., Fissel, D., Ross, E., Kasper, J., Bahr, F., Torres, D. J., O'Brien, J., Borg, K., Melling, H., & Wiese, F. K. Circulation in the vicinity of Mackenzie Canyon from a year-long mooring array. Progress in Oceanography, 187, (2020): 102396, doi:10.1016/j.pocean.2020.102396.
    Description: Data from a five-mooring array extending from the inner shelf to the continental slope in the vicinity of Mackenzie Canyon, Beaufort Sea are analyzed to elucidate the components of the boundary current system and their variability. The array, part of the Marine Arctic Ecosystem Study (MARES), was deployed from October 2016 to September 2017. Four distinct currents were identified: an eastward-directed flow adjacent to the coast; a westward-flowing, surface-intensified current centered on the outer-shelf; a bottom-intensified shelfbreak jet flowing to the east; and a recirculation at the base of the continental slope within the canyon. The shelf current transports −0.120.03 Sv in the mean and is primarily wind-driven. The response is modulated by the presence of ice, with little-to-no signal during periods of nearly-immobile ice cover and maximum response when there is partial ice cover. The shelfbreak jet transports 0.030.02 Sv in the mean, compared to 0.080.02 Sv measured upstream in the Alaskan Beaufort Sea over the same time period. The loss of transport is consistent with a previous energetics analysis and the lack of Pacific-origin summer water downstream. The recirculation in the canyon appears to be the result of local dynamics whereby a portion of the westward-flowing southern limb of the Beaufort Gyre is diverted up the canyon across isobaths. This interpretation is supported by the fact that the low-frequency variability of the recirculation is correlated with the wind-stress curl in the Canada Basin, which drives the Beaufort gyre.
    Description: The authors are indebted to Fisheries and Oceans Canada for building the logistics for MARES into the at-sea missions of the Integrated Beaufort Observatory. We are grateful to the captain and crew of the CCGS Sir Wilfred Laurier for ably deploying and recovering the MARES array. Marshall Swartz assisted with the cruise preparation logistics. We thank the two anonymous reviewers for their input which helped improve the paper. This project was funded by the US Bureau of Ocean Energy Management (BOEM), on behalf of the National Ocean Partnership Program. The Canadian contribution was supported by the Environmental Studies Research Fund (ESRF Project 2014-02N). MARES publication 003.
    Keywords: Canadian Beaufort Sea ; Mackenzie Canyon ; Boundary currents ; Canyon circulation ; Ice-ocean interaction
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  • 13
    Publication Date: 2022-10-27
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hirst, W. G., Biswas, A., Mahalingan, K. K., & Reber, S. Differences in intrinsic tubulin dynamic properties contribute to spindle length control in Xenopus species. Current Biology, 30(11), (2020): 2184-2190.e5, doi: 10.1016/j.cub.2020.03.067.
    Description: The function of cellular organelles relates not only to their molecular composition but also to their size. However, how the size of dynamic mesoscale structures is established and maintained remains poorly understood [1, 2, 3]. Mitotic spindle length, for example, varies several-fold among cell types and among different organisms [4]. Although most studies on spindle size control focus on changes in proteins that regulate microtubule dynamics [5, 6, 7, 8], the contribution of the spindle’s main building block, the αβ-tubulin heterodimer, has yet to be studied. Apart from microtubule-associated proteins and motors, two factors have been shown to contribute to the heterogeneity of microtubule dynamics: tubulin isoform composition [9, 10] and post-translational modifications [11]. In the past, studying the contribution of tubulin and microtubules to spindle assembly has been limited by the fact that physiologically relevant tubulins were not available. Here, we show that tubulins purified from two closely related frogs, Xenopus laevis and Xenopus tropicalis, have surprisingly different microtubule dynamics in vitro. X. laevis microtubules combine very fast growth and infrequent catastrophes. In contrast, X. tropicalis microtubules grow slower and catastrophe more frequently. We show that spindle length and microtubule mass can be controlled by titrating the ratios of the tubulins from the two frog species. Furthermore, we combine our in vitro reconstitution assay and egg extract experiments with computational modeling to show that differences in intrinsic properties of different tubulins contribute to the control of microtubule mass and therefore set steady-state spindle length.
    Description: This article was prompted by our stay at the Marine Biological Laboratory (MBL), Woods Hole, MA in the summer of 2016 funded by the Princeton-Humboldt Strategic Partnership Grant together with the lab of Sabine Petry (Princeton University). We thank Jeff Woodruff (UT Southwestern), David Drechsel (IMP), and Marcus J. Taylor (MPI IB) for constructive criticism and comments on the manuscript and Helena Jambor for constructive comments on figure design. We thank the AMBIO imaging facility (Charité, Berlin) and Nikon at MBL for imaging support, Aliona Bogdanova and Barbara Borgonovo (MPI CBG) for their help with protein purification, and Francois Nedelec (University of Cambridge) for help with Cytosim. We are grateful to the Görlich lab (MPI BPC), in particular Bastian Hülsmann and Jens Krull, and the NXR for supply with X. tropicalis frogs. We thank Antonina Roll-Mecak (National Institute of Neurological Disorders and Stroke) for help with mass spectrometry analysis and discussions and Duck-Yeon Lee in the Biochemistry Core (National Heart, Lung and Blood Institute) for access to mass spectrometers. For mass spectrometry, we would like to acknowledge the assistance of Benno Kuropka and Chris Weise from the Core Facility BioSupraMol supported by the Deutsche Forschungsgemeinschaft (DFG). We thank all former and current members of the Reber lab for discussion and helpful advice, in particular, Christoph Hentschel and Soma Zsoter for technical assistance and Sebastian Reusch for help with tubulin purification. S.R. acknowledges funding from the IRI Life Sciences (Humboldt-Universität zu Berlin, Excellence Initiative/DFG). W.G.H. was supported by the Alliance Berlin Canberra co-funded by a grant from the Deutsche Forschungsgemeinschaft (DFG) for the International Research Training Group (IRTG) 2290 and the Australian National University. K.K.M. was supported by funds in the Roll-Mecak lab, intramural program of the National Institute of Neurological Disorders and Stroke.
    Keywords: Spindle scaling ; Tubulin ; Microtubule dynamics ; Xenopus ; Spindle length
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  • 14
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marty, B., Almayrac, M., Barry, P. H., Bekaert, D., V., Broadley, M. W., Byrne, D. J., Ballentine, C. J., & Caracausi, A. An evaluation of the C/N ratio of the mantle from natural CO2-rich gas analysis: Geochemical and cosmochemical implications. Earth and Planetary Science Letters, 551, (2020): 116574, doi:10.1016/j.epsl.2020.116574.
    Description: The terrestrial carbon to nitrogen ratio is a key geochemical parameter that can provide information on the nature of Earth's precursors, accretion/differentiation processes of our planet, as well as on the volatile budget of Earth. In principle, this ratio can be determined from the analysis of volatile elements trapped in mantle-derived rocks like mid-ocean ridge basalts (MORB), corrected for fractional degassing during eruption. However, this correction is critical and previous attempts have adopted different approaches which led to contrasting C/N estimates for the bulk silicate Earth (BSE) (Marty and Zimmermann, 1999; Bergin et al., 2015). Here we consider the analysis of CO2-rich gases worldwide for which a mantle origin has been determined using noble gas isotopes in order to evaluate the C/N ratio of the mantle source regions. These gases experienced little fractionation due to degassing, as indicated by radiogenic 4He / 40Ar* values (where 4He and 40Ar* are produced by the decay of U+Th, and 40K isotopes, respectively) close to the mantle production/accumulation values. The C/N and C/3 He ratios of gases investigated here are within the range of values previously observed in oceanic basalts. They point to an elevated mantle C/N ratio (∼350-470, molar) higher than those of potential cosmochemical accretionary endmembers. For example, the BSE C/N and 36 Ar / N ratios (160-220 and 75 x 10-7, respectively) are higher than those of CM-CI chondrites but within the range of CV-CO groups. This similarity suggests that the Earth accreted from evolved planetary precursors depleted in volatile and moderately volatile elements. Hence the high C / N composition of the BSE may be an inherited feature rather than the result of terrestrial differentiation. The C / N and 36 Ar / N ratios of the surface (atmosphere plus crust) and of the mantle cannot be easily linked to any known chondritic composition. However, these compositions are consistent with early sequestration of carbon into the mantle (but not N and noble gases), permitting the establishment of clement temperatures at the surface of our planet.
    Description: M.A, D.V.B, M.W.B, D.J.B and B.M were supported by the European Research Council (PHOTONIS project, grant agreement No. 695618 to B.M.). Samples were collected as part of Study # YELL-08056 - Xenon anomalies in the Yellowstone Hotspot. We would like to thank Annie Carlson and all of the rangers at the Yellowstone National Park for providing invaluable advice and help when collecting the samples. This work was partially supported by a grant (G-2016-7206) from the Alfred P. Sloan Foundation and the Deep Carbon Observatory to P.H.B as well as NSF award 2015789 to P.H.B.. Sampling at Mt. Etna and gas analysis was supported by Instituto Nazionale di Geofisica e Vulcanologia Palermo. Fruitful discussions with Marc Hirschmann helped us to shape the ideas presented in this work. We acknowledge detailed and insightful reviews by Sami Mikhail and an anonymous reviewer, and efficient editing by Frederic Moynier. This is CRPG contribution 2741.
    Keywords: Carbon ; Nitrogen ; Earth ; Mantle ; Gases
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  • 15
    Publication Date: 2022-06-09
    Description: Joint analysis of high-penetration multi-channel and high-resolution single-channel seismic reflection profiles, calibrated by deep well boreholes, allowed a detailed reconstruction of the Late Miocene to Recent tectonic history of the Capo Granitola and Sciacca fault systems offshore southwestern Sicily. These two fault arrays are part of a regional system of transcurrent faults that dissect the foreland block in front of the Neogene Sicilian fold and thrust belt. The Capo Granitola and Sciacca faults are thought to reactivate inherited Mesozoic to Miocene normal faults developed on the northern continental margin of Africa. During Latest Miocene-Pliocene, the two ~NNE-SSW striking faults were active in left transpression, which inverted Late Miocene extensional half-grabens and created push-up ridges along both systems. Tectonic activity decreased during the Pleistocene, but transpressional folds deform Middle-Late Pleistocene sediments as well, suggesting that the two fault systems are active. The ~40 km long longitudinal amplitude profile of 1st order folds (Capo Granitola and Sciacca anticlines) shows ~15–20 km bell-shaped undulations that represents 2nd order folds. The length of these undulations together with the map pattern of faults allowed to divide the CGFS and SFS into two segments, northern and southern, respectively. Total uplift of the Sciacca Anticline is twice than the uplift of the Capo Granitola Anticline. Incremental fold growth rates decreased during time from 0.22 mm/yr (Capo Granitola Anticline) and 0.44 mm/yr (Sciacca Anticline) in the Pliocene, to 0.07 and 0.22 mm/yr, respectively, during the last ~1.8 Ma.
    Description: Published
    Description: 187-204
    Description: 2T. Deformazione crostale attiva
    Description: 3A. Geofisica marina e osservazioni multiparametriche a fondo mare
    Description: JCR Journal
    Keywords: Multiscale analysis ; Basin inversion ; Strike-slip faults ; Fold growth rates ; Pelagian foreland ; SW Sicily offshore ; 04.07. Tectonophysics ; 04.04. Geology ; 04.02. Exploration geophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 16
    Publication Date: 2022-06-14
    Description: Observations from satellites provide high-resolution images of ground deformation allowing to infer deformation sources by developing advanced modeling of magma ascent and intrusion processes. Nevertheless, such models can be strongly biased without a precise model of the internal structure of the volcano. In this study, we jointly exploited two interferometric techniques to interpret the 2011–2013 unrest at Campi Flegrei caldera (CFc). The first is the Interferometric Synthetic Aperture Radar (InSAR) technique, which provides highly-resolved spatial and temporal images of ground deformation. The second is the Ambient Noise Tomography (ANT), which images subsurface structures, providing the constraints necessary to infer the depth of the shallow source at CFc (between 0.8 and 1.2 km). We applied for the first time a tool to delineate the deformation source boundaries from the observed deformation maps: the Total Horizontal Derivative (THD) technique. The THD processes the vertical component of the ground deformation field detected through InSAR applied to COSMO-SkyMed data. The patterns retrieved by applying the THD technique show consistent spatial correlations with (1) the seismic group-velocity maps achieved through the ANT and (2) the distribution of the earthquakes nucleated during the unrest at ~1 km. High-velocity anomalies, the retrieved geometrical features of the deformation field, and the spatial distribution of seismicity coincide with extinct volcanic vents in the eastern part of the caldera (Solfatara/ Pisciarelli and Astroni). Such a coincidence hints at a significant role of the extinct plumbing system in either constraining or channeling the eastward propagation of magmatic fluids. Here, we demonstrated that a joint analysis of the InSAR patterns, seismic structures, and seismicity allows us to model in space and time the characteristics and nature of the shallow deformation source at CFc. Using published literature, we show that the effects of structural heterogeneities at shallow depths may have a more significant early-stage impact on the evolution of the surface displacement signals than deeper magmatic sources: these secondary structural effects may produce local amplification in the deformation records which can be mistakenly interpreted as early signals of impending eruptions. The achieved results are particularly relevant for the understanding of the origin of deformation signal at volcanoes where magma propagation within sills is expected, as at CFc.
    Description: Published
    Description: 111440
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: JCR Journal
    Keywords: InSAR ; Ambient noise tomography ; Total horizontal derivative ; Campi Flegrei caldera ; Natural seismicity
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 17
    Publication Date: 2022-06-10
    Description: Active lava lakes represent a variety of open-vent volcanism in which a sizable body of lava accumulates at the top of the magma column, constrained by the vent and/or crater geometry. The longevity of lava lakes reflects a balancing of cooling and outgassing occurring at the surface and input of hot and gas-rich magma from below. Due to their longevity and relative accessibility, lava lakes provide a natural laboratory for studying fundamental volcanic processes such as degassing, convection and cooling. This article examines all seven lakes that existed at the time of writing in 2018, located in the Pacific, Antarctica, Africa, and South and Central America. These lakes span all tectonic environments, and a range of magma compositions. We focus on analysis of the lake surface motion using image velocimetry, which reveals both similarities and contrasts in outgassing and lake dynamics when comparing the different lakes. We identify two categories of lake behavior: Organized (Erta’Ale, Nyiragongo, Kīlauea after 2011, and Erebus) and Chaotic (Villarrica, Masaya, Marum). This division does not map directly to lake size, viscosity, gas emission rate, or temperature. Instead, when examined together, we find that the lakes follow a linear relationship between average surface speed and the ratio of total gas flux to lake surface area. This relationship points to the combined importance of both flux and lake size in addition to the total volume of gas emission, and suggests that a shared deep mechanism controls the supply of heat and gas to all lakes. On the other hand, the differences between Chaotic and Organized lakes highlight the important role of the geometry of the conduit-lake transition, which superimposes a shallow signal on that of the deep circulation. The spatial patterns of surface motion we document suggest that the release of gas bubbles at Chaotic lakes is more efficient (i.e., bubbles are less likely to be retained and recycled) compared with Organized lakes. In addition, the data presented here indicate that the solidified crust of Organized lakes plays a role in regulating convection and outgassing in lava lakes.
    Description: Published
    Description: 16-31
    Description: 5V. Processi eruttivi e post-eruttivi
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 18
    Publication Date: 2022-06-09
    Description: A 3D crustal density model for Egypt was compiled. It is constrained by available deep seismic refraction, receiver functions analysis, borehole, and geological data. In Egypt, seismic data are sparsely and irregularly distributed. Consequently, we developed the crustal thickness model by integrating seismic and gravity data. Satellite gravity data was inverted to build an initial model, which was followed by a detailed 3D forward gravity modelling. The initial crustal thickness is determined by applying seismically constrained non-linear inversion, based on the modified Bott's method and Tikhonov regularization assuming spherical Earth approximation. Moreover, the gravity inversion-based Moho depth estimates are in good agreement with results of seismic studies and are exploited for the 3D forward modelling. Crustal thicknesses range from 25 to 30 km along the rifted margins of the Red Sea, which thin toward the Mediterranean Sea. Thicknesses in southern Egypt reach values between 35 and 40 km. A maximum crustal thickness of 45 km is found in the southwestern part of Egypt. Within the Sinai Peninsula, the thickness varies from the shallow southern edge (∼ 31 km) and increases toward the North (∼ 36 km). Our model revealed a thick lower crust beneath the southern part of Egypt, which can be associated with crustal modification that occurred during the collision of East Gondwana and the Saharan Metacraton along the Keraf suture zone during the final assembly of Gondwana in the Neoproterozoic. Finally, the isostatic implications of the differences between the seismic and gravity-derived Mohos are thoroughly discussed. In conclusion, the developed 3D crustal thickness model provides high-resolution Moho depth estimates that closely resembles the major geological and tectonic features. Also, the existing correlation between the topography, Bouguer anomalies, and Moho depths indicates that the investigated area is close to its isostatic equilibrium.
    Description: Published
    Description: 52-67
    Description: 2TR. Ricostruzione e modellazione della struttura crostale
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 19
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rastetter, E. B., & Kwiatkowski, B. L. An approach to modeling resource optimization for substitutable and interdependent resources. Ecological Modelling, 425, (2020): 109033, doi:10.1016/j.ecolmodel.2020.109033.
    Description: We develop a hierarchical approach to modeling organism acclimation to changing availability of and requirements for substitutable and interdependent resources. Substitutable resources are resources that fill the same metabolic or stoichiometric need of the organism. Interdependent resources are resources whose acquisition or expenditure are tightly linked (e.g., light, CO2, and water in photosynthesis and associated transpiration). We illustrate the approach by simulating the development of vegetation with four substitutable sources of N that differ only in the cost of their uptake and assimilation. As the vegetation develops, it uses the least expensive N source first then uses progressively more expensive N sources as the less expensive sources are depleted. Transition among N sources is based on the marginal yield of N per unit effort expended, including effort expended to acquire C to cover the progressively higher uptake costs. We illustrate the approach to interdependent resources by simulating the expenditure of effort to acquire light energy, CO2, and water to drive photosynthesis in vegetation acclimated to different conditions of soil water, atmospheric vapor pressure deficit, CO2 concentration, and light levels. The approach is an improvement on the resource optimization used in the earlier Multiple Element Limitation (MEL) model.
    Description: This work was supported in part by the National Science Foundation under NSF grants 1651722, 1637459, 1603560, 1556772, 1841608. Any Opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the National Science Foundation.
    Keywords: Resource optimization ; Acclimation ; Substitutable resources ; Interdependent resources ; Resource limitation ; Multiple resource limitation
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  • 20
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Trathan, P. N., Wienecke, B., Barbraud, C., Jenouvrier, S., Kooyman, G., Le Bohec, C., Ainley, D. G., Ancel, A., Zitterbart, D. P., Chown, S. L., LaRue, M., Cristofari, R., Younger, J., Clucas, G., Bost, C., Brown, J. A., Gillett, H. J., & Fretwell, P. T. The emperor penguin - vulnerable to projected rates of warming and sea ice loss. Biological Conservation, 241, (2020): 108216, doi:10.1016/j.biocon.2019.108216.
    Description: We argue the need to improve climate change forecasting for ecology, and importantly, how to relate long-term projections to conservation. As an example, we discuss the need for effective management of one species, the emperor penguin, Aptenodytes forsteri. This species is unique amongst birds in that its breeding habit is critically dependent upon seasonal fast ice. Here, we review its vulnerability to ongoing and projected climate change, given that sea ice is susceptible to changes in winds and temperatures. We consider published projections of future emperor penguin population status in response to changing environments. Furthermore, we evaluate the current IUCN Red List status for the species, and recommend that its status be changed to Vulnerable, based on different modelling projections of population decrease of ≥50% over the current century, and the specific traits of the species. We conclude that current conservation measures are inadequate to protect the species under future projected scenarios. Only a reduction in anthropogenic greenhouse gas emissions will reduce threats to the emperor penguin from altered wind regimes, rising temperatures and melting sea ice; until such time, other conservation actions are necessary, including increased spatial protection at breeding sites and foraging locations. The designation of large-scale marine spatial protection across its range would benefit the species, particularly in areas that have a high probability of becoming future climate change refugia. We also recommend that the emperor penguin is listed by the Antarctic Treaty as an Antarctic Specially Protected Species, with development of a species Action Plan.
    Description: We thank Thomas J. Bracegirdle, Tony Phillips and Kevin Hughes for helpful comments on earlier drafts of this manuscript. PNT acknowledges the support of WWF-UK under GB095701 and SJ the support of NSF OPP1744794 and 1643901.
    Keywords: Antarctic ; Climate change ; Aptenodytes forsteri ; IUCN Red List threat status ; Protection ; Conservation
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  • 21
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Jin, D., Hoagland, P., & Buesseler, K. O. The value of scientific research on the ocean's biological carbon pump. Science of the Total Environment, 749, (2020): 141357, doi:10.1016/j.scitotenv.2020.141357.
    Description: The ocean's biological carbon pump (BCP) sequesters carbon from the surface to the deep ocean and seabed, constituting one of Earth's most valuable ecosystem services. Significant uncertainty exists surrounding the amounts and rates of organic carbon sequestered in the oceans, however. With improved understanding of BCP sequestration, especially its scale, world policymakers would be positioned to make more informed decisions regarding the mitigation of carbon emissions. Here, an analytical model of the economic effects of global carbon emissions—including scientific uncertainty about BCP sequestration—was developed to estimate the value of marine scientific research concerning sequestration. The discounted net economic benefit of a putative 20-year scientific research program to narrow the range of uncertainty around the amount of carbon sequestered in the ocean is on the order of $0.5 trillion (USD), depending upon the accuracy of predictions, the convexities of climate damage and economic output functions, and the initial range of uncertainty.
    Description: This research is supported by WHOI's Ocean Twilight Zone program which is part of the Audacious Project, a collaborative endeavor, housed at TED. DJ was also funded by National Oceanic and Atmospheric Administration (NOAA) Cooperative Institutes (CINAR) award NA14OAR4320158. KB was also funded by National Aeronautics and Space Administration (NASA) as part of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) program award 80NSSC17K0555. We thank Ankur Shah for research assistance and three anonymous reviewers for their constructive suggestions.
    Keywords: Economic value of scientific research ; Value of information ; Biological carbon pump ; Carbon sequestration ; Ecosystem service ; Ocean twilight zone
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  • 22
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Brothers, L. L., Foster, D. S., Pendleton, E. A., & Baldwin, W. E. Seismic stratigraphic framework of the continental shelf offshore Delmarva, USA: implications for Mid-Atlantic Bight evolution since the Pliocene. Marine Geology, 428, : (2020)106287, doi:10.1016/j.margeo.2020.106287.
    Description: Understanding how past coastal systems have evolved is critical to predicting future coastal change. Using over 12,000 trackline kilometers of recently collected, co-located multi-channel boomer, sparker and chirp seismic reflection profile data integrated with previously collected borehole and vibracore data, we define the upper (〈 115 m below mean lower low water) seismic stratigraphic framework offshore of the Delmarva Peninsula, USA. Twelve seismic units and 11 regionally extensive unconformities (U1-U11) were mapped over 5900 km2 of North America's Mid-Atlantic continental shelf. We interpret U3, U7, U9, U11 as transgressive ravinement surfaces, while U1,2,4,5,6,8,10 are subaerial unconformities illustrating distinct periods of lower sea-level. Based on areal distribution, stratigraphic relationships and dating results (Carbon 14 and amino acid racemization estimates) from earlier vibracore and borehole studies, we interpret the infilled channels as late Neogene and Quaternary courses of the Susquehanna, Potomac, Rappahannock, York, James rivers and tributaries, and a broad flood plain. These findings indicate that the region's geologic framework is more complex than previously thought and that Pleistocene paleochannels are abundant in the Mid-Atlantic. This study synthesizes and correlates the findings of other Atlantic Margin studies and establishes a large-scale Quaternary framework that enables more detailed stratigraphic analysis in the future. Such work has implications for inner continental shelf systems tract evolution, the relationship between antecedent geology and modern coastal systems, assessments of eustacy, glacial isostatic adjustment, and other processes and forcings that play a role in passive margin evolution.
    Description: This work was supported by the U.S. Department of the Interior's Response to Hurricane Sandy.
    Keywords: N Atlantic ; Shelf (morphology and stratigraphy) ; Quaternary stratigraphy ; Paleochannels ; Geophysics (seismic)
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  • 23
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lin, H. T., Hsieh, C. C., Repeta, D. J., & Rappé, M. S. Sampling of basement fluids via circulation obviation retrofit kits (CORKs) for dissolved gases, fluid fixation at the seafloor, and the characterization of organic carbon. Methodsx, 7, (2020): 101033, doi:10.1016/j.mex.2020.101033.
    Description: The advanced instrumented GeoMICROBE sleds (Cowen et al., 2012) facilitate the collection of hydrothermal fluids and suspended particles in the subseafloor (basaltic) basement through Circulation Obviation Retrofit Kits (CORKs) installed within boreholes of the Integrated Ocean Drilling Program. The main components of the GeoMICROBE can be converted into a mobile pumping system (MPS) that is installed on the front basket of a submersible or remotely-operated-vehicle (ROV). Here, we provide details of a hydrothermal fluid-trap used on the MPS, through which a gastight sampler can withdraw fluids. We also applied the MPS to demonstrate the value of fixing samples at the seafloor in order to determine redox-sensitive dissolved iron concentrations and speciation measurements. To make the best use of the GeoMICROBE sleds, we describe a miniature and mobile version of the GeoMICROBE sled, which permits rapid turn-over and is relatively easy for preparation and operation. Similar to GeoMICROBE sleds, the Mobile GeoMICROBE (MGM) is capable of collecting fluid samples, filtration of suspended particles, and extraction of organics. We validate this approach by demonstrating the seafloor extraction of hydrophobic organics from a large volume (247L) of hydrothermal fluids. • We describe the design of a hydrothermal fluid-trap for use with a gastight sampler, as well as the use of seafloor fixation, through ROV- or submersible assisted mobile pumping systems. • We describe the design of a Mobile GeoMICROBE (MGM) that enhances large volume hydrothermal fluid sampling, suspended particle filtration, and organic matter extraction on the seafloor. • We provide an example of organic matter extracted and characterized from hydrothermal fluids via a MGM.
    Description: We dedicate this work to Dr. James P. Cowen, who had envisioned and constructed the integrated instrumentation, GeoMICROBE, to monitor the sub-basement biosphere. We thank the chief scientists, captains, crews, and science teams on board R/V Atlantis cruises AT15-35, AT15-51, AT15-66, AT18-07, MSM20-5, AT26-03, and AT26-18, and the pilots and crews of ROV Jason II and HOV Alvin. We thank our student assistants, Natalie Hamada, Kathryn Hu, Ryan Matzumoto, Everette Omori, and Fan-Chieh Chuang. This work was supported by the National Science Foundation-Microbial Observatory Project (NSF-MCB06-04014 to J. P. Cowen), Center for Dark Energy Biosphere Investigations (C-DEBI; NSF award OCE-0939564 to M. S. Rappé), NSF award OCE-1260723 (to M. S. Rappé), and the Ministry of Science and Technology of Taiwan award (MOST 105-2119-M-002-034, MOST 107-2611-M-002-002, MOST 108-2611-M-002-006, and MOST109-2611-M-002-008 to H.-T. Lin). Ministry of Education (MOE) Republic of China (Taiwan) 109L892601 to H.-T. Lin. NSF award OCE-1634080 (to D. J. Repeta), the Simons Foundation-Simons Collaboration on Ocean Processes and Ecology (SCOPE) award 329108 (to D. J. Repeta), the Gordon and Betty Moore Foundation award 6000 (to D. J. Repeta). This paper is SOEST contribution number 11121, HIMB contribution 1804 and C-DEBI contribution number 543.
    Keywords: GeoMICROBE ; Hydrothermal fluid ; Crustal fluid ; Mobile pumping system ; Helium ; Methane ; Dissolved organic matter ; Extraction and preconcentration ; Deep subseafloor
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  • 24
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Arenas Gomez, C. M., Woodcock, M. R., Smith, J. J., Voss, S. R., & Delgado, J. P. A de novo reference transcriptome for Bolitoglossa vallecula, an Andean mountain salamander in Colombia. Data in Brief, 29, (2020): 105256, doi:10.1016/j.dib.2020.105256.
    Description: The amphibian order Caudata, contains several important model species for biological research. However, there is need to generate transcriptome data from representative species of the primary salamander families. Here we describe a de novo reference transcriptome for a terrestrial salamander, Bolitoglossa vallecula (Caudata: Plethodontidae). We employed paired-end (PE) illumina RNA sequencing to assemble a de novo reference transcriptome for B. vallecula. Assembled transcripts were compared against sequences from other vertebrate taxa to identify orthologous genes, and compared to the transcriptome of a close plethodontid relative (Bolitoglossa ramosi) to identify commonly expressed genes in the skin. This dataset should be useful to future comparative studies aimed at understanding important biological process, such as immunity, wound healing, and the production of antimicrobial compounds.
    Description: This work was funded by a research grant from COLCIENCIAS 569 (GRANT 027-2103) and CODI (Programa Sostenibilidad) 2013–2014 of the University of Antioquia. A PhD fellowship to the first author, Claudia Arenas was funded by the COLCIENCIAS 567 Grant. We thank the lab of Juan Fernando Alzate from the University of Antioquia for their help in developing our bioinformatic methodological approach. We thank Andrea Gómez and Melisa Hincapie for their help in animal collection and husbandry.
    Keywords: Bolitoglossa ; Plethodontid ; Salamanders ; Skin ; Transcriptomics
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  • 25
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Li, Y., Stumpf, R. P., McGillicuddy, D. J.,Jr, & He, R. Dynamics of an intense Alexandrium catenella red tide in the Gulf of Maine: satellite observations and numerical modeling. Harmful Algae, 99, (2020): 101927, doi:10.1016/j.hal.2020.101927.
    Description: In July 2009, an unusually intense bloom of the toxic dinoflagellate Alexandrium catenella occurred in the Gulf of Maine. The bloom reached high concentrations (from hundreds of thousands to one million cells L−1) that discolored the water and exceeded normal bloom concentrations by a factor of 1000. Using Medium Resolution Imaging Spectrometer (MERIS) imagery processed to target chlorophyll concentrations (〉2 µg L−1), patches of intense A. catenella concentration were identified that were consistent with the highly localized cell concentrations observed from ship surveys. The bloom patches were generally aligned with the edge of coastal waters with high-absorption. Dense bloom patches moved onshore in response to a downwelling event, persisted for approximately one week, then dispersed rapidly over a few days and did not reappear. Coupled physical-biological model simulations showed that wind forcing was an important factor in transporting cells onshore. Upward swimming behavior facilitated the horizontal cell aggregation, increasing the simulated maximum depth-integrated cell concentration by up to a factor of 40. Vertical convergence of cells, due to active swimming of A. catenella from the subsurface to the top layer, could explain the additional 25-fold intensification (25 × 40=1000-fold) needed to reach the bloom concentrations that discolored the water. A model simulation that considered upward swimming overestimated cell concentrations downstream of the intense aggregation. This discrepancy between model and observed concentrations suggested a loss of cells from the water column at a time that corresponded to the start of encystment. These results indicated that the joint effect of upward swimming, horizontal convergence, and wind-driven flow contributed to the red water event, which might have promoted the sexual reproduction event that preceded the encystment process.
    Description: DJM gratefully acknowledges support of the Woods Hole Center for Oceans and Human Health, funded jointly by the National Science Foundation (OCE-1314642 and OCE-1840381) the National Institute of Environmental Health Sciences (P01ES021923–01 and P01 ES028938–01). RH acknowledges support made possible by NOAA grant NA15NOS4780196 and NA16NOS0120028.
    Keywords: Red water ; Bloom patches ; Cell accumulation ; Coastal upwelling ; Upward swimming
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  • 26
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kantha, L., Weller, R. A., Farrar, J. T., Rahaman, H., & Jampana, V. A note on modeling mixing in the upper layers of the Bay of Bengal: importance of water type, water column structure and precipitation. Deep-Sea Research Part II-Topical Studies in Oceanography, 168, (2019): 104643. doi: 10.1016/j.dsr2.2019.104643.
    Description: Turbulent mixing in the upper layers of the northern Bay of Bengal is affected by a shallow layer overlying the saline waters of the Bay, which results from the huge influx of freshwater from major rivers draining the Indian subcontinent and from rainfall over the Bay during the summer monsoon. The resulting halocline inhibits wind-driven mixing in the upper layers. The brackish layer also alters the optical properties of the water column. Air-sea interaction in the Bay is expected to play a significant role in the intraseasonal variability of summer monsoons over the Indian subcontinent, and as such the sea surface temperature (SST) changes during the summer monsoon are of considerable scientific and societal importance. In this study, data from the heavily instrumented Woods Hole Oceanographic Institution (WHOI) mooring, deployed at 18oN, 89.5oE in the northern Bay from December 2014 to January 2016, are used to drive a one-dimensional mixing model, based on second moment closure model of turbulence, to explore the intra-annual variability in the upper layers. The model results highlight the importance of the optical properties of the upper layers (and hence the penetration of solar insolation in the water column), as well as the temperature and salinity in the upper layers prescribed at the start of the model simulation, in determining the SST in the Bay during the summer monsoon. The heavy rainfall during the summer monsoon also plays an important role. The interseasonal and intraseasonal variability in the upper layers of the Bay are contrasted with those in the Arabian Sea, by the use of the same model but driven by data from an earlier deployment of a WHOI mooring in the Arabian Sea at 15.5 oN, 61.5 oE from December 1994 to December 1995.
    Description: LK was supported by U.S. Office of Naval Research (ONR) MISO/BoB DRI under grant number N00014-17-1-2716. RW and JTF were supported by ONR Grants N00014-13-1-0453 and N00014-17-1-2880, and the WHOI mooring was funded by Grant N00014-13-1-0453. RW was supported by ONR for the 1994–1995 deployment of the surface mooring in the Arabian Sea. HR and VJ wish to thank Dr. SSC Shenoi, the Director of INCOIS and Dr. M Ravichandran, Director, NCPOR for the encouragement and support to carry out this study. This work was supported by the Ministry of Earth Sciences (MoES), Govt. of India. This is also INCOIS Contribution number 349.
    Keywords: Bay of Bengal ; Arabian sea ; Mixing in the upper layers ; Second moment closure ; Turbulence ; WHOI mooring ; OMNI mooring ; Water type ; Solar insolation ; Precipitation
    Repository Name: Woods Hole Open Access Server
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  • 27
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Schwing, F. B., Sissenwine, M. J., Batchelder, H., Dam, H. G., Gomez-Gutierrez, J., Keister, J. E., Liu, H., & Peterson, J. O. William (Bill) Peterson's contributions to ocean science, management, and policy. Progress in Oceanography, 182, (2020): 102241, doi:10.1016/j.pocean.2019.102241.
    Description: In addition to being an esteemed marine ecologist and oceanographer, William T. (Bill) Peterson was a dedicated public servant, a leader in the ocean science community, and a mentor to a generation of scientists. Bill recognized the importance of applied science and the need for integrated “big science” programs to advance our understanding of ecosystems and to guide their management. As the first US GLOBEC program manager, he was pivotal in transitioning the concept of understanding how climate change impacts marine ecosystems to an operational national research program. The scientific insight and knowledge generated by US GLOBEC informed and advanced the ecosystem-based management approaches now being implemented for fishery management in the US. Bill held significant leadership roles in numerous international efforts to understand global and regional ecological processes, and organized and chaired a number of influential scientific conferences and their proceedings. He was passionate about working with and training young researchers. Bill’s academic affiliations, notably at Stony Brook and Oregon State Universities, enabled him to advise, train, and mentor a host of students, post-doctoral researchers, and laboratory technicians. Under his collegial guidance they became critical independent thinkers and diligent investigators. His former students and colleagues carry on Bill Peterson’s legacy of research that helps us understand marine ecosystems and informs more effective resource stewardship and conservation.
    Repository Name: Woods Hole Open Access Server
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  • 28
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McCollom, T. M., Klein, F., Moskowitz, B., Berquo, T. S., Bach, W., & Templeton, A. S. Hydrogen generation and iron partitioning during experimental serpentinization of an olivine-pyroxene mixture. Geochimica Et Cosmochimica Acta, 282, (2020): 55-75, doi:10.1016/j.gca.2020.05.016.
    Description: A series of laboratory experiments was conducted to investigate serpentinization of olivine–pyroxene mixtures at 230 °C, with the objective of evaluating the effect of mixed compositions on Fe partitioning among product minerals, H2 generation, and reaction rates. An initial experiment reacted a mixture of 86 wt.% olivine and 14 wt.% orthopyroxene (Opx) with the same initial grain size for 387 days. The experiment resulted in extensive reaction (∼53% conversion), and solids recovered at termination of the experiment were dominated by Fe-bearing chrysotile and relict olivine along with minor brucite and magnetite. Only limited amounts of H2 were generated during the first ∼100 days of the experiment, but the rate of H2 generation then increased sharply coincident with an increase in pH from mildly alkaline to strongly alkaline conditions. Two shorter term experiments with the same reactants (26 and 113 days) produced a mixture of lizardite and talc that formed a thin coating on relict olivine and Opx grains, with virtually no generation of H2. Comparison of the results with reaction path models indicates that the Opx reacted about two times faster than olivine, which contrasts with some previous studies that suggested olivine should react more rapidly than Opx at the experimental conditions. The models also indicate that the long-term experiment transitioned from producing serpentine ± talc early in the early stages to precipitation of serpentine plus magnetite, with brucite beginning to precipitate only late in the experiment as Opx was depleted. The results indicate that overall reaction of olivine and Opx was initially relatively slow, but reaction rates accelerated substantially when the pH transitioned to strongly alkaline conditions. Serpentine and brucite precipitated from the olivine-Opx mixture had higher Fe contents than observed in olivine-only experiments at mildly alkaline pH, but had comparable Fe contents to reaction of olivine at strongly alkaline pH implying that higher pH may favor greater partitioning of Fe into serpentine and brucite and less into magnetite. Despite the presence of brucite, dissolved silica activities during the long-term olivine-Opx experiment maintained levels well above serpentine-brucite equilibrium. Instead, silica activities converged on levels close to metastable equilibrium between brucite and olivine. It is proposed that silica levels during the experiment may have been regulated by exchange of SiO2 between the fluid and a silica-depleted, brucite-like surface layer on dissolving olivine.
    Description: This research was supported by the U. S. National Science Foundation Marine Geology and Geophysics program through grant NSF-OCE 0927744 and by the NASA Astrobiology Institute through Cooperative Agreement NNA15BB02A. Additional support to TMM from the Hanse Wissenschaftskolleg (Delmenhorst, Germany) at an early stage of this project is gratefully acknowledged. FK acknowledges support through Grant NSF-OCE 1427274. The IRM is supported by the Instruments and Facilities Program of the NSF Division of Earth Science. This is IRM contribution 1711. We very much appreciate the comments of Fabrice Brunet, Gleb Pokrovski and an anonymous reviewer that helped us refine our interpretations and improve communication of the results.
    Repository Name: Woods Hole Open Access Server
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  • 29
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Babbin, A. R., Buchwald, C., Morel, F. M. M., Wankel, S. D., & Ward, B. B. Nitrite oxidation exceeds reduction and fixed nitrogen loss in anoxic Pacific waters. Marine Chemistry, 224, (2020): 103814, doi:10.1016/j.marchem.2020.103814.
    Description: The diversity of nitrogen-based dissimilatory metabolisms in anoxic waters continues to increase with additional studies to the marine oxygen deficient zones (ODZs). Although the microbial oxidation of nitrite (NO2–) has been known for over a century, studies of the pathways and microbes involved have generally proceeded under the assumption that nitrite oxidation to nitrate requires dioxygen (O2). Anaerobic NO2– oxidation until now has been conclusively shown only for anammox bacteria, albeit only as a limited sink for NO2– in their metabolism compared to the NO2– reduced to N2. Here, using direct experimental techniques optimized for replicating in situ anoxic conditions, we show that NO2– oxidation is substantial, widespread, and consistent across the ODZs of the eastern tropical Pacific Ocean. Regardless of the specific oxidant, NO2– oxidation rates are up to an order of magnitude larger than simultaneous N2 production rates for which these zones are known, and cannot be explained by anammox rates alone. Higher rates of NO2– oxidation over reduction in anoxic waters are paradoxical but help to explain how anammox rates can be enhanced over denitrification in shallow anoxic waters (σθ 〈 26.4) at the edge of the ODZs but not within the ODZ core. Furthermore, nitrite oxidation may be the key to reconciliation of the perceived imbalance of the global fixed nitrogen loss budget.
    Description: This work was funded by National Science Foundation grants OCE–1029951 to B.B.W, BIO–1402109 to A.R.B., and OCE-1260373 to S.D.W. Additional financial support to A.R.B. was provided by Simons Foundation grant 622065 and the generous contributions of Dr. Bruce L. Heflinger.
    Keywords: Nitrogen cycling ; Oxygen deficient zones ; Nitrite oxidation ; Denitrification ; Anammox
    Repository Name: Woods Hole Open Access Server
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  • 30
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gu, S., Liu, Z., Oppo, D. W., Lynch-Stieglitz, J., Jahn, A., Zhang, J., & Wu, L. Assessing the potential capability of reconstructing glacial Atlantic water masses and AMOC using multiple proxies in CESM. Earth and Planetary Science Letters, 541, (2020): 11629, doi:10.1016/j.epsl.2020.116294.
    Description: Reconstructing the Atlantic Meridional Overturning Circulation (AMOC) during the Last Glacial Maximum (LGM) is essential for understanding glacial-interglacial climate change and the carbon cycle. However, despite many previous studies, uncertainties remain regarding the glacial water mass distributions in the Atlantic and the AMOC intensity. Here we use an isotope enabled ocean model with multiple geotracers (δ 13 C,E Νd,231 Pa/ 230Th,δ 18 Ο and Δ 14 C) and idealized water tracers to study the potential constraints on LGM ocean circulation from multiple proxies. Our model suggests that the glacial Atlantic water mass distribution can be accurately constrained by the air-sea gas exchange signature of water masses (δ13 C AS), but E Nd might overestimate the North Atlantic Deep Water (NADW) percentage in the deep Atlantic probably because of the boundary source of Nd. A sensitivity experiment with an AMOC of similar geometry but much weaker strength suggests that the correct AMOC geometry is more important than the AMOC strength for simulating the observed glacial δ13 C AS and E Nd and distributions. The kinematic tracer 231Pa/230Th is sensitive to AMOC intensity, but the interpretation might be complicated by the AMOC geometry and AABW transport changes during the LGM. δ 18 Ο in the benthic foraminifera (δ 18 Οc) from the Florida Straits provides a consistent measure of the upper ocean boundary current in the model, which potentially provides an unambiguous method to reconstruct glacial AMOC intensity. Finally, we propose that the moderate difference between AMOC intensity at LGM and PD, if any, is caused by the competition of the responses to CO2 forcing and continental ice sheet forcing.
    Description: We thank two anonymous reviewers for their useful and constructive comments. We also thank Editor Dr Laura F. Robinson for handling the manuscript. This work is supported by National Science Foundation of China No. 41630527, US National Science Foundation (NSF) P2C2 projects (1401778, 1401802, and 1566432). We would like to acknowledge the high-performance computing support from Yellowstone (ark:/85065/d7wd3xhc) and Cheyenne (doi:10.5065/D6RX99HX) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation and from Center for High Performance Computing and System Simulation, Pilot National Laboratory for Marine Science and Technology (Qingdao). Data used to produce the results in this study can be obtained from HPSS at CISL: /home/sgu28/CTRACE_decadal or by contacting the authors.
    Keywords: Last Glacial Maximum ; AMOC ; Water mass ; Multi-proxy
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  • 31
    Publication Date: 2022-01-07
    Description: The Q10 temperature coefficient, which is widely used in scientific literature, is a measure of the temperature sensitivity of chemical reaction rates or biological processes. However, the conclusions drawn from applying this coefficient to experimental data obtained from biological processes are not universal. In many biological processes, Q10 values are often discordant with the results predicted by the Arrhenius law. The hypothesis tested in the present study is that this problem arises mainly from the fact that the Q10 coefficient is defined by the ratio between rates described by exponential laws instead of power laws. Considering this hypothesis and the need to review the mathematical laws and models currently used to describe rates and Q10 coefficients, we propose a model beyond the usual Arrhenius theory or exponential decay law herein. The proposed mathematical model is based on the theory of deformed exponential functions, with the ordinary Q10 model representing the conventional exponential function. Therefore, all results following the standard model remain valid. Moreover, we include a Q10 free open-source code, written in Python, and compatible with Windows, Linux and macOS platforms. The validation of the proposed model and confirmation of the given hypothesis were performed based on the following temperature-dependent biological processes: soil organic carbon (SOC) decomposition (which is essential to forecast the impact of climate change on terrestrial ecosystems); the metabolism of Arctic zooplankton; physiological processes of the respiratory and cardiovascular systems; rate of oxygen consumption in mitochondria of the eurythermal killifish Fundulus heteroclitus, and leaf respiration.
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  • 32
    Publication Date: 2022-01-07
    Description: Since 2010, the Soil Moisture and Ocean Salinity (SMOS) satellite mission monitors the earth emission at L-Band. It provides the longest time series of Sea Surface Salinity (SSS) from space over the global ocean. However, the SSS retrieval at high latitudes is a challenge because of the low sensitivity L-Band radiometric measurements to SSS in cold waters and to the contamination of SMOS measurements by the vicinity of continents, of sea ice and of Radio Frequency Interferences. In this paper, we assess the quality of weekly SSS fields derived from swath-ordered instantaneous SMOS SSS (so called Level 2) distributed by the European Space Agency. These products are filtered according to new criteria. We use the pseudo-dielectric constant retrieved from SMOS brightness temperatures to filter SSS pixels polluted by sea ice. We identify that the dielectric constant model and the sea surface temperature auxiliary parameter used as prior information in the SMOS SSS retrieval induce significant systematic errors at low temperatures. We propose a novel empirical correction to mitigate those sources of errors at high latitudes. Comparisons with in-situ measurements ranging from 1 to 11 m depths spotlight huge vertical stratification in fresh regions. This emphasizes the need to consider in-situ salinity as close as possible to the sea surface when validating L-band radiometric SSS which are representative of the first top centimeter. SSS Standard deviation of differences (STDD) between weekly SMOS SSS and in-situ near surface salinity significantly decrease after applying the SSS correction, from 1.46 pss to 1.28 pss. The correlation between new SMOS SSS and in-situ near surface salinity reaches 0.94. SMOS estimates better capture SSS variability in the Arctic Ocean in comparison to TOPAZ reanalysis (STDD between TOPAZ and in-situ SSS = 1.86 pss), particularly in river plumes with very large SSS spatial gradients.
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  • 33
    Publication Date: 2022-01-07
    Description: The exhumation of peridotite rocks in oceanic transform zones passes by the rheological transition between the ductile and brittle deformation until the complete emplacement in the oceanic lithosphere. The São Pedro and São Paulo Archipelago (SPSPA), in the Equatorial Atlantic, records the deformational products of ductile, brittle and the rocks/fluid interaction generating specific structures in each domain. The deformational stages are related to the transpressional and transtensional geodynamics of São Paulo Transform Fault. Firstly, during transpression, exhumation occurs associated with the ductile domain causing intense mylonitization in temperatures between ~700° and 800 °C, defined by olivine and orthopyroxene recrystallization. The interaction with fluids initially originated from the mantle generates amphibole and oxide-rich layers marking the passage to a semi-brittle deformation. The continuation of peridotite exhumation, associated with an NW-SE shortening and transpressional led to a higher availability of hydrothermal fluids. As a consequence, four serpentinization episodes are recorded, which are associated with semi-brittle to brittle transition under temperatures between 300° and 400 °C. Finally, the complete exhumation and establishment of brittle mechanisms led to carbonatation phase near the surface, with temperatures ranging from 300° to 150 °C. The active NW-SE tectonic stress generated E-W strike-slip faults that were filled by carbonates recording the final exhumation stage.
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  • 34
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    Elsevier
    In:  Environmental Technology & Innovation, 17 . Art.-Nr.: 100567.
    Publication Date: 2022-01-07
    Description: The present state of constantly increasing plastic pollution is the major concern of scientific researchers. The conventional techniques applied (i.e., burning and landfilling) to get plastic degraded from the environment are inadequate due to harmful byproducts and limited to its recycling. In this review, we have recapitulated recent biotechnological approaches, including synthetic microbial consortia, systems biology tools, and genetic engineering techniques which can pave the path towards the plastic bioremediation and degradation. Moreover, potential plastic degrader microbes and their degradation pathways are also summarized. Lastly, this review focuses on enhancing the understanding of the degradation ability of microorganisms using contemporary biotechnological tools.
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  • 35
    Publication Date: 2022-01-07
    Description: Atmospheric deposition of aerosols to the ocean provides an important pathway for the supply of vital micronutrients, including trace metals. These trace metals are essential for phytoplankton growth, and therefore their delivery to marine ecosystems can strongly influence the ocean carbon cycle. The solubility of trace metals in aerosols is a key parameter to better constrain their potential impact on phytoplankton growth. To date, a wide range of experimental approaches and nomenclature have been used to define aerosol trace metal solubility, making data comparison between studies difficult. Here we investigate and discuss several laboratory leaching protocols to determine the solubility of key trace metals in aerosol samples, namely iron, cobalt, manganese, copper, lead, vanadium, titanium and aluminium. Commonly used techniques and tools are also considered such as enrichment factor calculations and air mass back-trajectory projections and recommendations are given for aerosol field sampling, laboratory processing (including leaching and digestion) and analytical measurements. Finally, a simple 3-step leaching protocol combining commonly used protocols is proposed to operationally define trace metal solubility in aerosols. The need for standard guidelines and protocols to study the biogeochemical impact of atmospheric trace metal deposition to the ocean has been increasingly emphasised by both the atmospheric and oceanographic communities. This lack of standardisation currently limits our understanding and ability to predict ocean and climate interactions under changing environmental conditions.
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  • 36
    Publication Date: 2022-01-07
    Description: Highlights • Regional brain iron concentrations are heterogenous. • Regional distribution of iron is most consistent with ferritin mRNA expression. • SEC-ICP-MS reveals the protein masses that cytosolic iron is associated with. • More than 50 % of cytosolic iron is associated with ferritin. Iron is essential for brain development and health where its redox properties are used for a number of neurological processes. However, iron is also a major driver of oxidative stress if not properly controlled. Brain iron distribution is highly compartmentalised and regulated by a number of proteins and small biomolecules. Here, we examine heterogeneity in regional iron levels in 10 anatomical structures from seven post-mortem human brains with no apparent neuropathology. Putamen contained the highest levels, and most case-to-case variability, of iron compared with the other regions examined. Partitioning of iron between cytosolic and membrane-bound iron was generally consistent in each region, with a slightly higher proportion (55 %) in the ‘insoluble’ phase. We expand on this using the Allen Human Brain Atlas to examine patterns between iron levels and transcriptomic expression of iron regulatory proteins and using quantitative size exclusion chromatography-inductively coupled plasma-mass spectrometry to assess regional differences in the molecular masses to which cytosolic iron predominantly binds. Approximately 60 % was associated with ferritin, equating to approximately 25 % of total tissue iron essentially in storage. This study is the first of its kind in human brain tissue, providing a valuable resource and new insight for iron biologists and neuroscientists, alike.
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  • 37
    Publication Date: 2022-01-07
    Description: The aim of this study was to investigate the syntrophic methanogenesis from the perspective of energy transfer and competition. Effects of redox materials and redox potential on direct interspecies electron transfer (DIET) were examined through thermodynamic analysis based on the energy distribution principle. Types of redox materials could affect the efficiency of DIET via changing the total energy supply of the syntrophic methanogenesis. Decreasing system redox potential could facilitate DIET through increasing the total available energy. The competition between hydrogenotrophic methanogens and DIET methanogens might be the reason for the low proportion of the DIET pathway in the syntrophic methanogenesis. A facilitation mechanism of DIET was proposed based on the energy distribution. Providing sufficient electrons, inhibiting hydrogenotrophic methanogens and adding more competitive redox couples to avoid hydrogen generation might be beneficial for the facilitation of DIET.
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  • 38
    Publication Date: 2022-01-07
    Description: Highlights • NH4NO3, Tris-HCl, and NH4CH3COO are optimal buffers for use in SEC-ICP-MS metalloprotein analyses. • Optimal range of buffer concentration is 50–200 mM in SEC-ICP-MS. • 100 mM concentration reduces both protein column interactions and ICP-MS maintenance. • Dextran-based columns are best suited for the analysis of apo-copper proteins. The correct identification of the metalloproteins present in human tissues and fluids is essential to our understanding of the cellular mechanisms underpinning a host of health disorders. Separation and analysis of biological samples are typically done via size exclusion chromatography hyphenated with inductively coupled plasma-mass spectrometry (SEC-ICP-MS). Although this technique can be extremely effective in identification of potential metalloproteins, the choice of mobile phase may have a marked effect on results, results by adversely affecting metal-protein bonds of the metalloproteins of interest. To assess the choice of mobile phase on SEC-ICP-MS resolution and the resulting metalloproteome pattern, we analysed several different sample types (brain homogenate; Cu/Zn-superoxide dismutase (SOD1); a molecular weight standard mix containing ferritin (Ft), ceruloplasmin (Cp), cytochrome c (CytC), vitamin B12 (B12) and thyroglobulin (Tg) using six different mobile phase conditions (200 mM, pH 7.5 solutions of ammonium salts nitrate, acetate, and sulfate; HEPES, MOPS and Tris-HCl). Our findings suggest that ammonium nitrate, ammonium acetate and Tris-HCl are optimal choices for the mobile phase, with the specific choice being dependent on both the number of samples and method of detection that is hyphenated with separation. Furthermore, we found that MOPS, HEPES and ammonium sulfate mobile phases all caused significant changes to peak resolution, retention time and overall profile shape. MOPS and HEPES, in particular, produced additional Fe peaks that were not detected with any of the other mobile phases that were investigated. As well as this, MOPS and HEPES both caused significant concentration dependent matrix suppression of the internal standard.
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  • 39
    Publication Date: 2022-01-07
    Description: Symbiotic relationships range from parasitic to mutualistic, yet all endosymbionts face similar challenges, including evasion of host immunity. Many symbiotic organisms have evolved similar mechanisms to face these challenges, including manipulation of the host's transforming growth factor-beta (TGFβ) pathway. Here we investigate the TGFβ pathway in scelaractinian corals which are dependent on symbioses with dinoflagellates from the family Symbiodiniaceae. Using the Caribbean coral, Orbicella faveolata, we explore the effects of enhancement and inhibition of the TGFβ pathway on host gene expression. Following transcriptomic analyses, we demonstrated limited effects of pathway manipulation in absence of immune stimulation. However, manipulation of the TGFβ pathway significantly affects the subsequent ability of host corals to mount an immune response. Enhancement of the TGFβ pathway eliminates transcriptomic signatures of host coral immune response, while inhibition of the pathway maintains the response. This is, to our knowledge, the first evidence of an immunomodulatory role for TGFβ in a scelaractinian coral. These findings suggest variation in TGFβ signaling may have implications in the face of increasing disease prevelance. Our results suggest that the TGFβ pathway can modulate tradeoffs between symbiosis and immunity. Further study of links between symbiosis, TGFβ, and immunity is needed to better understand the ecological implications of these findings.
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  • 40
    Publication Date: 2022-01-07
    Description: Highlights • Microplastics act as anthropogenic vectors of trace metals in freshwaters. • Adsorption capacity of microplastics is enhanced by biofilms but is not strong as natural substrates. • Biofilms alter the adsorption kinetics and mechanisms of trace metals onto microplastics. • Microplastics enhance exchange rates of trace metals between water and solid materials. • Anthropogenic substrate is necessary in evaluation of migration and fate of trace metals. Microplastics (MPs) are ubiquitous in freshwater environments, and represent an emerging anthropogenic vector for contaminants, such as trace metals. In this study, virgin expanded polystyrene (PS) particles were placed in a eutrophic urban lake and a reservoir serving as the resource of domestic water for 4 weeks, to develop biofilms on the surface. For comparison, natural adsorbents in the form of suspended particles and surficial sediment were also sampled from these waterbodies. The trace metal adsorption properties of anthropogenic (virgin and biofilm covered microplastics) and natural substrates were investigated and compared via batch adsorption experiments. The adsorption isotherms fitted the Langmuir model, revealed that biofilms could enhance the trace metal adsorption capacity of MPs. However, natural substrates still had a greater adsorption capacity. Biofilms also alter the adsorption kinetics of trace metals onto MPs. The process of adsorption onto virgin MPs was dominated by intraparticle diffusion, whereas film diffusion governed adsorption onto biofilm covered microplastics and natural substrates. The trace metal adsorption of all the substrates was significantly dependent on pH and ionic strength. The adsorption mechanisms were further analyzed by SEM-EDS and FT-IR. The enhancement of adsorption was mainly attributed to complexation with functional groups contained in the biofilms, including carboxyl, amino, and phenyl-OH. Collectively, biofilm development intensifies the role of MPs in the migration and fate of trace metals in freshwater, since it does not give MPs an edge over natural substrates in adsorption.
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  • 41
    Publication Date: 2022-01-07
    Description: Highlights • New insights of CH4 and CO2 hydrates are explored using MD strategy. • The bubble evolution appears to be important over dissociation process. • RDF, MSD, AOP, and diffusion coefficient can be used to examine hydrate stability. • The most stable structure of CH4 and CO2 molecules in the gas hydrate is found. • A promising match is noticed between the MD and literature findings. A comprehensive knowledge and precise estimation of the dynamic, structural, and thermodynamic characteristics of hydrates are needed to assess the stability of gas hydrates. Thermodynamic model and experimental studies can be utilized to compute the physical and dynamic properties of hydrate structures. The use of molecular dynamic (MD) simulation is a well-established approach in gas hydrate studies at the atomic level where the properties of interest are obtained from the numerical solution of Newtonian equations. The present work uses MD simulations by employing the constant temperature-constant pressure (NPT), constant temperature-constant volume (NVT) conditions, and the consistent valence force field (CVFF) to monitor the stability and decomposition of methane and carbon dioxide gas hydrates with different compositions. The effects of temperature and composition on the hydrate stability are investigated. In this study, we also compute the radial distribution function, mean square displacement, diffusion coefficient, lattice parameter, potential energy, dissociation enthalpy as well as the density of methane and carbon dioxide under various thermodynamic and process conditions. The formation of methane and carbon dioxide bubbles is studied to investigate bubble evolution during hydrate dissociation. The sizes of methane and carbon dioxide bubbles are not the same due to different solubility conditions of methane and carbon dioxide in liquid water. In addition, the influences of pressure and temperature on the lattice parameter and density of clathrate hydrates are discussed. The obtained results are consistent with previous theoretical and experimental findings, implying that the methodology followed in this work is reliable. The most stable arrangement of methane and carbon dioxide molecules in the gas hydrate is found. The insights/findings of this study might be useful to further understand detailed transport phenomena (e.g., molecular interactions, gas production rate, carbon dioxide replacement, and carbon dioxide capture) involved in the process of carbon dioxide injection into gas hydrate reservoirs.
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  • 42
    Publication Date: 2022-01-07
    Description: Deep-ocean islands have long been associated with the generation of oceanic eddies in their wakes. However, their interaction with incoming eddies has seldom been considered. This study focuses on the characterization of background and locally generated mesoscale eddies in the Cabo Verde archipelago between 2003 and 2014. Special attention is given to the interaction of incoming eddies with the bathymetry of the islands, along with their impacts on the local generation of eddies. Island-induced wind-shear effects are also considered. In addition, some examples of the biological response to background and locally generated eddies are discussed. This is achieved by combining remote-sensing satellite observations for wind, sea surface height, and chlorophyll-a (Chla) surface concentrations. The results show that the interaction between incoming background eddies and the archipelago is a recurrent phenomenon, which results in eddy deflection, splitting, merging, intensification, and termination (sorted by highest to lowest number of occurrences). Local island-induced disturbances are also significant, mainly due to atmospheric effects. Such processes result in the generation of island-induced eddies and in wind-mediated eddy intensification and confinement, more often observed in the leeward group. Nonetheless, it is strongly suggested that many of the locally generated eddies are a direct product or by-product of the interaction of background eddies with the islands. With respect to the biological realm, a locally generated cyclonic eddy is observed to originate a pronounced phytoplankton bloom in the vicinity of the tallest island. Nonetheless, background eddies generated off the African coast are often associated with enhanced Chla concentrations when they intersect the archipelago. Such observations challenge the idea that local biological productivity in deep oceanic islands is exclusively driven by island-induced mechanisms.
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  • 43
    Publication Date: 2022-01-07
    Description: In an era of electronics, recovering the precious metal such as gold from ever increasing piles of electronic-wastes and metal-ion infested soil has become one of the prime concerns for researchers worldwide. Biological mining is an attractive, economical and non-hazardous to recover gold from the low-grade auriferous ore containing waste or soil. This review represents the recent major biological gold retrieval methods used to bio-mine gold. The biomining methods discussed in this review include, bioleaching, bio-oxidation, bio-precipitation, bio-flotation, bio-flocculation, bio-sorption, bio-reduction, bio-electrometallurgical technologies and bioaccumulation. The mechanism of gold biorecovery by microbes is explained in detail to explore its intracellular mechanistic, which help it withstand high concentrations of gold without causing any fatal consequences. Major challenges and future opportunities associated with each method and how they will dictate the fate of gold bio-metallurgy from metal wastes or metal infested soil bioremediation in the coming future are also discussed. With the help of concurrent advancements in high-throughput technologies, the gold bio-exploratory methods will speed up our ways to ensure maximum gold retrieval out of such low-grade ores containing sources, while keeping the gold mining clean and more sustainable.
    Type: Article , PeerReviewed
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  • 44
    Publication Date: 2022-05-31
    Description: One of the best-known greenhouse gases, CO2, has been increasing in the last decade of about 1.7%. To overcome the well-known global problems related to this gas, researchers of all over the world are working very hard in order to develop any strategies to seriously solve this issue. In this chapter, the authors focus their attention on one of the possible solutions to the problem: bacteria that are CO2 capture cells which have carried out this task since ancient times. In our work we make an excursus on all the biochemical processes of CO2 capture carried out by bacteria, ending with a detailed comparison of the most studied enzymes. One of the alternatives will be to genetically modify the organisms known to date to speed up their conversion process.
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  • 45
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract The effects of Tertiary Alpine metamorphism on pelitic Mesozoic cover rocks have been studied along a cross-section in the central Lepontine Alps in the Nufenen Pass area, Switzerland.Greenschist facies to amphibolite facies conditions are indicated by the formation of the index minerals chloritoid, garnet, staurolite and kyanite in pelitic rocks. Regional metamorphism reached maximum conditions during the interkinematic period between a main Alpine penetrative (D2) and a late Alpine (D3) crenulation type deformation phase or synchronous with the late Alpine deformation. Based on AFM phase relationships four different metamorphic zones can be distinguished: (1) chloritoid zone; (2) staurolite + chlorite zone; (3) staurolite + biotite zone; and, (4) kyanite zone.The isograds that separate these zones can be modelled by univariant reactions in the KFMASH system. The conditions of metamorphism calculated from geological ther-mobarometers for the maximum post-D2 por-phyroblast stage are from North to South: 500° C at 5-6 kbar and 600° C at 7-8 kbar.Detailed thermobarometry of garnet por-phyroblasts with complex textures suggests that maximum temperature was reached later than maximum pressure. Early garnet growth occurred along a prograde P-T-path, post-D2 rims grew with increasing temperature but decreasing pressure, and finally post-D3 garnet formed along a retrograde P-T-path.It may be concluded from the calculated pressure and temperature difference over a short distance (3 km) across the mapped area that the isogradic surfaces of the post-D2 metamorphism are steeply oriented. The data also suggest that isobaric and isothermal surfaces are parallel.Much of the observed metamorphic pattern can be explained as the result of a significant post-D2 differential uplift of the hot Pennine area relative to the Helvetic area along a tectonic contact zone. The closely spaced isograds (isotherms) in the North may then be interpreted as a thermal effect owing to the emplacement of the hot Pennine rocks against the Got-thard massif with its cover. Whereas, in the Pennine metasediments, post-D2 porphyroblast formation can be related to the decompression path which was steep enough for dehydration reactions to proceed. It is also remarkable that late kyanite porphyroblasts probably formed with decreasing pressure.The interpretation given here for the Nufenen Pass area may also apply to the Luk-manier Pass area where similar metamorphic patterns have been reported by Fox (1975). The formation of the ‘Northern Steep Belt’;, as denned by Milnes (1974b), and the associated late Alpine fold zones may, therefore, have significantly modified the metamorphic pattern of the Helvetic-Penninic contact zone.
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  • 46
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
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  • 47
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract Porphyroblast textures in a Karakorum phyllite reveal that porphyroblast growth was syn-tectonic with respect to a cleavage forming deformation. During and after porphyroblast growth it partitions the deformation such that zones of intensified cleavage are developed which wrap around the porphyroblast whilst the porphyroblast and its strain shadow undergo little deformation. Porphyroblast strain shadows comprise quartz, calcite and felspar with little mica, and are probably formed by solution transfer during deformation. Unless the deformation is so strongly partitioned that no deformation of the porphyroblasts and their immediate surrounds occurs, inequidimensional porphyroblasts will rotate. Porphyroblasts undergo some dissolution after they have finished growing.
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  • 48
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract New isotopic (Rb–Sr, U–Pb zircon and Sm–Nd) and petrological data are presented for part of an extensive Proterozoic mobile belt (locally known as the Rayner Complex) in East Antarctica. Much of the belt is the product of Mid-Proterozoic (∼ 1800–2000 Ma) juvenile crustal formation. Melting of this crust at about 1500 Ma ago produced the felsic magmas from which the dominant orthogneisses of this terrain were subsequently derived. Deformation and transitional granulite-amphibolite facies conditions (which peaked at 750 ± 50°C and 7–8 kbar (0.7–0.8 GPa) produced open to tight folding about E–W axes and syn-tectonic granitoids about 960 Ma ago. Subsequent felsic magmatism occurred at about 770 Ma and not, as has been widely advocated, at 500–550 Ma, which appears to have been a time of widespread upper greenschist facies (400–500°C) metamorphism, localized shearing and faulting.Sm-Nd model ages of 1.65–2.18 Ga disprove a previously favoured hypothesis that the Rayner Complex mostly represents reworked Archaean rocks from the neighbouring craton (Napier Complex). Models that involve rehydration of the Napier Complex are no longer required, since the Rayner Complex was its own source of water. Two episodes of Proterozoic crustal growth are identified, the later of which occurred between about 1200 Ma and 1000 Ma, and was relatively minor. Sedimentation took place only shortly before Late Proterozoic orogenesis.The multiphase history of the Rayner Complex has resulted in complex isotopic behaviour. Three temporally discrete episodes of Pb loss from zircon have been identified, the earliest two of which are responses to the c. 960 Ma and 540 Ma tectonothermal events. Fluid leaching was operative during the later event for there is a good correlation between degree of isotopic discordance and secondary mineral growth. Pb loss during the high-grade event was probably governed by the same process or by lattice annealing. Some zircon suites also document recent Pb loss. Most lower concordia intercepts have no direct geological meaning and are explicable as mixed ages produced by incomplete Pb loss during two or more secondary events. Whereas all zircon separates from the orthogneisses produce U–Pb isotopic alignments, zircons from the only analysed paragneiss produce scattered data, in part reflecting a range of provenance. The 960 Ma event was also associated with the growth of a characteristically low U zircon (∼ 300 μg/g) in rocks of inferred high Zr content.There is ubiquitous evidence for the resetting of Rb–Sr total-rock isochrons. Even samples separated by up to 10 km fail to produce igneous crystallization ages. Minor mineralogical changes produced by the 540 Ma upper greenschist-facies metamorphism were sufficient to almost completely reset some Rb–Sr isochrons and to produce open system conditions on outcrop scale, at least in one location.
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  • 49
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract The preserved array of pressures in the eastern Dalradian indicates that considerable syn- to post-metamorphic differential uplift has occurred. This inferred differential uplift suggests that Buchan sillimanite zone rocks originally lay at higher structural levels than presently adjacent cooler kyanite zone rocks to the west. A number of features are believed to coincide with the western margin of the sillimanite zone. These are a maximum in temperature, sharp thermal features, a high strain zone, and a train of metabasites. These features are explained by invoking syn-metamorphic movement between the Buchan sillimanite zone and the kyanite zone to its west, involving some horizontal component of movement. It is suggested that the lateral, now eroded, equivalents of the Buchan area once provided part of the required tectonic thickening for other parts of the Dalradian. Areas surrounding the Buchan area suffered tectonic burial followed by metamorphism during uplift relative to the Buchan area.
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract The Cretaceous-Eocene basic to intermediate marine volcanic rocks of the Mucuchi Formation constitute the Western Cordillera in northern Ecuador. Their chemical features mostly correspond to those of tholeiitic basalts with some calc-alkaline affinities and suggest an oceanic island arc setting. The Macuchi rocks are affected by low-grade, non-deformative metamorphism, characterized by zeolite, prehnite-pumpellyite and lower greenschist facies assemblages. Depth-zonation is suggested by the downward mineral sequence: (i) laumontite+ (pistacitic epidote, pumpellyite + prehnite); (ii) pumpellyite+ prehnite + pistacitic epidote; (iii) actinolite+biotite+ pistacitic epidote + chlorite. This broad zonation and the chemistry of individual minerals point to an interaction between the volcanic rocks and sea-water under a moderate to high thermal gradient (= 75° C/km?). Alteration appears to have been dependent primarily on fluid control (volume, pressure, composition), temperature and reaction kinetics which together partly overshadow the role of load-pressure. Compositional variations of a mineral species at the scale of a contiguous flow or even at the scale of a thin section show that intensity of alteration was spatially uneven depending on rock permeability and consequently, metastable equilibrium commonly exists. However, a progressive approximation to equilibrium as a result of P–T control is shown by the mineralogy. A high fo2 of the fluid phase is evident from the mineral chemistry. The metamorphism of the Macuchi volcanics is similar to the hydrothermal-burial type produced during the development of a volcanic arc where lavas and volcanoclastics accumulated in a shallow marine environment. However, some of its characteristics point to a transition toward systems defined by a higher T/P ratio such as those found in ocean-floor metamorphism.A model is proposed in which the Macuchi volcanics are assigned to an oceanic island arc generated contemporaneously with a marginal basin which has opened as the outcome of progressive north-south attenuation of the continental crust due to mantle diapirism.
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  • 51
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
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    Topics: Geosciences
    Notes: Abstract Several small bodies of metabasite (maximum dimensions of 1000 m x 500 m) are included in the metamorphic rocks of the Nevado-Filabride Complex in the Betic Cordilleras (Almeria Region). The body of 400 m x 100 m, located 200 m due west of the Lubrin village, contains troctolitic gabbro with well-preserved igneous textures and mineral compositions, wholly amphibolitized gabbro, garnet-bearing metagabbro eclogite. Along with the textural and mineral changes, sensible and regular geochemical variations can be observed, where the content of MgO decreases from 24% to 11%, while that of CaO and Na2O increases from 7% to 11% and from 2% to 3%, respectively. In addition, the content of some minor elements such as Sr, Y, Nb, Zr and Sc increases while that of Ni and Cr decreases from troctolitic gabbro to the eclogite. The amphibolitized gabbro shows values scattered around those of the troctolitic gabbro. These geochemical variations are ascribed to inherited differences in the pre-metamorphic protolith, i.e. a fractionated gabbro which varies from olivine-rich to clinopyroxene-rich gabbro. Nevertheless, some metasomatism affected the Lubrin body without changing the main chemical trends, as documented by the significantly different 87Sr/86Sr ratios of each rock-type. This points to a metasomatism which involved the introduction of crustal radiogenic strontium. The petrographical and mineral chemical features are interpreted to be the result of syn-metamorphic fluid circulation possibly combined with deformation by shearing. The igneous texture and mineral chemistry have been retained wherever both fluid circulation and shearing were ineffective. On the contrary, where both events were effective, the formation of eclogite occurred. Later, the entire body underwent a retrogressive amphi-bolitic stage under greenschist facies conditions, which was probably responsible for the formation of the amphibolitized gabbro portion and for the retrogression of the eclogite.
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  • 52
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract Scapolite, wollastonite, calcite, diopside, grossular-andradite garnet and sphene occur in calc-silicate rocks in the granulite terrain of the Arunta Block, central Australia. This assemblage buffers the CO2 activity at a low value, so that any coexisting fluid phase must be H2O rich and CO2 poor (Xco2= 0.2-0.3). In contrast, the H2O activity in the surrounding felsic and mafic granulites was low. Thus fluid activities during granulite facies metamorphism were locally buffered in various rock units and fluid flow appears to have been restricted or fluid may have been absent. Late retrograde rims of garnet and garnet-quartz separate phases formed in the high-grade stage. Formation of these rims would have required either an influx of water-rich fluid or a decrease in pressure. Evidence from the surrounding granulites shows that in one locality, the calc-silicate rocks had undergone late isobaric hydration; in another locality, minor uplift had occurred soon after peak P-T conditions. In both, scapolite had partly broken down to plagioclase-calite. A calc silicate rock from the granulite terrain of Enderby Land, Antarctica, contains scapolite, wollastonite, calcite, diopside, quartz and sphene; this assemblage also indicates low CO2 activities. In this rock, wollastonite has broken down to calcite-quartz, to indicate isobaric cooling without influx of hydrous fluid.
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract Chloritoid-bearing metasedimentary rocks occur in close proximity to blueschists and eclogites in the Tertiary high-pressure metamorphic belt of northern New Caledonia. The typical assemblage of chloritoid-bearing rocks in the epidote zone is quartzchlorite-muscovite-garnet-chloritoid. In the omphacite zone, epidote is an additional member of the chloritoid-bearing assemblage. Paragonite is rare, plagioclase was not detected, and rutile and ilmenite are the Fe-Ti oxide phases. Chloritoid-glaucophane is not a common assemblage. Chloritoid-bearing rocks have relatively low (Ca+K+Na)/Al ratios and the chloritoids are relatively Mg-rich with Mg/ (Mg+Fe) up to about 0.4. A comparison of the mineral assemblages and mineral chemistry with experimental and computed phase equilibria suggest an upper temperature limit near 560° C in the omphacite zone and a minimum temperature limit near 450° C at 10 kbar. An empirical garnet-chlorite Fe-Mg exchange thermometer does not yield consistent results for the higher-grade rocks, suggesting Ts ranging from 390 to 535° C in the omphacite zone and 420–465° C in the epidote zone. The distribution coefficient KD= (Fe/Mg)ctd/(Fe/Mg)chl for chloritoid and chlorite ranges from 3.9 to 6.4, values which are lower than those (=10) from lower greenschist facies rocks, but are near those of upper greenschist facies and albite-epidote amphibolite facies.
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  • 54
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract Considering the minerals cordierite (Cd), sapphirine (Sa), hypersthene (Hy), garnet (Ga), spinel (Sp), sillimanite (Si) and corundum (Co) in the system FeO-MgO-Al2O3-SiO2 (FMAS), the stable invariant points are [Co], [Ga], [Cd] and [Sa]. Constraints imposed by experimental data for the system MAS indicate that under low PH2o conditions the invariant points occur at high temperature (〉 900° C) and intermediate pressure (7-10 kbar). This temperature is higher than that commonly advocated for granulite facies metamorphism. In granulites Fe-Mg exchange geothermometers may yield temperatures of 100–150° C below peak metamorphic conditions and evidence for peak temperatures is best preserved by relict high-temperature assemblages and by Al-rich cores in orthopyroxene. Application of the FMAS grid to some well-documented granulite occurrences introduces important constraints on their P-T histories. Rocks of different bulk compositions, occurring in close proximity in the field, may record distinct segments of their P-T paths. This applies particularly to rocks with evidence for reaction in the form of coronas, symplectites and zoned minerals. Consideration of curved reaction boundaries and XMs isopleths may explain apparently contradictory results for the stability of cordierite obtained from low-temperature experiments and thermochemical calculations on the one hand and hightemperature experimental data on the other.
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  • 55
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract The Bergen-Jotun kindred rocks of this study, the Storådalen Complex (SCX), Svartdalen Gneiss (SG) and Mjølkedøla Purple Gabbro (MPG), have been shown to be a co-magmatic series with calc-alkaline affinities. The analyses of Ba, Nb, Y, and Zr presented here show no variation in these elements between the three rock units and are consistent with the calc-alkaline character of the rocks. The lithophile elements Ba, K, and Sr are enriched relative to MORB and the high field strength elements Nb, Y, and Zr are depleted relative to MORB, Zr especially so.The SCX contains rocks with low (〉30) differentiation indices which are interpreted as plagioclase + pyroxene ± olivine ± amphibole cumulates. The remainder of the SCX, together with the MPG and SG, is regarded as the congealed liquid in equilibrium with these cumulates. The distribution of trace elements between these two components of the SCX can be adequately modelled using a Rayleigh fractionation process, measured ‘liquid’compositions, and calculated bulk distribution coefficients. It is thus concluded that the trace element geochemistry of the rocks of this study is consistent with subduction-related, mantle-derived magmas that fractionate within a continental or mature island arc environment. Subsequent high-grade metamorphism and deformation of Sveconorwegian age have been essentially isochemical.
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract High-pressure granulite-facies gneisses in the NE Ox inlier in NW Ireland have undergone extensive Caledonian retrogression. In the local area of Slishwood, however, reworking was negligible and the gneisses (psammites, semipelites, pelites, metabasites and ultramafites) preserve evidence of P–T changes at high grade which mainly post-date pre-Caledonian polyphase deformation. Temperatures reached 850–900°C (based on garnet-clinopyroxene geothermometry and the presence of mesoperthite) during and after decompression from earlier eclogite-facies conditions (inferred from textural evidence of plagioclase release in sieve-textured augite). Subsequent cooling at high pressure is inferred from the unequivocal replacement of sillimanite by kyanite.A Sm–Nd mineral isochron (gt–cpx–plag–WR) of 605 ± 37 Ma is taken to date a point on the cooling path, and confirms the hitherto suspected pre-Caledonian age of the high-grade metamorphism. Geochemical and Sm–Nd isotopic data indicate that the protoliths were probably late Proterozoic arkosic sediments and tholeiites. Following metamorphism they apparently came to reside near the base of the crust where they slowly cooled. The eventual exhumation of these gneisses is attributed to Caledonian crustal imbrication, followed by rapid isostatic recovery.
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract Sphalerite geobarometry has long been known to give poor results when applied to regional metamorphic terranes. Application of the sphalerite geobarometer to three low-to medium-grade sulphide deposits—the Moke Creek and Waitahuna deposits, Otago, and the Goose Cove deposit, Newfoundland—yields pressures up to 9 kbar, which appear to be too high when compared with other geological data. Textural and mineralogical relationships suggest that the Goose Cove and, possibly, the Moke Creek deposits lacked the required equilibrium assemblage (pyrite + hexagonal pyrrhotite + sphalerite) during peak metamorphic conditions, rendering the geobarometer inapplicable. In addition, all three deposits show evidence of re-equilibration at T 〈 300°C, which has resulted in decreased FeS contents and high apparent pressures. Analyses of sphalerites from very low-grade metachert from South Georgia Island, which contains the assemblage sphalerite + pyrite + monoclinic pyrrhotite + chalcopyrite, confirm that low-temperature equilibration of this assemblage results in approximately 10–11 mol. % FeS in sphalerite. Comparison of these results with published descriptions of other deposits suggests that lack of the appropriate assemblage and retrograde re-equilibration of sphalerite probably account for most anomalously high-pressure estimates. Erratic compositions of sphalerites containing chalcopyrite inclusions may result from replacement of high-temperature intermediate solid-solution by chalcopyrite during cooling. Strain may enhance retrograde re-equilibration of sphalerite by grain-size reduction or dislocation-assisted diffusion and/or nucleation. Re-evaluation of the data from Moke Creek suggests that the sulphides experienced pervasive greenschist facies re-equilibration at pressures of about 4.5 kbar, with late stage mobilization at about 2.8 kbar, and thus sphalerite compositions are not likely to reflect blueschist facies conditions. Pressure estimates based on sphalerite geobarometry should take into account at what stage in the history of a metamorphic terrane the sphalerite composition equilibrated.
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract The sedimentary and igneous rocks comprising the lower Proterozoic Olary Block, South Australia, were deformed and metamorphosed during the mid-Proterozoic ‘Olarian’Orogeny. The area is divided into three zones on the basis of assemblages in metapelitic rocks, higher grade conditions occurring in the south-east. Mineral assemblages developed during peak metamorphism, which accompanied recumbent folding, include andalusite in Zones I and II and sillimanite in Zone III. Upright folding and overprinting of mineral assemblages occurred during further compression, the new mineral assemblages including kyanite in Zone II and kyanite and sillimanite in Zone III. The timing relationships of the aluminosilicate polymorphs, together with the peak metamorphic and overprinting parageneses, imply an anticlockwise P–T path for the ‘Olarian’Orogeny, pressure increasing with cooling from the metamorphic peak.
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    Topics: Geosciences
    Notes: Abstract Sodic amphiboles are common in Franciscan type II and type III metabasites from Cazadero, California. They occur as (1) vein-fillings, (2) overgrowths on relict augites, (3) discrete tiny crystals in the groundmass, and (4) composite crystals with metamorphic Ca–Na pyroxenes in low-grade rocks. They become coarse-grained and show strong preferred orientation in schistose high-grade rocks. In the lowest grade, only riebeckite to crossite appears; with increasing grade, sodic amphibole becomes, first, enriched in glaucophane component, later coexists with actinolite, and finally, at even higher grade, becomes winchite. Actinolite first appears in foliated blueschists of the upper pumpellyite zone. It occurs (1) interlayered on a millimetre scale with glaucophane prisms and (2) as segments of composite amphibole crystals. Actinolite is considered to be in equilibrium with other high-pressure phases on the basis of its restricted occurrence in higher grade rocks, textural and compositional characteristics, and Fe/Mg distribution coefficient between actinolite and chlorite. Detailed analyses delineate a compositional gap for coexisting sodic and calcic amphiboles. At the highest grade, winchite appears at the expense of the actinolite–glaucophane pair.Compositional characteristics of Franciscan amphiboles from Ward Creek are compared with those of other high P/T facies series. The amphibole trend in terms of major components is very sensitive to the metamorphic field gradient. Na-amphibole appears at lower grade than actinolite along the higher P/T facies series (e.g. Franciscan and New Caledonia), whereas reverse relations occur in the lower P/T facies series (e.g. Sanbagawa and New Zealand). Available data also indicate that at low-temperature conditions, such as those of the blueschist and pumpellyite–actinolite facies, large compositional gaps exist between Ca- and Na-amphiboles, and between actinolite and hornblende, whereas at higher temperatures such as in the epidote–amphibolite, greenschist and eclogite facies, the gaps become very restricted.Common occurrence of both sodic and calcic amphiboles and Ca–Na pyroxene together with albite + quartz in the Ward Creek metabasites and their compositional trends are characteristic of the jadeite–glaucophane type facies series. In New Caledonia blueschists, Ca–Na pyroxenes are also common; Na-amphiboles do not appear alone at low grade in metabasites, instead, Na-amphiboles coexist with Ca-amphiboles throughout the progressive sequence. However, for metabasites of the intermediate pressure facies series, such as those of the Sanbagawa belt, Japan and South Island, New Zealand, Ca–Na pyroxene and glaucophane are not common; sodic amphiboles are restricted to crossite and riebeckite in composition and clinopyroxenes to acmite and sodic augite, and occur only in Fe2O3-rich metabasites.The glaucophane component of Na-amphibole systematically decreases from Ward Creek, New Caledonia, through Sanbagawa to New Zealand. This relation is consistent with estimated pressure decrease employing the geobarometer of Maruyama et al. (1986). Similarly, the decrease in tschermakite content and increase in NaM4 of Ca-amphiboles from New Zealand, through Sanbagawa to New Caledonia is consistent with the geobarometry of Brown (1977b). Therefore, the difference in compositional trends of amphiboles can be used as a guide for P–T detail within the metamorphic facies series.
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  • 62
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract Contact metamorphism adjacent to a porphyritic quartz-monzodiorite at Kentucky, New South Wales, Australia has produced hornfelses in porphyritic leucogranite at a peak temperature of about 650–700° C and a maximum confining pressure of about 2 kbar (200 MPa). A gradation appears to exist from normal slightly peraluminous to modified strongly peraluminous metagranite hornfelses, which have also been enriched in sulphur. The strongly peraluminous hornfelses, containing cordierite, andalusite, sillimanite, biotite, pyrite and pyrrhotite, retain residual porphyritic igneous microstructures. These rocks appear to have been formed by leaching of base cations, during and possibly just before the contact metamorphism. Folia of fibrous sillimanite anastomose between lenticular grains of quartz and feldspar and truncate igneous zoning in plagioclase grains, suggesting that cation leaching and solution transfer occurred during growth of the sillimanite. Fibrous sillimanite also grew in grain boundaries of polygonal aggregates formed by the contact metamorphism. Therefore, at least some of the cation leaching appears to have occurred at the highest metamorphic grade. Metasandstones that are locally strongly peraluminous adjacent to the monzodiorite stock also, have probably undergone similar leaching.
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  • 63
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
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    Topics: Geosciences
    Notes: Abstract The Paikon Series is considered to be a volcanic arc sequence with a mainly neritic sedimentary sequence and bimodal tholeiitic volcanism of early Mesozoic age. The metamorphic assemblages are syn- to post-kinematic with respect to a pre-Tithonian tectonic phase and range from the lawsonite-chlorite-albite facies through transitional Na-amphibole-greenschist facies to the chlorite sub-zone of the greenschist facies. The metamorphic imprint of the Paikon Series corresponds to a temperature range from less than 330° C to ± 450° C under a total pressure from 3 kbar to 6–7 kbar. The overprinting of these facies on an earlier blueschist assemblage, related either to a subduction zone or to a tectonic overpressure caused by thrusting, is suspected.
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  • 64
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract Textural evolution and compositional variation of clinopyroxenes in Ward Creek metabasites are described. Pyroxenes change, with increasing grade, from finegrained aggregates through fan-shaped medium-grained prisms to blocky coarse crystals. Characteristic features of metamorphic pyroxenes include: (1) the occurrence of coexisting pyroxene pairs, the compositions of which are used to delineate compositional gaps; (2) the existence of large compositional variations of pyroxenes, within a single specimen, which record a considerable span of P and/or T for crystallization; and, (3) the development of compositional trends in single specimens and in three metamorphic zones which are progressive in nature.The first formed clinopyroxene (Jd20Aug65Ac15) in the lower lawsonite zone mimics the composition of relict igneous augite. It changes continuously, with increasing grade, at nearly constant low XJd content towards acmite. At a composition around Jd20Aug30Ac50, the trend turns towards jadeite and intersects a solvus to form two coexisting clinopyroxenes in the middle lawsonite zone. At higher grade, the compositional gap becomes restricted towards the jadeite-omphacite join and clinopyroxene increases in XJd toward jadeite. A reversed compositional trend occurs at higher grade; clinopyroxenes decrease in jadeite component at nearly constant Aug/Ac ratio of 50/50 and finally become omphacite in the uppermost pumpellyite and epidote zones. The Na–Ca pyroxenes, close to the binary join Jd–Ac, occur in the lawsonite- and pumpellyite-zones, ranging from XJd= 1.0–0.30 together with Ab and Qz. The ubiquitous occurrence of aragonite at temperature estimates of 170–240° C by Taylor & Coleman (1968) for these zones does not support the low-temperature extrapolation of the Jd–Ab–Qz curve by Holland (1980).The estimated metamorphic field gradient indicates an inflection point at 7 kbar, 200° C. Below this, blueschist facies metamorphism proceeded under dominant pressure-increase from 4 to 7 kbar at nearly constant temperature, about 150–200° C, whereas at higher grade recrystallization, above the inflection point, the metamorphic temperature increased from 200 to 350° C at nearly constant pressure, about 7–8 kbar. Such an inflection point suggests the depth of underplating of either seamounts or accretionary packages in a subduction zone.
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  • 65
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    Topics: Geosciences
    Notes: Abstract Sapphirine-bearing rocks occur in three conformable, metre-size lenses in intrusive quartzo-feldspathic orthogneisses in the Curaçà valley of the Archaean Caraiba complex of Brazil. In the lenses there are six different sapphirine-bearing rock types, which have the following phases (each containing phlogopite in addition):A: Sapphirine, orthopyroxene;B: Sapphirine, cordierite, orthopyroxene, spinel;C: Sapphirine, cordierite;D: Sapphirine, cordierite, orthopyroxene, quartz;E: Sapphirine, cordierite, orthopyroxene, sillimanite, quartz;F: Sapphirine, cordierite, K-feldspar, quartz.Neither sapphirine and quartz nor orthopyroxene and sillimanite have been found in contact, however. During mylonitization, introduction of silica into the three quartz-free rocks (which represent relict protolith material) gave rise to the three cordierite and quartz-bearing rocks. Stable parageneses in the more magnesian rocks were sapphirine–orthopyroxene and sapphirine–cordierite. In more iron-rich rocks, sapphirine–cordierite, sapphirine-cordierite–sillimanite, cordierite–sillimanite, sapphirine–cordierite–spinel–magnetite and quartz–cordierite–orthopyroxene were stable. The iron oxide content in sapphirine of the six rocks increases from an average of 2.0 to 10.5 wt % (total Fe as FeO) in the order: C,F–A,D–B,E. With increase in Fe there is an increase in recalculated Fe2O3 in sapphirine.The four rock types associated with the sapphirine-bearing lenses are:I: Orthopyroxene, cordierite, biotite, quartz, feldspar tonalitic to grandioritic gneiss;II: Biotite, quartz, feldspar gneiss;III: Orthopyroxene, clinopyroxene, hornblende, plagioclase meta-norite;IV: Biotite, orthopyroxene, quartz, feldspar, garnet, cordierite, sillimanite granulite gneiss.The stable parageneses in type IV are orthopyroxene–cordierite–quartz, garnet–sillimanite–quartz and garnet–cordierite–sillimanite.Geothermobarometry suggests that the associated host rocks equilibrated at 720–750°C and 5.5–6.5 kbar. Petrogenetic grids for the FMASH and FMAFSH (FeO–MgO–Al2O3–Fe2O3–SiO2–H2O) model systems indicate that sapphirine-bearing assemblages without garnet were stabilized by a high Fe3+ content and a high XMg= (Mg/ (Mg+Fe2+)) under these P–T conditions.
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  • 66
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract Chloritoid–hornblende occurs in quartz–muscovite pelitic schist derived from sediment in a volcaniclastic sequence of the Grenville Supergroup and from reworked sedimentary and regolithic material above the unconformity at the base of the Flinton Group. Comparison of these samples with other pelitic rocks on triangular composition diagrams and in the ACNF and ACFM tetrahedra indicates that the presence of hornblende cannot be explained by unusually high CaO content. The rare assemblage is attributed to a combination of relatively low Al2O3 and high K2O with high CaO/(CaO+Na2O) and FeO/(FeO+MgO).On two qualitative reaction grids derived from AFM diagrams projected through CaO and plagioclase, respectively, the P–T stability field of chloritoid–hornblende overlaps the first appearance of staurolite–biotite in normal pelitic rocks in the kyanite field. Staurolite–hornblende overlaps chloritoid–hornblende and extends to the higher temperatures and pressures of the kyanite–hornblende field.The phase relations in these rocks provide a link between the conventional hornblende-absent grids for pelitic rocks and those for K2O-poor (muscovite-absent) pelitic and mafic amphibolitic rocks.
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
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    Topics: Geosciences
    Notes: Abstract The effect of ductile deformation (dislocation creep) on the kinetics of the aragonite-calcite transformation has been studied at 1 atm (330° C and 360° C) and 900-1500 MPa (500° C) using undeformed and either previously or simultaneously deformed samples (500° C and a strain rate of 10-6 s). Deformation enhances the rate of the transformation of calcite to aragonite, but decreases the rate of transformation of aragonite to calcite. The difference results from a dependence of transformation rate on grain size, coupled with a difference in the accommodation mechanisms, climb versus recry-stallization, of these minerals during dislocation creep. Dislocation climb is relatively easy in calcite and thus plastic strain results in high dislocation densities without significant grain size reduction. The rate of transformation to aragonite is enhanced primarily because of the increase in nucleation sites at dislocations and subgrain boundaries. In aragonite, on the other hand, dislocation climb is difficult and thus plastic strain produces extensive dynamic recry-stallization resulting in a substantial grain size reduction. The transformation of aragonite is inhibited because the increase in calcite nucleation sites at dislocations and/or new grain boundaries is more than offset by the inability of calcite to grow across high angle grain boundaries. Thus the net effect of ductile deformation by dislocation creep on the kinetics of polymorphic phase transformations depends on the details of the accommodation mechanism.
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    Journal of metamorphic geology 5 (1987), S. 0 
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  • 69
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract Cordierite-anthophyllite rocks and related cordierite-rich, talc-rich and chlorite-rich rocks occur in the Rosebud Syncline, north-west Queensland, Australia, as part of a Proterozoic metasedimentary sequence. Field relations and rock compositions attest the sedimentary origin of these rather unusual metamorphic rocks. Their chemical composition is comparable to that of unmetamorphosed, alkali- and Ca-poor pelites, which are associated with some evaporite deposits.Other occurrences of cordierite-anthophyllite rocks have commonly been interpreted as metamorphosed chloritic alteration products derived from mafic or felsic volcanics. A comparative chemical study, using analyses of cordierite-anthophyllite rocks from such alteration zones and analyses of unmetamorphosed magnesian pelites, demonstrates the general chemical similarity between these two rock groups of entirely different origin. However, distinct differences in major element relations help to distinguish these two genetic groups. Particularly useful are Al2O3–FeO–MgO plots, in which evaporitic pelites occupy the Fe-poor side.The highly magnesian metamorphic rocks from the Rosebud Syncline fall entirely into the compositional field of evaporitic clays and shales. Furthermore, analyses of relatively immobile trace elements give supporting evidence for the sedimentary origin of these cordierite-anthophyllite rocks. The correlation with trace element ranges of clays and shales is very good. However, the correlation with trace element ranges of mafic and felsic volcanics is poor, and major discrepancies occur with Cr, Ni, Co, Nb, Sc, Th and Ti.Thus, the magnesian metamorphics of the Rosebud Syncline appear to be derived from evaporitic clays rich in magnesian clay minerals, such as palygorskite, sepiolite, chlorite or corrensite. The complete metamorphic rock assemblage of interlayered calcareous, aluminous and magnesian rocks is interpreted as a metamorphosed carbonate-evaporite-pelite sequence.
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  • 71
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    Journal of metamorphic geology 5 (1987), S. 0 
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  • 72
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    Journal of metamorphic geology 5 (1987), S. 0 
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  • 73
    ISSN: 1525-1314
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    Topics: Geosciences
    Notes: Abstract A suite of granulites including a meta-ironstone, pyroxenites, and spinel-lherzolites from East Tonagh Island, Enderby Land, Antarctica, preserve exsolution-recry-stallization features consistent with a shared metamorphic evolution that involves marked cooling from initial metamorphic temperatures of nearly 1000°C. Reintegrated pre-exsolution and pre-reaction grain compositions in the meta-ironstone indicate the former coexistence of metamorphic pigeonite (Wo12En38Fs50) and ferroaugite (Wo35En31Fs34) at temperatures in excess of 980°C for pressures of 7 kbar (0.7 GPa) using pyroxene quadrilateral thermometry (Lindsley, 1983). Intra-grain lamellae relationships indicate the exsolution of a second pigeonite (Wo12En35Fs53) from the ferroaugite at temperatures in the range 930–970°C, prior to the c. 720–600°C exsolution of orthopyroxene and clinopyroxene (100) lamellae and later partial recrystallization at similar temperatures. Although pyroxenitic and iherzolitic granulites preserve a much less complete history, reintegrated porphyroclast compositions in these yield temperature estimates which approach those inferred from the metaironstone. Pyroxene thermometry based on neoblast compositions suggests that recrystallization post-dating a late, low intensity, deformation phase (D3) occurred at temperatures greater than 600°C. These results are consistent with the independent evidence obtained from studies of metapelitic and felsic rock types for very high temperature metamorphism throughout the Napier Complex followed by near-isobaric cooling and later deformation under lower-grade granulite facies conditions. Comparison with similar pyroxene data from Fyfe Hills (Sandiford & Powell, 1986) demonstrates further the regional significance of these high temperatures, and implies broadly isothermal metamorphic conditions over a large area (∼ 5000 km2) and thickness (6–9 km) of lower crust at c. 3070 Ma.
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  • 74
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract A detailed field and petrological study of rocks from nappes cut by the Valle dell'Orco (Italian Western Alps), in particular the Sesia–Lanzo composite unit, has revealed geological and metamorphic histories which started in pre-alpine times and lasted up to the alpine subduction-collisional processes. During these processes the nappes sustained an early high P–low T stage and a later low P greenschist facies stage, but followed partly distinctive P–T–time trajectories. This paper discusses the kinematic evolution and the thermal history of the alpine belt from the early subduction/underthrust to the later exhumation stage. The metamorphic crystallization is often governed by incomplete and/or local equilibrium, and the pervasive syn-metamorphic deformation and the composition of the syn-metamorphic fluid phase (if present) have exerted an effective local control on reaction kinetics.
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  • 75
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract Optical and X-ray studies of carbonaceous material in the Tono contact metamorphic aureole, Kitakami Mountains, northeast Japan, have revealed that metamorphic graphitization proceeded through two discontinuous changes: first, optically anisotropic domains develop within the coaly phytoclast, forming transitional material, and then, ordered graphite crystallizes by the decomposition of pre-existing carbonaceous materials. Coaly material disappears in the uppermost chlorite zone. Transitional material appears in the middle of the lower chlorite zone. Graphite appears in the upper chlorite zone and its modal abundance increases across the andalusite iso-grad to the cordierite isograd where all the carbonaceous materials have converted to graphite. The apparently continuous variation in the crystallographic parameters of the bulk carbonaceous material during graphitization is largely due to variation in the modal proportions of three types of carbonaceous materials. The temperature of graphitization in the present area is at least 100°C higher than the temperature in the Sanbagawa and New Caledonia high-pressure metamorphic terrains, probably due to the slow reaction rate of metamorphic graphitization and to the short duration of contact metamorphism.
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  • 76
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract Dissolution of quartz and the recryst-allization and re-equilibration of phyllosilicates produce the dark anastomosing seams that dominate microstructures of tectonic melange which occur in a low-grade, imbricated and multiply deformed, mid-Palaeozoic, intracra-tonic fiysch sequence in northeastern Australia. Seams are composed of very closely spaced or coalesced cleavage lamellae, which are very thin layers of extremely fine-grained phyllosilicates. Cleavage seams enclose lenses of silt-stone or greywacke, which formerly occurred in continuous sedimentary layers, indicating extremely heterogeneous and disruptive deformation. Microphacoids enclosed by cleavage seams have subtle shape asymmetries analogous to those of porphyroclasts. Phyllosilicate-preferred orientations within microphacoids commonly lie at a low angle to enclosing seams, and asymmetric relationships occur within seams. The shape and fabric asymmetries appear to be constant, and are regarded as analgous to S and C planes. The number and extent of seams, the amount of dissolution they indicate, and the efficiency of deformation partitioning imply some enhancement of chemical activity and substantial silica loss from the system. This, in turn, suggests the passage of large amount of silica-undersaturated fluid, and melanges may be zones of high fluid flow. However, the microstructures and the disruptive nature of the fabrics may also reflect the influence of high bulk shear strains and suggest some relationship between the shearing component of deformation and the development of cleavages and foliations.
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  • 77
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    Journal of metamorphic geology 5 (1987), S. 0 
    ISSN: 1525-1314
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    Topics: Geosciences
    Notes: Abstract In the Bois de Cené area, blueschist facies rocks, characterized by glaucophane and/ or chloritoid, provide evidence for a suture zone in the Variscan. This terrain is considered to be the eastern equivalent of the Ile de Groix high-pressure metamorphic terrain. Petrological study of the two characteristic types of rocks found in the area shows that the primary high-pressure paragenesis was modified during a retrogression which followed substantial decompression, probably at constant or decreasing temperature. The simplest interpretation is that this retrogression followed tectonic emplacement within a nappe pile.
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    Topics: Geosciences
    Notes: Abstract In the Fleur de Lys Supergroup, western Newfoundland, inclusion trails in garnet and albite porphyroblasts indicate that porphyroblasts overgrew a crenulation foliation, without rotation, probably during the deformation event that produced the crenulations. Further deformation of the matrix resulted in strong re-orientation and retrograde metamorphism of the matrix foliation, which is consequently highly oblique to the crenulation foliation preserved in the porphyroblasts. The resulting matrix foliation locally preserves relics of the early crenulations, and also has itself been crenulated later in places. Thus the porphyroblasts grew before the later stages of deformation, rather than during the final stage, as had been suggested previously. The new interpretation is consistent with available 40Ar/39Ar cooling ages which indicate a late Ordovician-early Silurian metamorphic peak, rather than the Devonian peak suggested by previous workers. The inclusion patterns and microprobe data indicate normal outward growth of garnet porphyroblasts from a central nucleus, rather than as a series of veins as proposed by de Wit (1976a, b). However, the observations presented here support growth of porphyroblasts without rotation, which is implied by the de Wit model.
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract In foliated K-feldspar-sillimanite metapelites, fibrous sillimanite is commonly concentrated in folia that anastomose between lenticular pods of coarser-grained aggregates rich in quartz, feldspar and biotite, with or without garnet, cordierite and residual andalusite. Many of the folia appear to be limbs of crenulation microfolds. The sillimanite concentrations may be due largely to the ability of fibrous sillimanite aggregates to undergo strong non-coaxial deformation by grain-boundary sliding (‘fibre sliding’;) without appreciable build-up of dislocations, whereas other minerals are unstable in these zones and so concentrate in lower-strain interfolial zones. Initiation, and especially concentration of the sillimanite in folia, may be assisted by fluid flow and local base-cation leaching, whereby minerals unstable in zones of strong non-coaxial strain are dissolved and removed from these zones.
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    Journal of metamorphic geology 5 (1987), S. 0 
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    Topics: Geosciences
    Notes: Abstract Comparison of the stability relations of Fe-piemontite, Pm17Ps17Cz66 (Ca2Al2Mn0.5 Fe0.5Si3O12(OH)), with similar experimentally determined results on Pm33Cz67 suggests that, at moderate fo2, addition of Fe to piemontite raises its thermal stability and slightly decreases its sensitivity to oxygen fugacity. Reversal study of the reaction: Fe-piemontite + quartz = garnet (Gr33Sp27And40) + anorthite + fluid at Pfluid= 2 kbar in cold-seal apparatus using solid oxygen buffers was completed. The data indicated breakdown of Pm17Ps17Cz66 at 645°± 10° C along the Cu2O–CuO buffer, 477°± 10° C along the Cu–Cu2O buffer, and 365°± 10° C for the hematite-magnetite buffer. Mn-free clinozoisite and epidote have been shown to be stable to much higher temperatures than piemontite at moderate fo2 (〈 Cu–Cu2O). At very high fo2, however, the presence of Mn+3 in a distorted octahedral site may permit persistence of piemontite to higher temperatures than Mn-poor epidote minerals.The compositional range of natural Fe–Mn–Al piemontites supports these results. Cation partitioning from piemontite-bearing parageneses also indicates crystallization at high fo2, but application of the cited results should be made with caution. Synthetic phases were too fine-grained for optical or microprobe analysis, and reaction was often incomplete. The assumption that all Fe + Mn was contained in piemontite and garnet, respectively, in the low- and high-temperature assemblages is supported by the cell dimensions for these synthetic minerals, which are close to predicted values. The reaction is pseudo-univariant, as solid solution in garnet and piemontite would be fo2-dependent in a more complex chemical system. Although bulk rock and fluid compositions may also have a marked effect on the stability of natural epidote–piemontite, fo2 is the major control on Fe : Mn : Al in epidote minerals.
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    Topics: Geosciences
    Notes: Abstract Pelitic assemblages from all major Witwatersrand gold fields record metamorphic conditions of the greenschist facies, with minimal regional grade changes over at least 200 km strike length. Diagnostic metamorphic assemblages are less common in the volumetrically dominant quartzites, the actively-exploited auriferous conglomerates and some of the regionally persistent metapelitic horizons. Bulk rock composition has been a major control on assemblage development.Key metapelitic assemblages include pyrophyllite, chloritoid, chlorite and muscovite in each gold field, with less common metamorphic biotite. Accessory minerals are pyrite, tourmaline, rutile and zircon. The abundance of chloritoid and pyrophyllite in thin shaly units, together with their minor, but widespread, distribution in quartzites and conglomerates, indicate that metamorphic temperatures reached 350°C ± 50°C in all the gold fields. Pressures are less-well constrained, 1–2 kbar being inferred. Outside the gold fields, higher grades are indicated by andalusite and kyanite near granitoid domes and later intrusions.The temperatures during peak metamorphism and the abundance of pyrite provide ideal conditions to (re)mobilize gold and may explain its secondary textural features.
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    Topics: Geosciences
    Notes: Abstract Corona textures, which developed in alternating layers in rocks in a supracrustal belt at Errabiddy, Western Australia, involved:(a) The production of staurolite, cordierite and quartz or sapphirine between Kyanite and/or sillimanite and gedrite; and(b) The production of cordierite between garnet and gedrite.These textures are inconsistent with development along the same pressure–temperature path in the system FeO–MgO–Al2O3–SiO2–H2O, but can be accounted for if CaO, mainly in garnet, is taken into account. The sapphirine-bearing kyanite–gedrite textures are explained by lower a(SiO2) during their development. The assemblages indicate a consistent pressure–temperature (P–T) trajectory involving substantial uplift with only a slight decrease in temperature. The history of these rocks includes reheating of originally high-grade rocks that had cooled to a stable conductive geotherm, followed by substantial, essentially isothermal uplift. The tectonic environment for this was presumably the one responsible for emplacement of the high-grade terrain in the upper crust.
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    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: The availability of data in digital formats, the rapid evolution of computer systems and the increased demands for cartographic databases are causing photogrammetrists to consider ways of integrating photogrammetric, remote sensing and database technologies. Examples are presented involving the use of aerial photographs and satellite images in combination with geographical information systems and image processing techniques to assess soil erosion, growth of aquatic vegetation and to enhance satellite images for the compilation or revision of map products.
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
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    Topics: Architecture, Civil Engineering, Surveying
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  • 87
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
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  • 88
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: A new lightweight vertical camera rig which can be clamped to the front legs of the front seat of a light aircraft is described. In one version, a fixed transparent fairing is attached to the door, whereas in the second version the fairing is attached to the camera rig itself which can then be extended and retracted in flight. This rig has received C.A.A. (Civil Aviation Authority) Approval.
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  • 89
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: SPOT-1, launched on 22nd February, 1986, has provided the first opportunity to produce topographic maps from space on an operational basis. The use of SPOT imagery can be justified because of reduced costs and reduced lead times for map production. However SPOT imagery cannot be handled in the same way as conventional photography and it requires new procedures to be adopted, The two main reasons for this are the large area covered by each image and the dynamic form of sensing. The procedures discussed in this paper have been implemented in a working system for map compilation.
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  • 90
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
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  • 91
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: In 1904, Dr. H. G. Fourcade compiled the first recorded topographic map made using analytical stereophotogrammetric methods. This paper describes how, in 1985, the stereophotography was repeated in very close proximity to Fourcade's original camera base using a modern metric camera. A new topographic map was compiled by computer graphics from stereoscopic observations made on a modern stereocomparator. A direct comparison of the two sets of interpolated contour lines demonstrates that Fourcade produced a highly accurate map covering part of Devil's Peak which is adjacent to Table Mountain near the city of Cape Town.
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  • 92
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: The effect on accuracy resulting from some changes to the conventional least squares matching method is investigated. Parallaxes computed automatically with matching methods have been compared with manual measurements made in a stereocomparator. Examples have been taken from both large and small scale aerial photographs and from close range images. Different linear geometric and radiometric parameters have been used as additional unknowns. The use of data snooping in digital matching with the least squares matching method has also been investigated. The results show that the introduction of additional affine parameters has a positive effect on the accuracy when the window size is larger than 30 × 30 pixels. The use of the data snooping technique is promising. The best precision obtained was between 10 pm and 15 μm, expressed as radial root mean square deviation, corresponding to approximately half a pixel. Gross error detection is possible to a large extent with photographs of good image quality.
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  • 93
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
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  • 94
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: The author continues the discussion of a Norwegian project to develop a stereoscopic instrument which will reduce the cost of analytical photogrammetry. Parts I and II of the project were presented at the 1984 Thompson Symposium; the objective at that stage was to build an image space plotter. This paper covers Part III of the project and the extended objective to develop an inexpensive analytical plotter which links with a modern microcomputer.
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  • 95
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Previous assessments of the accuracy of parallax bar heighting were handicapped by small sample sizes. Numerical simulation was avoided due to the difficulty of obtaining co-ordinates for the conjugate principal points. This problem has been overcome, however, and all required photograph coordinates have been rigorously computed following the generation of fictitious data for ground points and exposure stations. The parallax bar heighting process has additionally been simulated in order to investigate both external factors, such as image errors, tilts and ground relief, and also influences intrinsic in the heighting process, for example estimation of flying height, baselining, control configuration and error surface model.
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
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    Topics: Architecture, Civil Engineering, Surveying
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
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    Topics: Architecture, Civil Engineering, Surveying
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    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 12 (1987), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Book reviewed in this aticle:AERIAL PHOTO-INTERPRETATION IN TERRAIN ANALYSIS AND GEOMORPHOLOGIC MAPPING. By R. A. van Zuidam.REMOTE SENSING: METHODS AND APPLICATIONS. By R. M. Hord.FRENCH-ENGLISH GLOSSARY ON SPOT, REMOTE SENSING AND THEIR APPLICATIONS. By S. T. Dyson.REMOTE SENSING. PRINCIPLES AND INTERPRETATION. Second Edition. By F. F. Sabins.APPLIED REMOTE SENSING. By C. P. Lo.HISTORY OF CARTOGRAPHY. By L. Bagrow.REMOTE SENSING YEARBOOK 1987. Edited b A. P. Cracknell and L. W. B. Hayes.WINGS OVER ICE. By P. G. Mott.MANUAL OF AERIAL PHOTOGRAPHY. By R. W. Graham and R. E. Read.
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