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  • AGU (American Geophysical Union)  (3)
  • American Association of Petroleum Geologists (AAPG)  (1)
  • National Academy of Sciences  (1)
  • Nature Publishing Group (NPG)  (1)
  • 1
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    Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch (2012)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2012-08-04
    Description: The warmest global climates of the past 65 million years occurred during the early Eocene epoch (about 55 to 48 million years ago), when the Equator-to-pole temperature gradients were much smaller than today and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume. Recently the early Eocene has received considerable interest because it may provide insight into the response of Earth's climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future as a consequence of unabated anthropogenic carbon emissions. Climatic conditions of the early Eocene 'greenhouse world', however, are poorly constrained in critical regions, particularly Antarctica. Here we present a well-dated record of early Eocene climate on Antarctica from an ocean sediment core recovered off the Wilkes Land coast of East Antarctica. The information from biotic climate proxies (pollen and spores) and independent organic geochemical climate proxies (indices based on branched tetraether lipids) yields quantitative, seasonal temperature reconstructions for the early Eocene greenhouse world on Antarctica. We show that the climate in lowland settings along the Wilkes Land coast (at a palaeolatitude of about 70 degrees south) supported the growth of highly diverse, near-tropical forests characterized by mesothermal to megathermal floral elements including palms and Bombacoideae. Notably, winters were extremely mild (warmer than 10 degrees C) and essentially frost-free despite polar darkness, which provides a critical new constraint for the validation of climate models and for understanding the response of high-latitude terrestrial ecosystems to increased carbon dioxide forcing.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pross, Jorg -- Contreras, Lineth -- Bijl, Peter K -- Greenwood, David R -- Bohaty, Steven M -- Schouten, Stefan -- Bendle, James A -- Rohl, Ursula -- Tauxe, Lisa -- Raine, J Ian -- Huck, Claire E -- van de Flierdt, Tina -- Jamieson, Stewart S R -- Stickley, Catherine E -- van de Schootbrugge, Bas -- Escutia, Carlota -- Brinkhuis, Henk -- Integrated Ocean Drilling Program Expedition 318 Scientists -- England -- Nature. 2012 Aug 2;488(7409):73-7. doi: 10.1038/nature11300.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Paleoenvironmental Dynamics Group, Institute of Geosciences, Goethe University Frankfurt, Altenhoferallee 1, 60438 Frankfurt, Germany. joerg.pross@em.uni-frankfurt.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22859204" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antarctic Regions ; Atmosphere/chemistry ; Carbon Dioxide/analysis ; Cell Respiration ; Ecosystem ; Geologic Sediments/chemistry ; Greenhouse Effect/*history ; History, Ancient ; Human Activities ; Lipids/analysis ; Models, Theoretical ; Photosynthesis ; Pollen ; Reproducibility of Results ; Seasons ; Spores/isolation & purification ; *Temperature ; Trees/growth & development ; *Tropical Climate
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Eocene cooling linked to early flow across the Tasmanian Gateway (2013)
    National Academy of Sciences
    Details
    Publication Date: 2013-05-29
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 3
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    Linking process, dimension, texture, and geochemistry in dolomite geobodies: A case study from Wadi Mistal (northern Oman) (2013)
    American Association of Petroleum Geologists (AAPG)
    Details
    Publication Date: 2013-07-03
    Description: Understanding the distribution and geometry of reservoir geobodies is crucial for net-to-gross estimates and to model subsurface flow. This article focuses on the process of dolomitization and resulting geometry of diagenetic geobodies in an outcrop of Jurassic host rocks from northern Oman. Field and petrographic data show that a first phase of stratabound dolomite is crosscut by a second phase of fault-related dolomite. The stratabound dolomite geobodies are laterally continuous for at least several hundreds of meters (~1000 ft) and probably regionally and are one-half meter (1.6 ft) thick. Based on petrography and geochemistry, a process of seepage reflux of mesosaline or hypersaline fluids during the early stages of burial diagenesis is proposed for the formation of the stratabound dolomite. In contrast, the fault-related dolomite geobodies are trending along a fault that can be followed for at least 100 m (328 ft) and vary in width from a few tens of centimeters to as much as 10 m (~1–33 ft). Petrography, geochemistry, and high homogenization temperature of fluid inclusions all point to the formation of the dolomite along a normal fault under deep burial conditions during the Middle to Late Cretaceous. The high 87 Sr/ 86 Sr ratio in the dolomite and the high salinity measured in fluid inclusions indicate that the dolomitizing fluids are deep basinal brines that interacted with crystalline basement. The dolomitization styles have an impact on the dimension, texture, and geochemistry of the different dolomite geobodies, and a modified classification scheme (compared to the one from Jung and Aigner, 2012 ) is proposed to incorporate diagenetic geobodies in future reservoir modeling.
    Print ISSN: 0149-1423
    Electronic ISSN: 0149-1423
    Topics: Geosciences
    Published by American Association of Petroleum Geologists (AAPG)
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  • 4
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    New constraints on the Pb and Nd isotopic evolution of NE Atlantic water masses (2008)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 9 (Q02007).
    Details
    Publication Date: 2018-03-08
    Description: Time series of lead (Pb) and neodymium (Nd) isotope compositions were measured on three ferromanganese crusts recording the evolution of NE Atlantic water masses over the past 15 Ma. The crusts are distributed along a depth profile (∼700–4600 m) comprising the present-day depths of Mediterranean Outflow Water and North East Atlantic Deep Water. A pronounced increase of the 206Pb/204Pb in the two deeper crusts starting at ∼4 Ma and a decrease in 143Nd/144Nd in all three crusts took place between ∼6–4 Ma and the present. These patterns are similar to isotope time series in the western North Atlantic basin and are consistent with efficient mixing between the two basins. However, the changes occurred 1–3 Ma earlier in the eastern basin indicating that the northeastern Atlantic led the major change in Pb and Nd isotope composition, probably due to a direct supply of Labrador Seawater via a northern route. The Pb isotope evolution during the Pliocene-Pleistocene can generally be explained by mixing between two end-members corresponding to Mediterranean Outflow Water and North East Atlantic Deep Water, but external sources such as Saharan dust are likely to have played a role as well. The Pb isotope composition of the shallowest crust that grew within the present-day Mediterranean Outflow Water does not show significant Pb isotope changes indicating that it was controlled by the same Pb sources throughout the past 15 Ma.
    Type: Article , PeerReviewed
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  • 5
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    Deep and bottom water export from the Southern Ocean to the Pacific Ocean over the past 38 million years (2004)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 19 . PA1020.
    Details
    Publication Date: 2017-01-26
    Description: The application of radiogenic isotopes to the study of Cenozoic circulation patterns in the South Pacific Ocean has been hampered by the fact that records from only equatorial Pacific deep water have been available. We present new Pb and Nd isotope time series for two ferromanganese crusts that grew from equatorial Pacific bottom water (D137-01, “Nova,” 7219 m water depth) and southwest Pacific deep water (63KD, “Tasman,” 1700 m water depth). The crusts were dated using 10Be/9Be ratios combined with constant Co-flux dating and yield time series for the past 38 and 23 Myr, respectively. The surface Nd and Pb isotope distributions are consistent with the present-day circulation pattern, and therefore the new records are considered suitable to reconstruct Eocene through Miocene paleoceanography for the South Pacific. The isotope time series of crusts Nova and Tasman suggest that equatorial Pacific deep water and waters from the Southern Ocean supplied the dissolved trace metals to both sites over the past 38 Myr. Changes in the isotopic composition of crust Nova are interpreted to reflect development of the Antarctic Circumpolar Current and changes in Pacific deep water circulation caused by the build up of the East Antarctic Ice Sheet. The Nd isotopic composition of the shallower water site in the southwest Pacific appears to have been more sensitive to circulation changes resulting from closure of the Indonesian seaway.
    Type: Article , PeerReviewed
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  • 6
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    The evolution of deep water mixing and weathering inputs in the central Atlantic Ocean over the past 33 Myr (2003)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 18 (4). p. 1091.
    Details
    Publication Date: 2017-01-23
    Description: The isotopic composition of Nd in present-day deep waters of the central and northeastern Atlantic Ocean is thought to fingerprint mixing of North Atlantic Deep Water with Antarctic Bottom Water. The central Atlantic Romanche and Vema Fracture Zones are considered the most important pathways for deep water exchange between the western and eastern Atlantic basins today. We present new Nd isotope records of the deepwater evolution in the fracture zones obtained from ferromanganese crusts, which are inconsistent with simple water mass mixing alone prior to 3 Ma and require additional inputs from other sources. The new Pb isotope time series from the fracture zones are inexplicable by simple mixing of North Atlantic Deep Water and Antarctic Bottom Water for the entire past 33 Myr. The distinct and relatively invariable Nd and Pb isotope records of deep waters in the fracture zones appear instead to have been controlled to a large extent by contributions from Saharan dust and the Orinoco/Amazon Rivers. Thus the previously observed similarity of Nd and Pb isotope time series from the western and eastern North Atlantic basins is better explainable by direct supply of Labrador Seawater to the eastern basin via a northern pathway rather than by advection of North Atlantic Deep Water via the Romanche and Vema Fracture Zones.
    Type: Article , PeerReviewed
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