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  • 1
    Publication Date: 2023-11-24
    Description: The Middle Miocene (15.99–11.65 Ma) of Europe witnessed major climatic, environmental, and vegetational change, yet we are lacking detailed reconstructions of Middle Miocene temperature and precipitation patterns over Europe. Here, we use a high‐resolution (∼0.75°) isotope‐enabled general circulation model (ECHAM5‐wiso) with time‐specific boundary conditions to investigate changes in temperature, precipitation, and δ〈sup〉18〈/sup〉O in precipitation (δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉). Experiments were designed with variable elevation configurations of the European Alps and different atmospheric CO〈sub〉2〈/sub〉 levels to examine the influence of Alpine elevation and global climate forcing on regional climate and δ〈sup〉18〈/sup〉Op patterns. Modeling results are in agreement with available paleobotanical temperature data and with low‐resolution Middle Miocene experiments of the Miocene Model Intercomparison Project (MioMIP1). However, simulated precipitation rates are 300–500 mm/yr lower in the Middle Miocene than for pre‐industrial times for central Europe. This result is consistent with precipitation estimates from herpetological fossil assemblages, but contradicts precipitation estimates from paleobotanical data. We attribute the Middle Miocene precipitation change in Europe to shifts in large‐scale pressure patterns in the North Atlantic and over Europe and associated changes in wind direction and humidity. We suggest that global climate forcing contributed to a maximum δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉 change of ∼2‰ over high elevation (Alps) and ∼1‰ over low elevation regions. In contrast, we observe a maximum modeled δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉 decrease of 8‰ across the Alpine orogen due to Alpine topography. However, the elevation‐δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉 lapse rate shallows in the Middle Miocene, leading to a possible underestimation of paleotopography when using present‐day δ〈sup〉18〈/sup〉O〈sub〉p〈/sub〉—elevation relationships data for stable isotope paleoaltimetry studies.
    Description: Key Points: A high‐resolution isotope‐enabled general circulation model is used to explore Middle Miocene climate and precipitation δ〈sup〉18〈/sup〉O across Europe. Middle Miocene bi‐directional precipitation change consistent with herpetological fossils and account for precipitation δ〈sup〉18〈/sup〉O variations. Global Miocene climate forcing contributed a max δ〈sup〉18〈/sup〉O change of ∼2‰ over the high Alpine elevation and to ∼1‰ over low elevation.
    Description: German research fondation
    Description: Alexander‐von‐Humboldt foundation, Feodor‐Lynen‐Fellowship
    Description: Alexander‐von‐Humboldt foundation, Humboldt Research Fellowship
    Description: Scientific Steering Committee
    Description: https://mpimet.mpg.de/fileadmin/projekte/ICON-ESM/mpi-m_sla_201202.pdf
    Description: https://gitlab.awi.de/mwerner/mpi-esm-wiso
    Description: https://zenodo.org/record/6308475#.Y0gmDSFS-2w
    Keywords: ddc:550.724 ; Europe ; Middle Miocene ; climate modeling ; stable water isotopes ; temperature ; precipitation ; paleoclimate ; paleoelevation ; Alps
    Language: English
    Type: doc-type:article
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  • 2
    Publication Date: 2023-11-24
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Uplift of the Tian Shan range modified regional climate during Cenozoic aridification in Central Asia. This study presents facies analyses and Neogene oxygen and carbon isotopic records from magnetostratigraphically dated terrestrial sedimentary sections on the southern side of the intermontane Issyk‐Kul basin in the Kyrgyz Tian Shan and 〈sup〉26〈/sup〉Al/〈sup〉10〈/sup〉Be isochron burial ages from the southern and eastern sides of the basin. The δ〈sup〉18〈/sup〉O and δ〈sup〉13〈/sup〉C data show a positive ca. 2‰ shift in values between ca. 8 and 7 Ma and a change from a negative to a positive trend. This change is attributed to the upwind growth of the Kyrgyz, Kungey and Trans Ili (Zaili) ranges, which diverted the westerlies, thereby changing the Issyk‐Kul basin from a windward to a leeward position, enhancing aridification and establishing the modern‐day spring and summer precipitation regime within the basin. Two 4 to 5 Ma 〈sup〉26〈/sup〉Al/〈sup〉10〈/sup〉Be isochron burial ages constrain the onset of Sharpyl Dak deposition on the eastern side of the basin; southward paleocurrent directions there suggest the eastward growth of the Kungey range in the Pliocene. Increased subsidence on the southern side of the basin and local tectonically induced river system reorganization led to the commencement of lake formation at ca. 5 Ma, followed by a ca. 2 Ma local depositional hiatus. The transition from sandstones of the Chu sedimentary group to conglomerates of the Sharpyl Dak group, marking a change from fluvial‐alluvial deposits to a proximal alluvial fan, is dated at 2.6–2.8 Ma by 〈sup〉26〈/sup〉Al/〈sup〉10〈/sup〉Be isochron burial dating on the southern side of the basin, driven either by tectonics or Northern Hemisphere glaciation. This study concludes that the late Miocene–Pliocene northward growth of Tian Shan significantly altered environmental conditions within the range, preventing the moisture‐bearing westerlies from reaching the intermontane Issyk‐Kul basin and promoting lake formation and expansion.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The late Miocene–Pliocene northward growth of Tian Shan created an orographic barrier that diverted the moisture‐bearing westerlies and enhanced aridification in the Issyk‐Kul basin. Reorganization of the river systems and enhanced subsidence led to the formation of an internally drained lake in Pliocene. The transition from sandstone to conglomerate (Sharpyl Dak group) deposition, linked to a change in climate and/or tectonic activity, occurred diachronously within the basin.〈boxed-text position="anchor" content-type="graphic" id="bre12751-blkfxd-0001" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:0950091X:bre12751:bre12751-toc-0001"〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: University of Wollongong http://dx.doi.org/10.13039/501100001777
    Keywords: ddc:551 ; Cenozoic aridification ; Central Asia ; cosmogenic 26Al/10Be ; tectonic uplift ; westerlies ; δ18O and δ13C stable isotopes
    Language: English
    Type: doc-type:article
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 439 (2006), S. 670-671 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Is Everest now at its highest point, or was it once even loftier? What was the greatest height attained by the vast highlands of the Tibetan plateau, and when did this occur? As described elsewhere in this issue by Rowley and Currie (page 677), these questions can be tackled — if not ...
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2018-12-10
    Description: New geochemical data from the Malawi Rift (Chiwondo Beds, Karonga Basin) fill a major spatial gap in our knowledge of hominin adaptations on a continental scale. Oxygen (δ18O), carbon (δ13C), and clumped (Δ47) isotope data on paleosols, hominins, and selected fauna elucidate an unexpected diversity in the Pleistocene hominin diet in the various habitats of the East African Rift System (EARS). Food sources of early Homo and Paranthropus thriving in relatively cool and wet wooded savanna ecosystems along the western shore of paleolake Malawi contained a large fraction of C3 plant material. Complementary water consumption reconstructions suggest that ca. 2.4 Ma, early Homo (Homo rudolfensis) and Paranthropus (Paranthropus boisei) remained rather stationary near freshwater sources along the lake margins. Time-equivalent Paranthropus aethiopicus from the Eastern Rift further north in the EARS consumed a higher fraction of C4 resources, an adaptation that grew more pronounced with increasing openness of the savanna setting after 2 Ma, while Homo maintained a high versatility. However, southern African Paranthropus robustus had, similar to the Malawi Rift individuals, C3-dominated feeding strategies throughout the Early Pleistocene. Collectively, the stable isotope and faunal data presented here document that early Homo and Paranthropus were dietary opportunists and able to cope with a wide range of paleohabitats, which clearly demonstrates their high behavioral flexibility in the African Early Pleistocene.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 5
    Publication Date: 2016-09-12
    Description: At global and regional scales, primary productivity strongly correlates with richness patterns of extant animals across space, suggesting that resource availability and climatic conditions drive patterns of diversity. However, the existence and consistency of such diversity–productivity relationships through geological history is unclear. Here we provide a comprehensive quantitative test of the diversity–productivity relationship for terrestrial large mammals through time across broad temporal and spatial scales. We combine 〉14,000 occurrences for 690 fossil genera through the Neogene (23–1.8 Mya) with regional estimates of primary productivity from fossil plant communities in North America and Europe. We show a significant positive diversity–productivity relationship through the 20-million-year record, providing evidence on unprecedented spatial and temporal scales that this relationship is a general pattern in the ecology and paleo-ecology of our planet. Further, we discover that genus richness today does not match the fossil relationship, suggesting that a combination of human impacts and Pleistocene climate variability has modified the 20-million-year ecological relationship by strongly reducing primary productivity and driving many mammalian species into decline or to extinction.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 6
    Publication Date: 2013-02-01
    Description: Paleoelevation reconstructions of mountain belts and orogenic plateaus based on stable isotope climate and precipitation records benefit greatly from present-day calibrations that relate the fractionation of hydrogen (δD) and oxygen (δ18O) isotopes in precipitation to orographic rainfall. Here, we establish a first-order template of δD and δ18O of modern meteoric waters across the Central Anatolian Plateau (CAP) and its bordering Pontic and Taurus Mountains. We identify key regions in the plateau interior and along the plateau margins that have the potential to reliably record topography-related paleotemperature and paleoprecipitation changes as recovered from stable isotope paleosol, fossil teeth or lipid proxy data. Based on δD and δ18O data of more than 480 surface water samples from small catchments and springs, we characterize moisture sources affecting the net isotopic budget of precipitation over the CAP and analyze how orographic rainout and plateau aridity shape modern patterns of δD and δ18O in precipitation. The Taurus Mountains bordering the CAP to the south act as a major orographic barrier for transport of predominantly winter moisture and exhibit isotopic lapse rates of approximately −20‰/km for δD and −2.9‰/km for δ18O across an elevation range of nearly 3000 m. The Pontic Mountains at the northern margin of the CAP force perennial moisture to ascend and condensate revealing lapse rates of −19‰/km for δD and −2.6‰/km for δ18O. The difference in the predominant moisture source for the southern and northern margins of the CAP (North African versus Atlantic air masses) is manifested in systematic north-south differences in near-sea level meteoric water compositions of Δ(δDN-S) ∼20 permil and Δ(δ18ON-S) ∼3 permil in a swath across the central part of the plateau. Stable isotope data from the semi-arid plateau interior with rainfall as low as 300 to 500 mm/yr and mean summer temperatures attaining 23 °C, provide clear evidence for an evaporative regime that drastically affects surface water and runoff compositions and results in a local meteoric water line for the plateau interior that follows δD = 4.0 · δ18O − 29.3. Strongly evaporitic conditions contrast rainfall patterns along the plateau margins including their immediate leeward flanks where δD- and δ18O-elevation relationships are reliable predictors of modern topography.
    Print ISSN: 0002-9599
    Electronic ISSN: 1945-452X
    Topics: Geosciences
    Published by HighWire Press on behalf of The American Journal of Science.
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  • 7
    Publication Date: 2011-01-01
    Description: Continental topography is the result of complex interactions among mantle convection, continental dynamics, and climatic and erosional processes. Therefore, topographic evolution of mountain belts and continental interiors reflects directly upon the coupling between mantle and surface processes. It has recently been proposed that the modern topography of western North America is partly controlled by the removal of the subducting Farallon plate and replacement of lithospheric mantle by hot asthenosphere, creating surface uplift of the Colorado Plateau, the southwestern United States, and northern Mexico, while concomitant subsidence characterizes the central United States. How the topography of the Cenozoic North American Cordillera evolved in the past is largely unknown, yet currently debated tectonic models each have a predictable topographic response. Here we examine Cenozoic surface uplift patterns of western North America based on a record of [~]3000 stable isotope proxy data. This data set is consistent with Eocene north to south surface uplift in the Cordillera, culminating in the assembly of an Eocene-Oligocene highland 3-4 km in elevation. The diachronous record of surface uplift and associated magmatism further supports tectonic models calling for the convective removal of mantle lithosphere or removal of the Farallon slab by buckling along an east-west axis. The Eocene-Oligocene development of rainout patterns similar to present-day patterns along the flanks of the Cordilleran orogen is therefore unlikely to be the result of late Mesozoic crustal thickening and associated development of an Andean-style Altiplano.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 8
    Publication Date: 2012-02-01
    Description: Herein we present oxygen isotope records from Cretaceous to Recent terrestrial sediments in the western North American Cordillera. The purpose of this analysis is to use oxygen isotope records to understand the coupled surface elevation and climate histories of this region through the Cenozoic. To do this we constructed δ18O maps of surface waters for time intervals that trace the development of topography of western North America. These maps are based on 4861 oxygen isotope analyses from both published (4478) and new (383) data. We determined the δ18O values of surface waters using paleotemperatures derived previously from floral assemblages and the appropriate isotope fractionation factors. These data suggest that in the late Cretaceous to early Eocene the Sevier hinterland formed a plateau of unknown height. Around 50 Ma, a topographic wave developed in British Columbia and eastern Washington that swept southward reaching northeastern Nevada at ∼40 to 38 Ma, and southern Nevada ∼23 Ma. This southward encroachment of an Eocene Plateau (SWEEP) caused reorganization of drainage patterns such that the intraforeland basins of Wyoming and Utah drainages extended deep within the Sevier hinterland as the wave swept southward. The landscape within the Sevier hinterland developed into a rugged and high mountain range with the hypsometric mean elevation of ∼4 km and relief of ∼1.5 km. This Eocene highland was bordered on the west by a high Sierra Nevada ramp and on the east by the intraforeland basins that captured water draining these growing highlands. The spatial and temporal evolution of this highland correlates with the timing of volcanism and extension. These observations support tectonic models that call for north to south removal of the Farallon slab or piecemeal removal of mantle lithosphere.The isotopic data show that prior to growth of this highland the North American Monsoon (NAM) penetrated much farther north in the Paleocene/Eocene than today. The combined effects of global cooling, increasing latitudinal temperature gradients, and the generation of the orographic barrier created by the growing north to south highland produced a southward migration of the NAM front. By the Oligocene the hydrologic regime that we observe today was in place. It has been modified since then as a result of Basin and Range extension and collapse of the highlands in the mid-Miocene. This collapse allowed the NAM to penetrate farther north into the Great Basin of Nevada and Utah.
    Print ISSN: 0002-9599
    Electronic ISSN: 1945-452X
    Topics: Geosciences
    Published by HighWire Press on behalf of The American Journal of Science.
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  • 9
  • 10
    Publication Date: 2020-05-14
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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