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  • 1
    Electronic Resource
    Electronic Resource
    Impacts of orbital forcing and atmospheric carbon dioxide on Miocene ice-sheet expansion (2005)
    [s.l.] : Nature Publishing Group
    Nature 438 (2005), S. 483-487 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The processes causing the middle Miocene global cooling, which marked the Earth's final transition into an ‘icehouse’ climate about 13.9 million years ago (Myr ago), remain enigmatic. Tectonically driven circulation changes and variations in atmospheric carbon dioxide levels ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature04123
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    Paper (German National Licenses)
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  • 2
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    Unraveling the onset of Cretaceous Oceanic Anoxic Event 2 in an extended sediment archive from the Tarfaya-Laayoune Basin, Morocco (2017)
    AGU (American Geophysical Union) | Wiley
    In:  Paleoceanography, 32 (8). pp. 923-946.
    Details
    Publication Date: 2020-02-06
    Description: We investigated the onset and development of Cretaceous Oceanic Anoxic Event 2 (OAE2) in a newly drilled core (SN degrees 4) from the Tarfaya Basin (southern Morocco), where this interval is unusually expanded. High-resolution (centimeter-scale equivalent to centennial) analysis of bulk organic and carbonate stable isotopes and of carbonate and organic carbon content in combination with XRF scanner derived elemental distribution reveal that the ocean-climate system behaved in a highly dynamic manner prior to and during the onset of OAE2. Correlation with the latest orbital solution indicates that the main carbon isotope shift occurred during an extended minimum in orbital eccentricity (similar to 400 kyr cycle). Shorter-term fluctuations in carbonate and organic carbon accumulation and in sea level related terrigenous discharge were predominantly driven by variations in orbital obliquity. Negative excursions in organic and carbonate delta C-13 preceded the global positive delta C-13 shift marking the onset of OAE2, suggesting injection of isotopically depleted carbon into the atmosphere. The main delta C-13 increase during the early phase of OAE2 in the late Cenomanian was punctuated by a transient plateau. Maximum organic carbon accumulation occurred during the later part of the main delta C-13 increase and was associated with climate cooling events, expressed as three consecutive maxima in bulk carbonate delta O-18. The extinctions of the thermocline dwelling keeled planktonic foraminifers Rotalipora greenhornensis and Rotalipora cushmani occurred during the first and last of these cooling events and were likely associated with obliquity paced, ocean-wide expansions, and intensifications of the oxygen minimum zone, affecting their habitat space on a global scale.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2017PA003146
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Provenance and weathering of clays delivered to the Bay of Bengal during the middle Miocene: Linkages to tectonics and monsoonal climate (2021)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: Tectonics and regional monsoon strength control weathering and erosion regimes of the watersheds feeding into the Bay of Bengal, which are important contributors to global climate evolution via carbon cycle feedbacks. The detailed mechanisms controlling the input of terrigenous clay to the Bay of Bengal on tectonic to orbital timescales are, however, not yet well understood. We produced orbital‐scale resolution geochemical records for International Ocean Discovery Program Site U1443 (southern Bay of Bengal) across five key climatic intervals of the middle to late Miocene (15.8 – 9.5 Ma). Our new radiogenic Sr, Nd, and Pb isotope time series of clays transported to the Ninetyeast Ridge suggest that the individual contributions from different erosional sources overall remained remarkably consistent during the Miocene despite major tectonic reorganizations in the Himalayas. On orbital timescales, however, high‐resolution data from the five investigated intervals show marked fluctuations of all three isotope systems. Interestingly, the variability was much higher within the Miocene Climatic Optimum (around 16‐15 Ma) and across the major global cooling (~13.9‐13.8 Ma) until ~13.5 Ma, than during younger time intervals. This change is attributed to a major restriction on the supply of High Himalayan erosion products due to migration of the peak precipitation area towards the frontal domains of the Himalayas and the Indo‐Burman Ranges. The transient excursions of the radiogenic isotope signals on orbital timescales most likely reflect climatically driven shifts in monsoon strength.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Enhanced late Miocene chemical weathering and altered precipitation patterns in the watersheds of the Bay of Bengal recorded by detrital clay radiogenic isotopes (2021)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: The late Miocene was a period of declining CO2 levels and extensive environmental changes, which likely had a large impact on monsoon strength as well as on the weathering and erosion intensity in the South Asian Monsoon domain. To improve our understanding of these feedback systems, detrital clays from the southern Bay of Bengal (International Ocean Discovery Program Site U1443) were analysed for the radiogenic isotope compositions of Sr, Nd, and Pb to reconstruct changes in sediment provenance and weathering regime related to South Asian Monsoon rainfall from 9 to 5 Ma. The 100 kyr resolution late Miocene to earliest Pliocene record suggests overall low variability in the provenance of clays deposited on the Ninetyeast Ridge. However, at 7.3 Ma, Nd and Pb isotope compositions indicate a switch to an increased relative contribution from the Irrawaddy River (by ∼10 %). This shift occurred during the global benthic δ13C decline and we suggest that global cooling and increasing aridity resulted in an eastward shift of precipitation patterns leading to a more focussed erosion of the Indo-Burman Ranges. Sr isotope compositions were decoupled from Nd and Pb isotope signatures and became more radiogenic between 6 and 5 Ma. Grassland expansion generating thick, easily weatherable soils may have led to an environment supporting intense chemical weathering which is likely responsible for the elevated detrital clay 87Sr/86Sr ratios during this time. This change in Sr isotope signatures may also have contributed to the late Miocene increase of the global seawater Sr isotope composition.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: other
    Format: other
    Format: other
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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