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  • 1
    Electronic Resource
    Electronic Resource
    Late Cretaceous deep-water agglutinated foraminiferal assemblages from the North Atlantic and its marginal seas (1989)
    Springer
    International journal of earth sciences 78 (1989), S. 1121-1140 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract The stratigraphic and biogeographic distribution of more than 170 species of deep-water agglutinated benthic foraminifers (DWAF) from the North Atlantic and adjacent marginal seas has been compared with paleoenvironmental data (e.g. paleobathymetry, oxygenation of the bottom waters, amount of terrigenous input and substrate disturbance). Six general types of assemblages, in which deep water agglutinated taxa occur, are defined from the Turonian to Maastrichtian times: 1. High latitude slope assemblages 2. Low to mid latitude slope assemblages 3. Flysch-type assemblages 4. Deep water limestone assemblages (»Scaglia«-type) 5. Abyssal mixed calcareous-agglutinated assemblages 6. Abyssal purely agglutinated assemblages Latitudinal differences in faunal composition are observed, the most important of which is the lack or extreme paucity of calcareous forms in high latitude assemblages. East-to-west differences appear to be of comparatively minor importance. Most DWAF species occur in all studied regions and are thus considered as cosmopolitan. Biostratigraphic turnovers in the taxonomic content of assemblages are observed in the lowermost Turonian, mid- Campanian and in the upper Maastrichtian to lowermost Paleocene. These datum levels correspond to inter-regional and time-constant paleooceanographic events, which probably also affected the deep-water benthic biota. This allows us to use deep-water agglutinated foraminifers for biostratigraphy in the North Atlantic sequences deposited below CCD and to geographically extend the currently used zonal schemes which have been established in the Carpathian and Alpine areas.
    Abstract: Résumé La répartition stratigraphique et biogéographique de plus de cent soixante dix espèces de foraminifères benthiques agglutinants d'eaux profondes de l'Océan Atlantique Nord et des mers adjacentes a été examinée en fonction des paramètres du paléoenvironnement (paléobathymétrie, oxygénation et dynamique des eaux de fond, apports détritiques terrigènes). Sur une période s'étendant du Turonien au Maestrichtien, six types principaux d'associations, comprenant en tout ou partie des taxons agglutinants profonds, ont été définis: 1. associations de talus en haute latitude 2. associations de talus en basse latitude 3. associations de type flysch 4. associations de calcaires pélagiques (type »Scaglia«) 5. associations abyssales de type mixte avec foraminifères à test calcaire et foraminifères agglutinants 6. associations abyssales uniquement composées d'agglutinants. Des différences latitudinales sont apparues dans la composition faunique: la plus importante réside dans l'absence ou la très grande rareté des formes à test calcaire dans les associations de haute latitude. Des différences en longitude, d'est en ouest, apparaissent comparativement d'importance mineure. La plupart des espèces de foraminifères agglutinants d'eaux profondes se rencontrent dans toutes les régions étudiées et peuvent donc être considérées comme ubiquistes. De nettes coupures biostratigraphiques, fondées sur des renouvellements fauniques, sont décelées au Turonien basal, au Campanien moyen et au passage Meastrichtien supérieur-Paléocène basal. Ces niveaux repères correspondent à des événements paléo-océanographiques isochrones et d'extension supra-régionale, qui ont probablement affecté aussi les formes benthiques d'eaux profondes. Ceci nous incite à utiliser les foraminifères benthiques profonds pour la biostratigraphie des séries Nord-Atlantique déposées sous la CCD et par corrélation nous permet d'étendre géographiquement l'usage de zonations initialement définies dans le domaine alpino-carpathique.
    Notes: Zusammenfassung Die stratigraphische und biogeographische Verbreitung von mehr als 170 Arten sandschaliger benthischer Tiefwasser-Foraminiferen wurde im Nordatlantik und seinen Randmeeren untersucht. Hierbei wurden die in den einzelnen Untersuchungsgebieten unterschiedlichen Paläoenvironment- Bedingungen (Wassertiefe, Sauerstoffverhältnisse am Ozeanboden, detritischer Eintrag und Beeinträchtigung des Substrats durch Strömungs- und Sedimentationsprozesse) zu der jeweiligen taxonomischen Zusammensetzung der agglutinierenden Benthos-Fauna in Beziehung gesetzt. Für den Zeitraum vom Turon bis zum Maastricht ließen sich zwölf charakteristische Vergesellschaftungen agglutinierender Tiefwasser-Foraminiferen unterscheiden, die in sechs Hauptgruppen zusammengefaßt werden können: 1. Kontinentalhang-Vergesellschaftungen hoher Breiten 2. Kontinentalhang-Vergesellschaftungen niedriger bis mittlerer Breiten 3. Flysch-Vergesellschaftungen 4. Vergesellschaftungen pelagischer Kalke (»Scaglia«-Typ) 5. Abyssale gemischt kalkschalige und agglutinierende Benthos-Vergesellschaftungen 6. Abyssale rein agglutinierende Vergesellschaftungen Biogeographische Unterschiede in der Faunenzusammensetzung korrelieren vor allem mit der geographischen Breite, wobei besonders das Fehlen kalkschaliger Elemente in Faunen hoher Breiten auffällt. Ost-West-Unterschiede sind von geringerer Bedeutung, die Mehrzahl der Arten tritt in allen untersuchten Gebieten auf und kann als kosmopolitisch angesehen werden. Faunenschnitte können im basalen Turon, im mittleren Campan und an der Kreide/Tertiär-Grenze beobachtet werden. Diese Zeitabschnitte sind durch überregionale paläoozeanographische Events charakterisiert, die wahrscheinlich auch das Tiefsee-Benthos beeinflußt haben. Dieser Zusammenhang zwischen der Evolution agglutinierender Tiefsee- Foraminiferen und globalen, zeitkonstanten Events ermöglicht eine biostratigraphische Gliederung der Sub-CCD Serien des Nordatlantik mit Hilfe sandschaliger Foraminiferen, die sich weitgehend mit den Zonierungen, die in den Flyschzonen der Karpathen und Alpen entwickelt wurden, korrelieren läßt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01829336
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  • 2
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    Cool episodes in the Late Cretaceous - exploring the effects of physical forcing on Antarctic snow accumulation (2010)
    Copernicus Ges.
    In:  [Poster] In: EGU General Assembly, 02.05.-07.05.2010, Vienna, Austria . Geophysical Research Abstracts ; EGU2010-9334 .
    Details
    Publication Date: 2019-09-23
    Description: Until recently it was assumed that the major modern ice sheets on Antarctica became established around the Eocene-Oligocene boundary about 34 Ma ago. But new evidence (e.g. Miller et al., 2008) indicates that continental ice may have been present much earlier, some of it probably even since the greenhouse times of the Late Cretaceous. Deep sea drilling data suggest changes in sea-level during the Late Cretaceous that could have been caused by the melting and freezing of vast ice sheets on Antarctica. Using a GCM approach to test the whether it would be possible to generate the described high-amplitude sealevel falls is one additional way to test this vigorously discussed issue. As shown above, our numerical approach indicates the possibility of a substantial Antarctic glaciation by changing the physical boundary conditions, eccentricity, pCO2, and elevation within reasonable Late Cretaceous ranges. Our simulations suggest that simulated snowfall and consecutive ice formation on Antarctica might yield sufficient volumes to account for the documented rapid, low-amplitude Cretaceous sea-level fluctuations. Based on cautious assumptions and possible errors the model results show that ice build-up could take place in realistic time spans and in accordance with the proxy records. Thus, the possibility of an Antarctic ice shield build-up large enough to drive sea level fluctuations on the order of tens of meters within 20,000-220,000 years is supported. The initial snow accumulation and following growth of Antarctic ice-sheets in the Cretaceous can be attributed to changes in southern hemisphere summer insolation due to reduced orbital eccentricity. Alternatively and/or additionally, declining atmospheric CO2 values caused further cooling
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Poster
  • 3
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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)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bretschneider, L., Hathorne, E. C., Bolton, C. T., Gebregiorgis, D., Giosan, L., Gray, E., Huang, H., Holbourn, A., Kuhnt, W., & Frank, M. Enhanced late miocene chemical weathering and altered precipitation patterns in the watersheds of the Bay of Bengal recorded by detrital clay radiogenic isotopes. Paleoceanography and Paleoclimatology, 36(9), (2021): e2021PA004252, https://doi.org/10.1029/2021PA004252.
    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 analyzed 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 focused 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.
    Description: This research used samples and data provided by the International Ocean Discovery Program and was funded by the German Research Foundation (DFG) (grants HA 5751/6-1 & -2). C. T. Bolton acknowledges funding from the French ANR project iMonsoon (ANR-16-CE01-0004-01) and IODP France. W. Kuhnt acknowledges funding from the DFG (grant Ku649/36-1).
    Keywords: Clay radiogenic isotopes ; Late Miocene ; South Asian Monsoon ; Chemical weathering
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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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)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bretschneider, L., Hathorne, E. C., Huang, H., Luebbers, J., Kochhann, K. G. D., Holbourn, A., Kuhnt, W., Thiede, R., Gebregiorgis, D., Giosan, L., & Frank, M. Provenance and weathering of clays delivered to the Bay of Bengal during the middle Miocene: linkages to tectonics and monsoonal climate. Paleoceanography and Paleoclimatology, 36(2), (2021): e2020PA003917, https://doi.org/10.1029/2020PA003917.
    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 toward 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.
    Description: This research used samples and data provided by the International Ocean Discovery Program and was funded by the German Research Foundation (DFG) (grants HA 5751/6‐1 and HA 5751/6‐2, KU 649/36‐1, and TH 1317‐8 and TH 1317‐9). Open access funding enabled and organized by Projekt DEAL.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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