Late Campanian Climatic-Continental Weathering Assessment and Its Influence on Source Rocks Deposition in Southern Tethys, Egypt

Autor(en): Douaa Fathy, Rainer Abart, Michael Wagreich, Susanne Gier, Mohamed S. Ahmed, Mabrouk Sami
Abstrakt: Climatic variability and silicate weathering are remarkable features throughout the Late Cretaceous period. Late Campanian black shale is considered the most significant silicate source rock in the southern Tethys. Here, we used mineralogical and geochemical data to evaluate the continental weathering intensity and climatic changes as well as their impact on the deposition of the Late Campanian black shale in the Western Desert of Egypt. The studied black shale has a relatively high concentration of Al, Fe, Mg, Ca, Sr, Ga, Co, Cr, and V when compared to the average Post-Archean Australian Shales (PAAS). The studied samples have elevated values of Ga/Rb, and low values of Rb/Sr, Sr/Cu, and K₂O/Al₂O₃, supporting the deposition of Late Campanian shale under warm/humid conditions. Furthermore, the average chemical index of alteration (CIA, 78.6%), chemical index of weathering (CIW; 83.8%), C-value (1.26), Fe/Mn (408), and Mg/Ca (1.54) reveal the predominance of warm/humid climate. The chemical weathering proxies (CIA, CIW, PIA, LnAl₂O₃/Na₂O) and ACNK diagram imply that the Late Campanian samples were exposed to a moderate grade of chemical alteration. The deposition of black shale occurred under high seawater salinity conditions based on Sr/Ba (Avg = 3.6). Additionally, the weathering indices are well correlated with paleoclimatic proxies, suggesting that weathering intensity is strongly affected by paleoclimate. However, chemical weathering during the Late Campanian has a weak influence on oceanic nutrient fluxes. No substantial impact of the paleoclimate during the deposition of Late Campanian black shale on water salinity was reported.
Organisation(en): Department für Lithosphärenforschung, Institut für Geologie
Externe Organisation(en): Minya University, King Saud University, Universität Wien
Journal: Minerals
Band: 13
ISSN: 2075-163X
DOI: https://doi.org/10.3390/min13020160
Publikationsdatum: 02-2023
Peer-reviewed: Ja
ÖFOS 2012: 105121 Sedimentologie
Schlagwörter
ASJC Scopus Sachgebiete: Geotechnical Engineering and Engineering Geology, Geology
Sustainable Development Goals: SDG 13 – Maßnahmen zum Klimaschutz
Link zum Portal: https://ucrisportal.univie.ac.at/de/publications/6a6149ff-c2ff-4b50-93b5-04e331db35e3

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