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

Author(s): Douaa Fathy, Rainer Abart, Michael Wagreich, Susanne Gier, Mohamed S. Ahmed, Mabrouk Sami
Abstract: 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(s): Department of Lithospheric Research, Department of Geology
External organisation(s): Minya University, King Saud University, University of Vienna
Journal: Minerals
Volume: 13
ISSN: 2075-163X
DOI: https://doi.org/10.3390/min13020160
Publication date: 02-2023
Peer reviewed: Yes
Austrian Fields of Science 2012: 105121 Sedimentology
Keywords
ASJC Scopus subject areas: Geotechnical Engineering and Engineering Geology, Geology
Sustainable Development Goals: SDG 13 - Climate Action
Portal url: https://ucrisportal.univie.ac.at/en/publications/6a6149ff-c2ff-4b50-93b5-04e331db35e3

Back