Journal
CRETACEOUS RESEARCH
Volume 125, Issue -, Pages -Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.cretres.2021.104853
Keywords
Microfacies; Macrobenthos; Palaeoecology; Palaeoenvironment; Upper Cretaceous; Northeast Africa
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This study in the northern Eastern Desert of Egypt interprets the palaeoecology and palaeoenvironments of the Cenomanian-lower Turonian succession. The research reveals a wide spectrum of depositional features and significant palaeoecological variations influenced by different environmental parameters.
The palaeoecology and palaeoenvironments of the Cenomanian-lower Turonian succession in the northern Eastern Desert of Egypt are interpreted, based on a detailed study of macrofaunal assemblages and sedimentary facies. The abundant molluscs and echinoids of the mixed carbonate-siliciclastic Galala and Abu Qada formations have been studied in three sections with ammonites that provide a well-correlated stratigraphical framework. Three unconformities (two Cenomanian sequence boundaries and a first Turonian one) bound two third-order depositional sequences. Facies development shows a strong relationship to the sequence architecture recognised. In addition, the facies characteristics indi-cate depositional palaeoenvironments ranging from lagoonal to deep subtidal settings on a homoclinal carbonate ramp that was proximally influenced by clastic input. The macrobenthic taxa identified in 51 samples, collected from the sections studied, are grouped into seven assemblages (A-G) that are described and interpreted as remnants of communities. The faunal distribution and trophic structure of most of the assemblages recorded confirm fully oxygenated and euhaline shallow-marine environments with mesotrophic productivity level, i.e., relatively stable and low-stress conditions. The trophic structure of some other assemblages, in contrast, reflects the influence of particular environmental parameters, dissolution of aragonitic shells and/or sample size effects. Environmental parameters controlling the faunal distribution include substrate consistency, bathymetry, water energy, surface-water productivity, rate of sedimentation and oxygen availability. The integrated litho-and biofacies results certify that the sequences were deposited during an interval dominated by different perturbations that resulted in a wide spectrum of depositional features and significant palaeoecological variations. (c) 2021 Elsevier Ltd. All rights reserved.
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