Biotic impact of Eocene thermal maximum 2 in a shelf setting (Dababiya, Egypt).



Biotic impact of Eocene thermal maximum 2 in a shelf setting (Dababiya, Egypt).

TitelBiotic impact of Eocene thermal maximum 2 in a shelf setting (Dababiya, Egypt).
PublicatietypeJournal Article
Year of Publication2012
AuteursStassen, P, Steurbaut, E, Morsi, A-MM, Schulte, P, Speijer, RP
JournalAustrian Journal of Earth Sciences
Date PublishedApril
TrefwoordenGeology, Paleontology

The Paleocene-Eocene thermal maximum (PETM) initiated a global biotic event with major evolutionary impacts. Since a series of minor $δ$13C and $δ$18O excursions, indicative of hyperthermals, now appears to characterize early Eocene climate, it remains to be investigated how the biosphere responded to these warming events. We studied the Esna Formation at Dababiya (Nile Basin, Egypt), in order to identify Eocene thermal maximum 2 (ETM-2) and to evaluate the foraminiferal and ostracode patterns. The studied interval generally consists of gray-brown marls and shales and is interrupted by a sequence of deviating lithologies, representing an early Eocene Egyptian environmental perturbation that can be linked to ETM-2. The ETM-2 interval consists of brownish shales (bed 1) to marls (bed 2) at the base that grade into a foraminifera-rich chalky limestone (bed 3) at the top. This conspicuous white limestone bed forms the base of the Abu Had Member. A distinct negative $δ$13C excursion of approximately 1.6‰ is recorded encom- passing this interval and a second negative $δ$13C shift of 1‰ occurs 5 m higher. These two isotope events are situated respectively in the basal and lower part of the calcareous nannoplankton zone NP11 and appear to correlate with the H1 and H2(?) excursions observed in the deep-sea records. The lower $δ$13C excursion is associated with benthic foraminiferal and ostracode changes and settlement of impoverished anomalous foraminiferal (planktic and benthic) assemblages, indicating a transient environmental anomaly, disrupting the entire marine ecosystem during ETM-2. Our observations indicate some similarities between the sedimentary and biotic expressions of ETM-2 and the PETM at Dababiya, pointing to similar processes operating in the Egyptian Basin during these global warming events.

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