|Biotic impact of Eocene thermal maximum 2 in a shelf setting (Dababiya, Egypt)|
Stassen, P.; Steurbaut, E.; Morsi, A.-M.M.; Schulte, P.; Speijer, R.P. (2012). Biotic impact of Eocene thermal maximum 2 in a shelf setting (Dababiya, Egypt). Austrian J. Earth Sci. 105(1): 154-160
In: Austrian Journal of Earth Sciences = Mitteilungen der Österreichischen Geologischen Gesellschaft. Austrian Geological Society: Wien. ISSN 2072-7151; e-ISSN 2072-7151
Eocene thermal maximum 2, carbon isotopes, hyperthermal, foraminifera, ostracodes, Egypt
|Auteurs|| || Top |
- Stassen, P.
- Steurbaut, E.
- Morsi, A.-M.M.
- Schulte, P.
- Speijer, R.P.
The Paleocene-Eocene thermal maximum (PETM) initiated a global biotic event with major evolutionary impacts. Since a series of minor d13C and d18O 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 studies 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 d13C excursion of approximately 1.6‰ is recorded encompassing this interval and a second negative d13C 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 d13C 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.