Large Ecosystem Perturbations: Causes and Consequences pages:53-67
Geological Society of America, Special Paper 424
International Geological Conference edition:32 location:Florence date:20-28 August 2004
In the present study, we investigate upper Paleocene to lower Eocene planktic forami niferal assemblages in Egypt and Jordan across a middle neritic to upper bathyal transect of the Tethyan continental margin. In particular, we evaluate the planktic foraminiferal turnover across the Paleocene-Eocene Thermal Maximum (PETM). Dissolution affects the planktic assemblages more intensively than previously considered, especially in the marls below the PETM. High numbers of Subbotina, fluctuating planktic/benthic (P/B) ratios, and low numbers of planktic foraminifera per gram (PFN) are indicative of dissolution, probably as a consequence of deep weathering. Hence, high numbers of Subbotina in this area do not indicate cooling. Despite this taphonomic overprint, we observe that well-diversifi ed planktic foraminiferal assemblages of Subzone P5a abruptly changed into oligotaxic assemblages dominated by Acarinina during the PETM. Because various biotic and geochemical proxies indicate increased nutrient supply to the basin, we argue that the blooming of Acarinina is not indicative of oligotrophic conditions. Instead, we postulate that (low-trochospiral) Acarinina may have been better adapted to thrive under stressed environmental conditions, possibly because they hosted symbionts different from those in Morozovella.