Abrupt climatic, oceanographic and ecologic changes near the Paleocene-Eocene transition in the deep Tethys Basin: The Alademilla section, southern Spain

The Tethys is a critical region for investigating the mechanism(s) of the Paleocene-Eocene global change, because of its potential in producing warm saline water masses, a possible driving force for the deep ocean warming at this time. To examine climatic, oceanographic and ecologic changes in the deep Tethys basin, we conducted high resolution faunal, isotopic and mineralogic analyses across the P-E transition at the Alamedilla section (paleodepth between 1000 m and 2000 m) in southern Spain. At this location, foraminiferal δ¹⁸O values show little temperature change in surface waters, but a 4 °C warming in bottom waters. Comparison with deep-sea sites indicates that Antarctic intermediate water was consistently colder than Tethys bottom water. During the course of the P-E global change, however, the temperature difference between these two water masses was reduced from a previous 5 °C to 3 °C. Clay mineralogic analyses at the Alamedilla section indicate increased aridity in the Tethys region that contrasts with a humid episode on Antarctica during high-latitude warming. Foraminiferal δ¹³C values at Alamedilla show a negative excursion of 1.7‰ in both surface and bottom waters with little change in the vertical δ¹³C gradient. Accumulation of organic and inorganic carbon in sediments decreased significantly, suggesting changes in the size and structure of the oceanic carbon reservoir. Associated with these climatic and oceanographic changes is a reorganization of the Tethys ecosystem, a benthic foraminiferal mass extinction, and planktonic foraminiferal assemblages marked by increased species turnover rates and high relative abundance of short-lived, opportunistic species that suggest increased instability.