Palaeogene carbonate platforms under climatic and tectonic stress case studies from Egypt and Spain

Two Palaeogene carbonate platforms were studied in the Eastern Mediterranean (Egypt) and Western Mediterranean (Spain) in order to reconstruct the evolution of the shelves during times of high climatic and tectonic variability. Reconstructions are based on field observations, high-resolution microfacies (e.g., larger benthic foraminifera, corals) and geochemical data (e.g., bulk carbon isotopes). The Paleocene to Early Eocene succession of the Galala Mountains in the Eastern Desert (Egypt) represents an excellent example for an isolated carbonate platform at the SE Tethyan shelf. Deposition at the platform is controlled by syn-depositional tectonism, climate and sea-level changes. Microfacies and geochemical analyses reveal repeated phases of tectonic uplift during the Early Eocene, which are linked to the massive deposition of siliciclastics and an increasing restriction of the Egyptian shelf. The termination of tectonic uplift is indicated by the shift to pure carbonate deposition and the recovery to open ocean conditions in the latest Early Eocene. Increased nutrient availability at the Galala platform throughout the Early Eocene is interpreted as a coupled effect of climaticallyinduced nutrient discharge from the African continent and tectonically-controlled eutrophication. Carbon isotope data document three significant negative carbon isotope excursions in the Galala succession. Those excursions are related to transient global hyperthermal events. The most prominent hyperthermal event, the Paleocene-Eocene Thermal Maximum (PETM), witnesses a prominent turnover of the larger benthic foraminifera species and a shift from coral-dominated assemblages to larger benthic foraminifera-dominated assemblages at the platform. During the Early Eocene corals are not recorded in the Galala succession, which has been attributed to the coupled impact of global warming and local nutrient excess. Further post-PETM hyperthermal events were documented in the Galala succession for the first time in a shallow-marine tropical environment. The negative carbon isotope excursions of Eocene Thermal Maximum 2 and 3 show a significantly smaller magnitude and do not demonstrate a biotic impact to shallow-benthic assemblages. In a second study, a compiled Paleocene – Early Oligocene succession of the Prebetic platform in SE Spain has been used to document the distribution of larger benthic foraminifera and corals during the Eocene global cooling interval. High resolution microfacies data reveal a recovery of the Prebetic coral fauna during the Late Eocene. The comparision with other Tethyan carbonate successions demonstrates that coral recovery is strongly dependend on latitude: Global cooling yielded to the recovery of coral communities in the northern Tethyan realm during the Bartonian. A prominent cooling event at the Bartonian-Priabonian boundary, associated with a demise of many symbiontbearing larger foraminifera causes the proliferation of coral reefs in the northern Tethys and the recovery of corals in the southern Tethys. The massive temperature drop related to the Oi-1 glaciation at the Eocene-Oligocene boundary caused a transient decline in coral abundance, followed by the Tethyan-wide proliferation of major coral built-ups. Local differences regarding the timing of coral recovery are amongst others related to syn-depositional tectonic activity or temporal nutrient excess. 7 Palaeogene carbonate platforms under climatic and tectonic stress