NEOTETHYS · The Late Eocene climatic transition from greenhouse to icehouse conditions in the Neo-Tethys

The Late Eocene climatic transition from greenhouse to icehouse conditions in the Neo-Tethys

Project context and objectives The period from the early Eocene to early Oligocene (~55 to 28 million years - Ma) represents an important time interval for Cenozoic paleoclimatic and paleogeographic evolution. Stable isotope records (d18O and d13C) from pelagic foraminifera show a long-term cooling trend through the Eocene, which ends with an abrupt step, the Oi-1, near the Eocene-Oligocene (E-O) transition at ~34 Ma, interpreted to reflect the glaciation of Antarctica. My hypothesis proposed that this climate step was also triggered by the closure of the Arabian-Asian gateway in a progression of stepwise variations in sea level and ocean circulation. In the middle to late Eocene (~49 to 34 Ma), deep-sea paleoceanographic records also indicate a strong, transient warming event (Middle Eocene climate optimum - MECO). Work performed Within the framework of this project, I have obtained high-resolution integrated magnetostratigraphic and paleoenvironmental analysis, including biostratigraphy (calcareous nannofossils and foraminifera), environmental magnetism, wt. % CaCO3, and stable isotope records, for DSDP/ODP holes in the Indian Ocean (214, 217, 219, 242, 709C, 711A, 738B, 749B, 757B, and 757C) and outcropping sections in Italy (Mt Cagnero, Massignano and Gubbio) and Turkey (Baskil). The combined results for these sections provide a continuous paleoceanographic history for the early Eocene - early Oligocene interval from the main sequences of the western, central and eastern Neo-Tethys. I also obtained the first environmental magnetic data from most of these sections in addition to rock magnetic studies. The main climatic events are recognised in the preliminary results by the occurrence of single domain magnetite (mixed with fine hematite in the inland sections) in specific rock magnetic behaviour that can be related to the evolution of paleoceanographic conditions. This project involved both field and laboratory work. Extensive studies to define the best stratigraphical sections to accomplish the aimed results were developed during a month in Egypt, almost two months in Turkey and two months in Italy. Detailed sampling was undertaken in one or more key stratigraphic sections in Italy (three field trips), Egypt (one field trip) and Turkey (two field trips). Main results The results of this study have a wide impact since new and important outlines have been discovered on the paleoclimatic events before and on the Eocene-Oligocene transition. The development of these high-resolution records of climate and environmental change from the Eocene to the E-O transition interval are an important contribution of new data for a crucial interval of Earth history. The areas where the analysis was performed are paleoceanographically sensitive and enable testing of different hypotheses for the origin of the global climatic deterioration in the earliest Oligocene. There is considerable international scientific interest in the problems being addressed. Thus, this study on the interaction of those stratigraphical sections in the Neo-Tethys realm provided the basis for further investigations and models to help formulate new paleoceanographic reconstructions and to understand causes and consequences of the paleoclimatic and paleoceanographic circulation before and along the Eocene-Oligocene transition. This project will promote new research to be developed in the future starting from these studies; this is why several manuscripts corresponding to these results will be submitted soon for publication.

Data: CORDIS, © European Union