Biostratigrafia e paleoceanografia di sedimenti provenienti dall'Oceano indiano equatorial

C. Fioroni

F. Florindo

G. Villa

English

Archivio istituzionale della ricerca - Università di Modena e Reggio Emilia

Geophysical Research AbstractsVol. 20, EGU2018-17514, 2018EGU General Assembly 2018© Author(s) 2018. CC Attribution 4.0 license.Paleogene calcareous nannofossil biostratigraphic updates fromequatorial Indian OceanChiara Fioroni (1), Giuliana Villa (2), and Fabio Florindo (3)(1) Dipartimento di Scienze Chimiche e Geologiche, Modena and Reggio Emilia University, Italy (chiara.fioroni@unimore.it),(2) Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale, Parma University, Italy(giuliana.villa@unipr.it), (3) Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy (fabio.florindo@ingv.it)ODP Sites 709 and 711 are located on the Madingley Rise, a local topographic high between the MascarenePlateau and the Carlsberg Ridge in the Equatorial Indian Ocean, and drilled in the eighties, recovering sedimentsspanning the middle Eocene –Pleistocene time interval. The Paleogene nannofossil biostratigraphy was carriedout by Okada (1980), and later Site 711 was further investigated by means of nannofossils for a paleoecologic andpaleoceanographic study (Wei, Villa and Wise, 1992).In the last two decades high resolution sampling from different oceanic and on land settings led to a detailednannofossil biostratigraphy (e.g. Agnini et al., 2014) based on taxonomic updates. The recognition of several newnannofossil species is offering the opportunity to improve the biostratigraphic resolution and to achieve a detailedmiddle Eocene-early Oligocene biochronology.On this basis, we present a new magnetostratigraphy, quantitative calcareous nannofossil analyses on a highresolution sample set, in order to reassess the middle Eocene to lower Oligocene biostratigraphy of both sites 711and 709. Here we discuss 30 bioevents, spanning an interval of about 13 Myr (Chron C20 to Chron C12), andcompare our results with previous data related to the Indian Ocean, and the recent biozonations established forlow and middle latitudes.The detailed time frame obtained is fundamental to place the paleoceanographic events, crucial in this timeinterval encompassing the Middle Eocene Climatic Optimum (MECO) and the long cooling trend that leads to theOligocene glacial state. Nannofossil response to the paleoclimatic changes highlights a turnover in the assemblageshowing an increase in eutrophic taxa and a decrease in oligotrophic and warm species just before the inceptionof the EOT (Eocene-Oligocene boundary), indicating a shift toward increased nutrient availability at the surfacewaters of the equatorial Indian Ocean.REFERENCESOkada, H., 1990. Quaternary and Paleogene calcareous nannofossils, Leg 115. In: Duncan, R.A., Backman, J.,Peterson, L.C., et al. (Eds.), Proceedings ODP. Scientific Results 115. Ocean Drilling Program, College Station,TX, pp. 129–174.Wei, W., Villa, G., Wise Jr., S.W., 1992. Paleoceanographic implications of Eocene- Oligocene calcareousnannofossils from Sites 711 and 748 in the Indian Ocean. In: Wise Jr., S.W., Schlich, R., et al. (Eds.), ProceedingsODP. Scientific Results 120, pp. 979–999.

Paleogene calcareous nannofossil biostratigraphic updates from equatorial Indian Ocean

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Paleogene calcareous nannofossil biostratigraphic updates from equatorial Indian Ocean

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