THE LATE MIOCENE BIOGENIC BLOOM: A BENTHIC FORAMINIFERA PERSPECTIVE FROM IODP SITE U1506 AND ODP SITE 1085

The Late Miocene Biogenic Bloom (LMBB, ~ 9-3.5 Ma) is a paleoceanographic event that has been traditionally described as an increased primary productivity episode and associated to changes in the marine carbon cycle. Documented in the Indian, Pacific, and Atlantic oceans, this unusual increase in primary productivity remains enigmatic because the processes and mechanisms related to this event are not yet fully understood. Different explanations for the persistent and anomalously high productivity conditions have been proposed, from major changes in the ocean circulation and intensification of regional upwelling, to increased delivery of nutrients to the oceans and intensification of the Late Miocene Asian monsoon. We investigated the Late Miocene Biogenic Bloom at ODP Site 1085 (Cape Basin, southeast Atlantic Ocean, 1713 m water depth) and at IODP Site U1506 (Tasman Sea, southwest Pacific Ocean, 1505 m water depth). For both sites we generated an integrated age model and a quantitative benthic foraminiferal record across an interval spanning from the Tortonian (Late Miocene) to the Zanclean (Early Pliocene). The analysis of benthic foraminiferal assemblages points to the identification of two intervals at both sites. The first interval contains abundant phytodetritus exploiting taxa (PET) that indicate high seasonal supply of organic carbon and well oxygenated bottom waters. The second interval is characterized by relatively low abundance of PET, and is likely associated with a steady supply of organic carbon and low oxygen conditions at the seafloor. However, the PET groups at the two sites are dominated by different species, with Globocassidulina crassa and Globocassidulina subglobosa dominating at Site U1506, and Epistominella exigua and Alabaminella weddellensis at Site 1085.

Acknowledgements: Funding from University of Padova DOR grant, CARIPARO Foundation Ph.D. scholarship, Fondazione Ing. Aldo Gini scholarship, and Spanish Ministry of Economy and Competitiveness and FEDER funds (PID2019-105537RB-I00).