| Summary: | ABSTRACT The early–middle Miocene represents a key step in the Cenozoic global climate evolution. It is characterized by the Middle Miocene Climatic Optimum (MMCO, 17 -15 Ma), followed by a thermal decrease during the Middle Miocene Climate Transition (MMCT, 15 - 14 Ma) culminating in the marked Mi3b cooling event at 13.8 Ma. A high-resolution (≈20 kyr) quantitative planktonic foraminiferal analysis was carried out on equatorial and (sub)tropical Atlantic Ocean sedimentary successions (respectively, ODP Leg 154 Site 925 and ODP Leg 208 Site 1264) from about 18 to about 14 Ma, not available yet for low latitudes. These sites were selected for their almost continuous successions, good preservation of foraminiferal assemblages and age model obtained through astronomical calibration. For each selected sample 200-300 specimens of planktonic foraminifera were classified at supraspecific and specific level (about 56 species) and counted to elaborate abundance curves against meter composite depth (mcd) and/or age. Carbonate dissolution, diversity, surface paleotemperature and paleoproductivity and water masses stratification indices (existing in literature or elaborated for the studied time interval) were plotted along the stratigraphic record and correlated with abundance curves. The obtained results could contribute to improve the recent biostratigraphic schemes for (sub)tropical latitudes (Wade et al., 2011 modified by Berggren et al., 2018) through a more accurate positioning of the biozonal events (e.g. T of Catapsydrax dissimilis, B of Globorotalia praemenardii, B of Orbulina suturalis; for both site) previously defined in Shipboard Scientific Party (Pearson & Chaisson, 1997 for Site 925; Zachos et al., 2004 for Site 1264) and additional events identification (e.g. random to sinistral coiling change of Paragloborotalia siakensis at Site 925; Tc of Globorotalia zealandica, B of Globorotalia miozea, AB/AE of P. siakensis and Parabloborotalia bella at Site 1264). Moreover, this study highlighted the rarity (and ...
|
|---|