High-resolution quantitative biostratigraphy of planktonic foraminifera across the Aquitanian/Burdigalian boundary at low latitudes

Very few high-resolution quantitative records of planktonic foraminifera are available for the Aquitanian to Burdigalian interval, especially at low latitudes. In addition, the Burdigalian GSSP has not yet been defined and the bioevent that best approximates the boundary is still debated. Provisionally, Base Helicosphaera ampliaperta (calcareous nannofossil), calibrated at 20.43 Ma (Ceara Rise), is chosen to recognize the base of Burdigalian Stage (Raffi et al., 2020). Here, the results of a high-resolution quantitative study of the planktonic foraminiferal assemblages, performed at Site 926 (ODP Leg 154, Ceara Rise, Equatorial Atlantic Ocean), are presented for the time interval from 21.4 to 17.5 Ma. Following the composite section of Site 926, astronomically tuned by Shackleton et al. (1999) and Palike et al. (2006), 142 samples were selected with a time resolution of ~30 kyr. This study provides quantitative distribution patterns of the low-latitude biostratigraphic marker species and the refinement of the stratigraphic position and age calibration of bioevents, such as Top Paragloborotalia pseudokugleri, Top common Paragloborotalia kugleri, Top P. kugleri, Top Tenuitella munda, Base Globigerinoides altiaperturus, and Base Globigerinatella sp. Catapsydrax dissimilis and randomly coiled Paragloborotalia siakensis occur in the entire studied interval. The obtained results improve the biostratigraphic resolution across the Aquitanian/Burdigalian boundary.