Time-spatial boundaries of bioecozonations (planktonic foraminifera) in the latest Quaternary: a case study from the western South Atlantic

Planktonic foraminifera assemblages accurately record climate fluctuations that occurred during the Quaternary. These assemblage variations (frequently abundance changes) are widely used to establish bioecozones. Since climate variations are neither synchronous nor spatially homogenous, this paper assesses the application of the bioecozonations from the south Brazilian continental margin to its understudied southern extreme. To accomplish this purpose, census counts were made on core SAT-048A, retrieved from the continental slope of the southern extreme, and were compared to published records from the south Brazilian continental margin. According to the age model, the sediment core SAT-048A spans the last 42 kyr. The last reappearance of the Globorotalia menardii complex is dated for the first time in the Pelotas Basin at 8.5 ka, marking the biochronologic limit of bioecozones Y/Z. The last disappearance of Pulleniatina spp., marker of the sub-bioecozones Y2/Y1, is dated at 25.7 ka, showing an asynchronous characteristic already reported for the Caribbean and Equatorial Atlantic, meanwhile, its last reappearance, that marks the Y1B/Y1A limit, is dated at 15.5 ka, agreeing with previous studies. The Pleistocene/Holocene boundary can be recognized based on the Last Abundance Peak of the Globorotalia truncatulinoides dextral morphotype (GtdLAP), also recognized in other cores of the south Brazilian continental margin.