First Occurrence of Planktonic Foraminiferal Species Boliella Adamsii As a Marker for the Pleistocene-Holocene Boundary in the Sea Around Sumba Island

The expensive cost of Accelerator Mass Spectrometry radiocarbon dating (AMS 14C), the main tool for geochronology in Late Pleistocene-Holocene paleoclimate and paleoceanography study using marine sediment cores, hinders Indonesian researchers to produce competing research outputs. The first occurrences of planktonic foraminiferal species which have been applied as Pleistocene-Holocene Boundary markers in previous Quarternary marine sediment studies in the Indonesian region need to be confirmed as these species might actually occur since the Late Pleistocene. Quantitative foraminifera determination and oxygen isotope (δ18O) analysis of planktonic foraminiferal species Globigerinoides (Gs.) ruber have been carried out in marine sediment cores ST10 (off south Sumba) and ST14 (Sumba strait). δ18O of Gs. ruber was correlated to North Greenland Ice Core Project (NGRIP) Greenland Ice Core Chronology 2005 (GICC05) δ18O to determine the depth of the Pleistocene-Holocene Boundary (11653 BP) in core ST10 and ST14. Pleistocene-Holocene Boundary depth in core ST10 (31 cm) and ST14 (28 cm) are nearly coeval with the First occurrence (FO) of planktonic foraminifera Boliella adamsii, which at 34-35 cm depth interval in core ST10 and at 26-27 cm depth interval in core ST14. This indicated the practicality of Boliella adamsii FO as a Pleistocene-Holocene Boundary marker in the sea around Sumba Island, in case radiocarbon ages and proper planktonic foraminiferal δ18O data are not available. Future studies using a similar method in other Indonesian regions are needed to confirm the practicality of Boliella adamsii FO as a Pleistocene-Holocene Boundary marker in the Indonesian region.