A late Quaternary planktonic foraminiferal oxygen isotope record of the Banda Sea: Chronostratigraphy, orbital forcing, and paleoceanographic implications

A detailed oxygen isotope time-scale based on planktonic foraminifera. Globigerinoides sacculifer at site MD012380 in the Banda Sea was established for the past 820 kyrs by correlating the record to the astronomically tuned benthic oxygen isotope chronology of MD972143. Ages for marine isotope stratigraphic (MIS) events from 2.0 back to 21.1 were designated for this western tropical Pacific record. Spectral analysis of the δ¹⁸O time-series reveals distinct periodicities of 100, 41, and 23 kyrs, indicating strong orbital forcing, yet the power of each band varies through time. The time-series of three other paleo-proxies, namely, coarse fraction (CF), lightness of sediments and δ¹³C of Globigerinoides sacculifer, were subjected to cross-spectral analyses against the oxygen isotope record. The Mid-Brunhes (MIS 13-10,535-333 ka) divides the record into two time domains characterized by different spectral behaviors. Before the Mid-Brunhes, the analyzed proxies show relatively stronger powers at the 41-kyr band, and the coherence among various proxies is relatively high. After the Mid-Brunhes, 100-kyr periodicity becomes to dominate the δ¹⁸O and coarse fraction records while coherence among the various proxies becomes weaker. The spectral behaviors of the various paleo-proxies appear to vary through the late Quaternary and are fundamentally changed by the Mid-Brunhes event, suggesting the existence of an ever changing, internally complicated system of the Banda Sea under the influence of orbital forcing during the last 820 kyrs.