Sea surface temperature and terrestrial biomarker records of the last 260 ka of core MD05-2904 from the northern South China Sea

Abstract

This paper reports high-resolution biomarker records of the last 260 ka for core MD05-2904 from the northern South China Sea (SCS). The sea surface temperature (SST) record using the U 37 k′ index reveals a minimum of 21.5°C (MIS 2) and a maximum of 28.3°C (MIS 5.5), for a temperature difference of almost 7°C, and provides the longest high-resolution U 37 k′ SST record in northern SCS. The content of odd-number long chain n-alkanes and several n-alkanes indexes such as the CPI, ACL and the C31/C27 ratio, all reveal generally higher values during the glacials and lower values during the interglacials. Terrestrial input as indicated by n-alkane content was mostly controlled by sea-level changes: During the glacials, lower sea-level exposed the continental shelf to enable rivers to transport more terrestrial materials to the slope; and the situation reverses during the interglacials. The n-alkane indexes changes reveal more n-alkanes from contemporary vegetation during glacials as a result of the proximity of the core site to the source region, while the increases in ACL and C31/C27 ratio during glacials indicate a change to more grassy vegetation. However, the highest values for CPI, ACL and the C31/C27 ratio all occurred during late MIS 3, and it was suggested that this period was characterized by a strong summer monsoon-dominated humid climate which resulted in a denser vegetation for the exposed continental shelf region.