High Resolution Oxygen Isotope Straigraphy for the Last 150,000 Years in the Southern South China Sea:Core MD972151

Abstract

A detailed high-resolution oxygen isotope stratigraphy over the last two glacial-interglacial cycles in the southern South China Sea is presented, based upon analysis of Globigerinoides sacculifer (planktic foraminifera) in Core MD972151. Major characteristic isotopic events were identified and correlated to the standard SPECMAP chronology. In addition, radiocarbon dating and a few biostratigraphic, geomagnetic and tephrochronologic markers were employed to enhance the reliability and resolution of the age model. The tephra layer of the Toba Eruption at 71 ka helps to another the boundary of Stages 5/4, and provides a yardstick correlating to the cold period between interstadials 19 and 20 identified in the GISP2 Greenland ice core. The last appearance of pink Globigerinoides rubber and the Blake magnetic polarity event in the lower part of the core helped us to locate the transition of Stage 6/5e. Our high-resolution oxygen isotope stratigraphy, however, indicates that the age of the Blake magnetic reversal occurred during the Stage 6/5e transition instead after the warmth peak of the isotopic event 5e.

The resulting age model shows that the 26.54 m sequence from Core MD972151 provides a continuous record from 153 to 0.94 ka, with sedimentation rates varying between 5.6 and 78 cm/kyr. The temporal resolution of the isotopic record is about 60 -150 years per sample for the upper part of the core and 250 years for the lower part, respectively.

Read 1092 times