Abstract:

Rapid isotopic variation affected by Late Cretaceous greenhouse is of globe implication, and can be used as proxy of climate change in the Earths history. In continental sedimentary system, relatively continuous paleoclimate signal is recorded in lacustrine sediments. It is an ideal record to recover highresolution paleoenvironment and paleoclimate changes. The Songliao lacustrine basin is a large Cretaceous sedimentary basin. A coring program, the“Cretaceous Continental Scientific Drilling Programme of China (SK1)”, was initiated to the study of Cretaceous climate change. Under this programme, an ambitious effort is now underway to develop an oxygen and carbon isotopic record for a nearly complete Cretaceous lacustrine section in the Songliao basin to reveal paleoclimate change in innercontinental area. Bulk samples were normally used to the Cretaceous stable isotope analysis. The compositions of terrestrial stable isotopes are complicated and can be affected by various factors. The present authors attempt to select ostracod carapaces as analytical materials. As a result, ostracods were handpicked from samples collected from drill cores. After removing them from rock matrix, the ostracod carapaces, matrix and filling materials were then visually examined for possible secondary calcite, such as sparry calcite, respectively. The result indicates that ostracod carapaces are avoided from secondary calcite and /or diagenesis. They are reliable materials for the isotopic study. Specifically, we demonstrate that the carbon and oxygen isotopes recorded in the ostracod carapaces of the Songliao basin seemingly track the corresponding contemporaneous isotopic records during Late Cretaceous. The isotopic curves will be the criterion of terrestrial isotopic succession in China after detailed study.

Key words: SK1, ostracod carapace, stable isotope;