Publication: Advances in Polar Science (APS). Antarctic Research, Vol. 3, No. 1, 17~24, June 1992
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Author: Shen Yanbin
CNARC member: Polar Research Institute of China (PRIC)
Abstract: A new lithostratigraphic unit - Half Three Point Formation is determined on an inlet (62°13´40S, 58°59´01W) near Half Three Point of Fildes Peninsula of King George Island, South Shetland Islands. This formation consists of volcanic breccia, sediment - tuff, tuffaceous siltstones and mudstones about 5.5m thick. The Palynomorph assemblage is of Late Cretaceous age (Campanian - Maastrichtian). Isotopic age of the tuffites by Rb - Sr whole rock method is 71.30±0.3 Ma.
The calcite of sand - sized tuffites formed by calcitization during early diagenesis has very light δ18C value of - 26.24%,PDB, and δ13C value of -5.631%, PDB. It suggests that the calcitization is related to thermal freshwater originally. The tuffaceous mudstone contains lower B content of 48.4 ppm, corresponding to that of lacustrine mudstones. Lo 87 Sr/86 Sr ratio (0.703189-0.703320) indicates the tuffites of continental origin. Therefore, the formation may represent a lacustrine deposit under low energy and reducing environment. This is only known to define the late Late Cretaceous lacustrine sediments in Antarctica.
Key words: Late Cretaceous, Lacustrine sediment, West Antarctica
