极地研究

极地研究 ›› 1992, Vol. 3 ›› Issue (1-English): 17-24.

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A NONMARINE LATE CRETACEOUS DEPOSITIONAL UNIT ON KING GEORGE ISLAND, WEST ANTARCTICA

Shen Yanbin   

  1. Nanjing Institute of Geology and Palaeontology, Academia Sinica, Nanjing 210008, China
  • 出版日期:1942-03-30 发布日期:1942-03-30
  • 通讯作者: Shen Yanbin
  • 基金资助:

    The project was supported by State Antarctic Committee and National Natural Science Foundation of China.

A NONMARINE LATE CRETACEOUS DEPOSITIONAL UNIT ON KING GEORGE ISLAND, WEST ANTARCTICA

Shen Yanbin   

  1. Nanjing Institute of Geology and Palaeontology, Academia Sinica, Nanjing 210008, China
  • Online:1942-03-30 Published:1942-03-30
  • Contact: Shen Yanbin
  • Supported by:

    The project was supported by State Antarctic Committee and National Natural Science Foundation of China.

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摘要：

A new lithostratigraphic unit - Half Three Point Formation is determined on an inlet (62°13'40"S, 58°59'01"W) 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. 130 to 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. Low87 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.

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关键词: Late Cretaceous, Lacustrine sediment, West Antarctica

Abstract:

A new lithostratigraphic unit - Half Three Point Formation is determined on an inlet (62°13'40"S, 58°59'01"W) 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. 130 to 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. Low87 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