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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 58 (1974)

Issue: 2. (February)

First Page: 304

Last Page: 311

Title: Sphaeroidinella dehiscens Datum and Miocene-Pliocene Boundary: GEOLOGIC NOTES

Author(s): M. S. Srinivasan (2), S. S. Srivastava (3)

Abstract:

Five planktonic foraminiferal zones can be recognized in the late Miocene to middle Pliocene of Long, Car Nicobar, and Chowra Islands, Bay of Bengal. The early Pliocene marker species Globorotalia margaritae first makes its appearance slightly above the horizon marked by the first evolutionary development of Sphaeroidinella dehiscens from its immediate ancestor Sphaeroidinellopsis subdehiscens (which marks the Zone N. 18-N. 19 boundary of Banner and Previous HitBlowTop). The first evolutionary appearance of Sphaeroidinella is a valid datum in tropical regions and marks the Miocene-Pliocene boundary. This level is stratigraphically much lower than the "S. dehiscens datum" described by Bandy in the Philippines. The important temperate Pliocene-Pleistocene forms, Globorotalia inflata, G. p ncticulata, and G. crassaformis are absent, presumably because of the tropical conditions in the Bay of Bengal.

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