Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Kapesa Lokho ¹, D. S. N. Raju ²

Affiliations
1 Wadia Institute of Himalayan Geology, 33- GMS Road, Dehradun- 248001, IN
2 10 Siddharth Enclave, GMS Road, Dehradun- 248001, IN

Abstract

A small but varied assemblage of planktonic and benthic foraminifers comprising at least six genera and seven species is documented from the Upper Bhubhan Formation exposed at Thuampui in Aizawl District of Mizoram (NE India). The fossils from Thuampui are generally poorly preserved and some are even deformed, nevertheless they are important for determination of age and paleobathymetry. Based on this foraminiferal assemblage an early Middle Miocene age equivalent to planktonic foraminiferal zones N8-N9 and a paleobathymetry of 50 m is suggested for the fossiliferous Upper Bhubhan Formation at Thuampui of Mizoram.

Keywords

Bhubhan Formation, Early Middle Miocene, Foraminifera, Mizoram.

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Kapesa Lokho ¹, D. S. N. Raju ², R. J. Azmi ¹

Affiliations
1 Wadia Institute of Himalayan Geology, 33 GMS Road, Dehra Dun - 248 001, IN
2 MSR Residency, Pragathi Marg, JN Road, Rajahmundry - 53 3103, IN

Abstract

Planktic and benthic foraminifera including uvigerinids are documented from the Upper Bhuban Formation, exposed at Thingdawl village, Kolasib district, Mizoram. The foraminiferal assemblage is poorly preserved and consists of index fossils useful for precise biochronology and interpretation of the depositional environment. A total of ten benthic and six planktic foraminiferal species are described. Six species belong to the genus Uvigerina, four to Ammonia, one species each of Globorotalia, Globigerinoides, Clavatorella, Praeorbulina and two species of the genus Orbulina. Based on lithological and foraminiferal assemblage, middle neritic to upper part of outer neritic paleobathymetry is inferred for the deposition of this part of the Upper Bhuban Formation. The foraminiferal assemblage suggests late Early Miocene to early Middle Miocene, (∼16 Ma) equivalent to planktic foraminiferal zones N8-N9 for the Upper Bhuban Formation.

Keywords

Bhuban Formation, Miocene, Uvigerinids, Foraminifera, Assam-Arakan Basin, Mizoram.

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