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

S. D. Singh ¹

Affiliations
1 Palaeontology Laboratory, KDM Institute of Petroleum Exploration, Oil and Natural Gas Corporation Limited, Kaulagarh Road, Dehra Dun - 248 195, IN

Abstract

Petrographic attributes of intertrappean beds exposed at four localities in Mumbai, one each at Malabar and Worli Hills and two at the Amboli quarry, Jogeshwari are studied in detail. Microfacies of vitric tuff, lithic tuff and black carbonaceous shale have been identified, which differ from their counterparts in other intertrappean localities of peninsular India in having a significant amount of pyroclastics. Bulk XRD anatyses of intertrappean beds of Malabar Hill show similar mineral assemblage in tuffs as well as black carbonaceous shales pointing towards the same provenance for these beds. Further, the XRD analysis of the clay fraction of these samples reaffirms their pyroclastic nature, the pyroclasts being reworked in most cases.

Keywords

Mineralogy, Clay Minerals, Tuffs, Carbonaceous Shale, Intertrappean Beds, Deccan Trap, Mumbai, Maharashtra.

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S. D. Singh ¹, D. N. S. Raju ²

Affiliations
1 Paleontology Laboratory, Geology Division, K.D.M. Institute of Petroleum Exploration, Oil and Natural Gas Corporation Ltd., Kaulagarh Road, Dehradun-248195, IN
2 10, Siddhartha Enclave, General Mahadev Singh Road, Dehradun - 248 001, IN

Abstract

Biometric study is carried out on a rich assemblage of the genus Heterostegina from the basal part of the holostratotype of the Waiorian stage, Kachchh. The assemblage is from a level between the last occurrence level of Nummulites fichteli Michelotti and the first appearance of miogypsinids and Globigerinoides primordills Blow and Banner and can be dated as Chattian. The assemblage consists of a single homogenous population of Heterostegina (Vlerkina) borneensis Van der Vlerk. Published data together with our present results suggest that (1) there is an overall drop in the mean value of the size of the protoconch from Heterostegina (Vlerkinu) in the Chattian to Hererostegina (Heterostegina) in the Middle Miocene and, thereafter, a slight increase in protoconch size in the Recent; (2) the mean number of operculine chambers increases from the Chattian to the Burdigalian and (3) the mean height of the first whorl drops gradually from the Chattian to the Recent.

Keywords

Heterostegina Foraminifera, Biometry, Evolution, Chattian, Kachchh, Gujarat.

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Anil Bhandari ¹, S. D. Singh ¹

Affiliations
1 Paleontology Laboratory, Geology Division, K.D.M.I.P.E., Oil and Natural Gas Corporation Limited, Dehra Dun - 248 195, Uttranchal, IN

Abstract

A total of 24 ostracode species belonging to 14 genera are recorded from the Krishna River estuary and Gautami-Godavari estuary. The study reveals that the upper estuary is dominated by thin shelled Hemicytheridea andhraensis (Annapurna and Rama Sarma) and few fresh water ostracodes having low frequency (05) and diversity (2-3). The lower estuary ostracodes have some influence of marine ostracodes and comparatively high frequency (50-60) and diversity (08). Ostracodes recorded from the lower estuary are represented by Kallingella mckenziei Jain, Neosinocythere dekrooni (Kingma), Tanella gracilis Kingma, Neomonoceratina iniqua (Brady), Phlycetenophora orientalis (Brady) along with Hemicytheridea andhraensis (Annapurna and Rama Sarma). This study will be helpful in understanding and recognizing palea subenvironment and thus helpful in developing precise pafeodepositonal model which will give further lead to hydrocarbon exploration.

Keywords

Recent Ostracoda, Deltaic Subenvironment, Inner Shelf, East Coast, India.

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