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

M. G. Hardas ¹, S. S. Merh ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Baroda, IN

Abstract

No Abstract.

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Geeta Desai ¹, M. G. Hardas ², M. P. Patel ¹, S. S. Merh ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Baroda 390002, IN
2 Regional Laboratories, Oil & Natural Gas Commission, Baroda 390009, IN

Abstract

Miliolites occur within the Kutch highlands as thin horizontal sheets occupying topographic depressions or as obstacle dunes resting against the slopes of big hills. Sheet deposits of the low-lying ground, reveal a marine origin and are seen to consist of pellets and microfossils embedded in a micritic to fine sparry matrix. These valley-fill sheet deposits are characterised by a faunal assemblage typical of warm, clear, shallow, carbonate-rich sea, where terrigenous influx was poor. On the other hand, the obstacle dunes typically comprise aeolinites and appear to have developed during the regression of the sea, the strong winds having lifted the exposed carbonate sands and dumped them against the nearby hillsides. The higher strand line indicated by these marine miliolites could be related to one of the Quaternary transgressions.

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M. G. Hardas ¹, D. C. Srivastava ¹, M. M. Maindarkar ¹

Affiliations
1 Regional Laboratories, Oil and Natural Gas Commission, Baroda 390009, IN

Abstract

The limestones of Dadhar Formation (Lower Oligocene) in the Anklesvar oil field of Cambay basin, provides a typical example of erosional transgression. Interbedded with grey, fossiliferous shales and fine grained sandstones, these carbonate layers have been found to be biomicrudites comprising foraminiferal shells, glauconite, terrigenous sand, silt and clay, microspar patches and development of pseudospar in fossil shells. The above assemblage, especially the glauconite and recrystallized microspar and pseudospar, typically indicates a transgressive marine environment, characterised by calm, weak and shortlived currents. Most earlier workers have invoked a regressive phase for the deposition of this limestone but recent microfaunal studies and the salinity data point to an inner neritic environment transgressive phase.

The petrography provides evidences to reveal a marine environment of shallow tidal sea, wherein the marine incursion must have been characterised by tidal effects and reworking of the older sediments.

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G. Lahiri ¹, M. G. Hardas ²

Affiliations
1 ONGC-Schlumberger Wireline Research Centre, New Delhi - 110 003, IN
2 ONGC, Ankleshwar Project, Ankleshwar, Gujarat - 393 010, IS

Abstract

The Cretaceous Sandstones in Nannilam Field of Cauvery Basin, have a few significant hydrocarbon reservoirs. In general, Upper Creataceous Sandstones are good quality reservoirs with mostly intergranular and interconnected dissolution pores while Lower Cretaceous Sandstones are low-quality reservoirs with mostlymicropores and a few interconnected pores.

Keywords

Diagenesis, Marine Environment, Hydrocarbon, Cauvery Basin.

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