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

Nilesh Bhatt ¹

Affiliations
1 Department of Geology, M.S. University of Baroda, Vadodara-390 002, IN

Abstract

A formal lithostratigraphic classification is suggested for the Neogene-Quaternary sediments of the Dwarka-Okha (Okhamandal) area. They are classified into three formations viz., Gaj, Dwarka, and Chaya. The Gaj Formation is divided into Ashapura Clay Member and Ranjitpur Limestone Member, and it ranges from Lower to Middle Miocene in age. The disconformably overlying Dwarka Formation is of Middle Miocene to Lower Pliocene age and divisible into three members viz., Positra Limestone, Shankhodhar Sand-Clay and Kalyanpur Limestone. The Quaternary deposits unconformably overlie this unit and are classified into Chaya Formation that consists of Okha Shell Limestone and Aramda Reef Members. These are Middle to Upper Pleistocene in age.

Keywords

Lithostratigraphy, Neogene-Quaternary, Dwarka-Okha Area, Gujarat.

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Nilesh Bhatt ¹

Affiliations
1 M. S. University of Baroda Vadodara - 390 002, IN

Abstract

No Abstract.

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Uday Bhonde ¹, Nilesh Bhatt ²

Affiliations
1 Institute of Seismological Research, Raisan, Gandhinagar - 382 009, IN
2 Department of Geology, The M. S. University of Baroda, Vadodara - 390 002, IN

Abstract

Coastal cliffs and shore platforms are important geomorphic features of coastal areas of Saurashtra. These features are composed of medium to coarse grained carbonate sand and are designated as "Miliolitic limestones" that range in age from Middle to Late Pleistocene. Significant jointing has been observed in the Middle Pleistocene Miliolite Formation as well as in the younger shell limestone that comprises Chaya Formation of Late Pleistocene. Along with NE-SW trend which is the direction of maximum horizontal compressive stress [S_Hmax] for Indian sub-continent, other trends recorded are NNE-SSW, N-S, NW-SE and E-W. When compared with other regional studies, neotectonic episode in Saurashtra peninsula appears to be younger than at least 125ky. The present study on joint sets also indicates that they are important to understand stresses associated with anticlockwise rotation of the Indian plate.

Keywords

Quaternary, Carbonate Deposits, Joints, Neotectonics, Saurashtra.

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Jayendra Lakhmapurkar ¹, Nilesh Bhatt ²

Affiliations
1 Gujarat Ecology Society, 3, Synergy House, Subhanpura, Vadodara - 390 023, IN
2 Department of Geology, M.S. University of Baroda, Vadodara - 390 002, IN

Abstract

Water chemistry, sediment texture, clay mineralogy and foraminiferal contents from the bottom of Meda creek were studied to assess the geo-environmental status of the creek. Water quality data for three seasons suggests domination of marine environment as pH remained above 8 and salinity above 35‰ throughout. Clay dominate the bottom sediments, except near mouth. Montmorillonite, illite and kaolinite are the major clay minerals in the sediments. In absence of any source rock in the catchment of the Meda creek, the presence of illite and kaolinite indicates their transportation and depositions from near coastal waters during high tides. Ammonia sp. is the most dominating foraminifera. Reworked forms as well as angular asymmetric forms of foraminifera were dominant in clay rich areas of the creek.

Keywords

Geo-Environment, Clay Minerals, Foraminifera, Creek, Saurashtra, Gujarat.

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Nilesh Bhatt ¹, M. P. Patel ¹

Affiliations
1 Department of Geology, The M.S. University of Baroda, Vadodara-390 002, IN

Abstract

The high energy coastal segment between Okha and Diu in Western Saurashtra is characterised by typical kind of raised bioclastic shore deposits. These occur up to 15 m (max.) above present day mean sea level and about 5 km inland. Variously described as "coast fringing rocks", "Chaya Formation", "ancient beach rocks", "shell limestones", etc., these possess poorly sorted allochems and lithic fragments of coarse sand to gravel size, mostly cemented by aragonitic micrite and occasionally fibrous aragonitic and high magnesian calcite, their pores being infilled by second generation of low magnesian sparry calcite cement. On the western coast of Saurashtra, they underlie coastal dunes and sheets of rniliolitic limestone and form gently seaward dipping sheets and their surfacial exposures are encountered southward only up to Kadwar, near Diu. However, they occur at the base of deep quarries of miliolitic limestone between Kadwar and Mahuva. Looking at the available reliable Th²³⁰/U²³⁴ and ESR dates of fossil shells from these deposits, they represent a higher sea level during the oxygen-isotope sub-stage 5e. On the South Saurashtra coast, the high coastal cliffs of miliolitic limestone exhibit presence of raised shore platforms and notches which may be related to this high sea after considering the influence of tectonism.

Keywords

Sedimentology, Quaternary, Bioclastic Sediments, Sea-Level, Saurashtra.

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Nilesh Bhatt ¹, M. P. Patel ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Vadodara - 390 002, IN

Abstract

The miliolites of Saurashtra Peninsula represent reworked bioclastic sand accumulations under the varying palaeoclimatic conditions during the Late Quaternary period. Their origin, whether marine or aeolian, forms a matter of controversy. These rocks comprise medium to fine grained allochems along with minor amount of detrital grains cemented together by non-ferroan, low magnesian sparry calcite cement exhibiting various ultrastructures. The intragranular porosity, geopetal infilling, dripstone-drapstone, meniscus and dogtoothspar cements suggest vadose condition while the presence of isopacholls rim and blocky void filling cements indicate their formation in phreatic freshwater environment.

Keywords

Sedimentary Petrology, Miliolite, Freshwater Diagenesis, Quaternary, Saurashtra.

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S. P. Prizomwala ¹, S. B. Shukla ¹, Nilesh Bhatt ¹

Affiliations
1 Department of Geology, M.S. University of Baroda, Vadodara - 390 002, IN

Abstract

Indus is one of the major sources of sediments to the Gulf of Kachchh. Yet only its <63 micron fraction is studied in detail with regards to the offshore current dynamics. Hence here we present our study on characteristic signature of the Indus sediment load (i.e. mica minerals) in >63 micron size fraction along the coast of Gulf of Kachchh. The spatial distribution of mica minerals along the Gulf of Kachchh coast was studied which showed in general decreasing trend as we move along the northern and southern coast of the Gulf of Kachchh but, an increase in amount near the southern mouth at Okha. The study shows that the earlier proposed tidal barrier is ineffective in restricting movement of mica across the mouth of the gulf due to its characteristic transport mechanism. Also the presence of mudflats along the gulf of Kachchh coast plays a vital role as sediment receptors in the active sediment transport processes and mica minerals prove to be a promising simple tracer in studying the Indus born sediments in the region.

Keywords

Mica Minerals, Sediment Pathways, River Indus, Gulf of Kachchh.

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