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

S. M. Casshyap ¹, M. Aslam ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh - 202002, IN

Abstract

An earthy brown, cross-bedded, channel sandstone body overlying a thinly bedded sequence of white sandstone and red shale of the Surajdeval Formation (Iower-Cretaceous) stands out as a low-lying flat-topped escarpment, about 3-4 m high and 30-60 m wide, alongside the village Dhaduka near Chotila on the Surendranagar-Rajkot highway. Plane ta ble survey brings out a sinuous pattern of the channel sandstone body longitudinally in the north-south direction all along the escarpment.

Integrated evidence from geometry, lithofacies and paleocurrents suggest that the Dhaduka sequence is an example of exhumed channel bar of delta distributary, in association with thinly-bedded coastal plain (1ongshore/tidal current) deposits.

Keywords

Sedimentology, Surajdeval Fm., Gujarat, River delta.

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M. Aslam ¹, M. Arora ², R. C. Tewari ³

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh, IN
2 Geochemistry Section, NGRI, Uppal Road, Hyderabad, IN
3 Department of Geology, D. S. College, Aligarh, IN

Abstract

Heavy mineral analysis of the Barakar Sandstone from a drill core (117 m) from the Moher-Subbasin of the Singrauli coalfield shows relative abundance of epidote, zircon and rutile in the finer (.088-.074 mm) and garnet, muscovite and staurolite in the coarser (0.177-0.149 mm) fraction. Stratigraphically, the heavy species do not exhibit marked variation in their relative abundance, though garnet forms the bulk of the heavy crop at 94 m depth.

The study indicates that basic and acid igneous rocks, low to medium and high-grade metamorphic rocks, and metasedimentary rocks to the south and southeast of the study area, probably the Manpat ridge, supplied the bulk of the sediment debris during the early Permian Barakar times.

Keywords

Sedimentology, Barakar Sandstone, Singrauli, Gondwana.

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M. Aslam ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh-202002, IN

Abstract

A provenance study was conducted on the Mesozoic rocks of Saurashtra basin, Gujarat, in which grain size, mineralogy and petrographical features of sandstones were integrated to arrive at an consistent interpretation.

Textural parameters suggest progressive variation in that mean grain size increases from Than (0. t 98 - 0.117 mm), Surajdeval (0.257 -0.213 mm), through Ranipat (0.5 -0.378 mm), to Wadhwan (0.716 - 0.469 mm). The bulk of the sandstones demonstrate positive (+) skewness in Than and Surajdeval implying that sandstones include greater admixture of fine sediments, as aganist those of Rani pat and Wadhwan which show excess of coarse admixture. By and large, the Dhrangadhra sandstone is moderately to well sorted (σ I=0.52 - 0.84 φ).

Petrographically, three types of sandstones constitute the Dhrangadhra group of formations, namely, quartzarenite, subarkose and sublitharenite, consisting of quartz, feldspar, lithic-fragments, and mica in order of abundance. Groundmass material consists of cementing material and matrix. Heavy minerals show a preponderance of granet, zircon, tourmaline, staurolite, rutile and epidote. The study reveals a mixed provenance, comprising of acid igneous, metasedimentary rocks of the Aravalli highlands outcropping in the northeastern part of the study area.

Keywords

Sedimentary Petrology, Mesozoic, Saurashtra, Gujarat.

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M. Aslam ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh-202 002, IN

Abstract

The Early Cretaceous Ranipat Formation of Saurashtra basin is divisible into three distinct lithofacies assemblages: 1) crossbedded sandstone facies assemblage characterised by coatse to medium-grained, planar and trough crossbedded sandstone with occasional thin layers of silty mud or reactivation surfaces; 2) plane-bedded sandstone facies assemblage composed of interbedded white to clean white, medium to fine-grained sandstone, siltstone and shale with a low-diversity of shallow water trace fossils; and 3) thin-bedded sandstone and mudstone facies assemblage characterised by interbedded fine to very fine-grained sandstone, small scale planar and trough crossbedding, horizontally bedded, ripple cross-laminated, way and lenticular bedding, flaser and herringbone crossbedding with the dominant ichnogenera being Skolitbos and Ophiomorpha. These lilhofacies assemblages indicate that the Ranipat sandstone was deposited in a tidal, intertidal, and shallow subtidal shoreline environment. The mineralogy, texture, and paleocurrent data also rcveal that the sediments were brought to the Ranipat basin, largely by southwesterly streams/distributaries, with occasional dispersal and redistribution by northwesterly to northerly oriented longshore and/or tidal currents of the nearby coastal environment.

Keywords

Sedimentology, Cretaceous, Gujarat, Ranipat Formation.

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