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M. R. G. Sayyed ¹, A. M. Patwardhan ¹

Affiliations
1 Department of Geology, University of Poona, Pune 411 007, IN

Abstract

Upper Kamthi sandstones are distinct being unimodal, less feldspathic, texturally more mature with a dominant ferruginous cement when compared with the Lower and Middle Kamthi sandstones which are bimodal, feldspathic with abundant carbonate cement. The bimodality and textural inversion in the latter is attributed to their derivation from both metasedimentary and plutonic sources. This is also reflected in the erratic distribution of Al₂O₃ total iron and Na₂O contents. The Yerrapalli sandstones are petrographically not very different from the Lower and Middle Kamthi sandstones, but show finer grained feldspar, abundant carbonate cement and lime pellets. The Bhimaram sand'stones, however, show lesser carbonate content and are characterized by the presence of pyrite and ferruginous cement. In general, the Yerrapalli and Bhimaram sandstones show a greater mineralogical and textural maturity than the Lower and Middle Kamthi units. The distribution of CaO shows a maxima in. the middle portion of the Lower Maleri sequence, other major elements donot show any systematic variation.

Keywords

Gondwana Pranhita - Godavari Basin, Kamthi Maleri Fm.

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M. R. G. Sayyed ¹

Affiliations
1 Department of Geology, Poona College, Camp, Pune-411001, IN

Abstract

The Gondwana sediments from the Pranhita-Godavari valley were analysed for major elements and some petrographical characters to find out the nature of the source of rocks, their palaeo weatbering and the palaeoclimatic conditions. The results of this study indicate that source rocks were mainly granitic in composition which had undergone K-metasomatism. Most of the major elements show large fractionation and mobilisation during weathering and transport while the intensity of weathering was highly variable under humid to subhumid climatic conditions.

Keywords

Geochemistry, Palaeoclimate, Gondwana, Pranhita-Godavari Valley, Andhra Pradesh.

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M. R. G. Sayyed ¹

Affiliations
1 Dept. of Geology, Poona College, Camp, Pune-411 001, IN

Abstract

The Gondwana sandstones from the present area of study, are studied with the help of geochemical discriminating parameters. Most of these parameters suggest a 'Passive Margin setting for the deposition of these sandstones. Excepting Upper Barakar and Upper Kamthi sandstones, other sandstones are chemically immature. These sandstones were deposited in plate interior or in the intracratonic basin and in general the basin of deposition could have been largely fluctuating.

Keywords

Gondwana, Geochemistry, Sedimentology, Pranhita-Godavari Valley, Andhra Pradesh.

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