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

S. K. Chadha ¹

Affiliations
1 Department of Geology, Govt. G. M. Science College, Jammu (J & K), IN

Abstract

The bauxites of Jammu comprise extensive surface spreads of generally hard dense varieties with a typical knobby appearance. The bauxite unconformably overlies Upper Pre-Cambrian limestones and underlies the Nummulitic series of Eocene age. Thickness varies from 1.5 m to 9 m. Three distinct facies are recognised: pisolitic. semi-pisolitic and non-pisolitic.

The bauxites have been analysed for their mineralogical composition adopting X-ray, D.T.A., heavy mineral analyses and optical study. The pisolitic bauxites mostly contain diaspore (A1₂O₃ H₂O) and boehmite (AI₂O₃. 2H₂O), the semi-pisolitic bauxites contain, boehmite, limonite, and quartz. The non-pisolitic varieties contain kaolinite. Heavy mineral studies have shown the presence of magnetite, limonite, anatase and corundum. The source rocks appear to be limestones which weathered mitially into clay. The desilicification of the clays under tropical and sub-tropical climatic conditions gave rise to bauxite.

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S. K. Chadha ¹

Affiliations
1 Department of Geology, Jammu 180001, IN

Abstract

The ooids and peloids show diverse morphological characters, and diverse nature of their nuclei and rims. The growth, shape and size of ooids depend upon the method of sorting, formative environments and degree of sphericity they attain during rolling. The compound ooids, on the contrary, are the product of a complex method of aggregation, cementation, reworking of the grains, recementation, and finally their packing under a common envelope. The ooid bearing rocks appear to have been formed in ephemeral lagoons or playas under fluctuating conditions of formative environments with fairly high values of pH, Eh, CO₃ ionic concentration and a widely ranging hydrodynamic energy conditions of the basin.

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