Tidal Flat Sedimentation in Bairenkonda Formation of the Tirumala Hills, Southwestern Part of the Cuddapah Basin, Andhra
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Tidal Flat Sedimentation in Bairenkonda Formation of the Tirumala Hills, Southwestern Part of the Cuddapah Basin, Andhra Pradesh G. Lakshminarayana1,2*, D. Vijay Kumar1, S. Kalyan Kumar1 and R. Vaidyanadhan3 1
Midwest Granite Private Limited, Road No.-12, Banjara Hills, Hyderabad – 500 034, India Director (Retd), Geological Survey of India 3 Professor (Retd), Andhra University, Visakhapatnam. *E-mail: [email protected] 2
ABSTRACT Siliciclastic sediment succession of the Bairenkonda Formation of the Proterozoic Cuddapah Supergroup overlies the granitegneiss of the east Dharwar craton along a nonconformity in the Tirumala hills. Basin fill sediments are now classified in ascending order into three lithofacies assemblages namely; lower crossstratified sandstone (CSS); middle sand-dominated heterolithic (MH) and upper shale-dominated heterolithic (UH) associations. Paleocurrent was towards east in CSS; bi-directional in MH and UH. Provenance was in west. Lithofacies attributes have indicated that the CSS was deposited along foreshore/supratidal environment where sedimentation had taken place under the combined influence of waves, storms and tides. The succeeding MH assemblage represents deposition in channels and distributaries over sandy intertidal flats. The upper mud dominated heterolithic assemblage (UH) was deposited in mixed intertidal to subtidal flats. Accordingly, the depositional milieu contemplated for the Bairenkonda Formation is tidal flat in shallow marine environment. Siliciclastic sediments thus deposited were uplifted due to basin inversion to form the mighty Tirumala hills in southwestern part of the Cuddapah basin, Andhra Pradesh. INTRODUCTION The Proterozoic sedimentary basins in the Indian sub-continent are mainly of intra continental/epicontinental type covering more than one fifth of the Precambrian exposures in the Peninsula shield area. Sediments of these basins display several peculiarities which are believed to have been deposited in an epicontinental sea that once flooded the Indian subcontinent (Radhakrishna, 1987; Kale and Phansalkar, 1991; Singh, 1980; Ramakrishnan and Vaidyanadhan, 2010). Among these, the Cuddapah basin occupies a place of preeminence for its long-standing geological history, varied rock types, multiple stages of basin development and rich mineral deposits (Geological Survey of India, 1981). Since the publication of the landmark memoir on the Cuddapah basin by King (1871), voluminous literature has accrued on its multi-faceted aspects like stratigraphic framework, structure, tectonics, geochronology, geophysical aspects and mineral deposits, succinctly summed up by Nagaraja Rao et al., (1987); bench mark papers on the Cuddapah basin have been compiled by Lakshminarayana (2005). Sedimentary facies and depositional environments of the Cuddapah basin sediments on modern lines have received sporadic attention up to mid-1990’s with an exception being the description of the sedimentary structures in the Tirumala sandstones by Vaidyanadhan, (1957), algal structures in l
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