The Talya Conglomerate: an Archean (∼2.7 Ga) Glaciomarine formation, Western Dharwar Craton, Southern India

Abstract

The ∼2700 Ma Talya Conglomerate is Comprised of 15 Diamictites (i.e. Matrix-supported Conglomerates) Interbedded with Mudstone and Sandstone Units, and is Interpreted as a Glaciomarine Deposit. the Entire Thickness of This Conglomeratic Member within the Vanivilas formation, the Lowest formation of the Chitradurga Group of the Neoarchean Dharwar Supe Rgroup, is Exposed in a 543 M-thick Measured Section. it is in a Sub-vertical Attitude, is Highly Sheared, and has Undergone Greenschist Facies Metamorphism. the Diamictites had an Original Matrix of Laminated Mud/Silt and Fine Sand. while Including Diamictites Throughout, the Talya is a Fining-upward Sequence with Intercalated Sandstones Dominant in its Lower Portion and Mudstones Dominant in its Upper Portion. we Interpret that the Talya Conglomerate was Deposited in a Marine Environment, with Diamictites Composed of Ice-rafted Detritus (ird) Deposited from Icebergs Calved from Tidewater Glacier Tongues And/or possibly from Ice Shelves. in these 'rainout Diamictites' the Larger Clasts were Dropped into Finegrained Bottom Sediment Deposited by Sediment Plumes and Currents. the Source Ice Sheet was Located to the West and Southwest on a Land Mass that Included the Older than 2720 Ma Bababudan Group of Quartzites and Mafic Volcanics and Older than 3000 Ma Basement of Granitic/gneissic Rocks. Application of Walther's Law Indicates that the Mudstonebearing Portion of the Talya was Deposited upon the Sandstone-bearing Portion as the Sea further Inundated the Land Mass Due to Glacial Retreat and a Decrease in Glacial Mass, thereby Resulting in the Fining- upward Nature of the Talya Conglome Rate. we also Interpret the Lower Portion of the Kaldurga Conglomerate, Located 50-75 Km to the Southwest of the Talya, to be Equivalent with the Talya. the Kaldurga Contains mostly Granitic Basement Detritus, perhaps Exposed Due to Basement Uplift Related to Isostatic Rebound Caused by Glacial Melting or Due to Tectonism Related to Westward Subduction.