Sedimentation history of basal part of the Gondwana Basin: A case study in Yellandu, Khammam District, Telangana Debapriya Adhikary* 1 and Sebabrata Das* 2 State Unit: Andhra Pradesh, Geological Survey of India, Hyderabad-500068 2. Geological Survey of India, State Unit: Arunahcal Pradesh, North Eastern Region, Itanagar, India Corresponding author E-mail: *debapriya.adhikary@gmail.com and sebabratadas@hotmail.com Abstract: The Gondwana sediments which show a glacio-fluvial sedimentation history in and around Yellandu area, are represented by fine grained greenish coloured sandstone belonging to Talchir Formation. The Talchir conglomerate and greenish sandstone occur in the basal part of the Gondwana Basin. The basal part of Talchir contains boulders of Pakhal metasediments and granitoids which form the basement for the Basin. Clasts of deformed Pakhal phyllites recorded are reworked in the basal part of Talchir sequence. The attitude of bedding in Talchir sandstone is NW-SE dipping gently towards the NE. The present study indicates that, the Talchir sedimentation is explained by a glaciofluvial model. The unit described as ‘basal boulder bed’ in the area is actually represented by a matrix rich conglomerate with pockets of normally graded clay. The study shows glaciofluvial depositional imprints which are preserved in this part of the sedimentary succession. Further they also indicate emplacement of successive debris flows generated through remobilization of pre-existing unconsolidated sediments. Presences of boulders of different size which are well rounded to subrounded indicate the activity of sheet glacier. Subrounded fragments of Pakhal phyllites are also present in the boulder bed. Absence of any unequivocal signature of glacier origin and dominance of rounded to subrounded gravel within this matrix-rich conglomerate go against the interpretation of glacial deposit. Remobilization of the pre-existing sediments in bringing about the present conglomerate appears more possible. The overall massive character and disordered distribution of gravel fraction floating within clay-rich matrix indicate the deposition of this conglomerate from cohesive debris flow. In the lensoid pocket, embedded within the conglomerate, distribution type normal grading is observed within the silty-clay layers which indicate an inflow differentiation of grains, likely to take place within turbidity currents as demonstrated by Middleton (1966a, 1966b, 1967). The depositional imprints