Goridwana zyxwvutsrqponm Reseurcli, zyxwvutsrqpo I/: 6, No. 4, zyxwvutsrqpo pp. 573-583. zyxwvutsr 0 2003 Inteinutional Association for- Gondwana Research, Japan. ISSN: 1342-937X Deformation Pattern in the I<urnool and Nallarnalai Groups in the Northeastern Part (Palnad Area) of the Cuddapah Basin, South India and its Implication on Rodinia/Gondwana Tectonics Dilip Saha and Sukanya Chakraborty Geological Studies Unit, Indian Statistical lnstitiitc, 203 13. T. Road, Kolknta zyxwv - 700 108, India, E-mail: dsahaOisical.nc.iiz (Mantiscript received Azrgiist 13, 2002; accepted Febriiary 5,2003) zyxwvu Abstract Thc Proterozoic basins of India adjoining the Eastern Ghats Granulitc Bclt (EGGB) in eastern and southcrn India contain both Mcsprotcrozoic and Ncoprotcrozoic successions. Thc inti-acratonic set-up and contractional dcformation of thc Neoprotcrozoic succcssions in the Palancl sub-basin in the northeastern part of Cuddapah basin and similar crustal shortcning in cont~mporanco~~ successions lying west of thc EGGB and Ncllorc Schist Belt (NSB) arc considcrcd in relation to the proposcd gcodynamic evolution of thc the Rodinia and Gondwana supercontincnts. Tectonic shortening in the Palnad sub-basin (northcast Cuddapah), partitioncd into top-to-wcstnorthwcst thrust shcar, flexural folds and clcavagc dcvclopment undcr overall E-W contraction, suggests forcland stylc contincntal shortening within an intracratonic sct-up. A thrust shect containing the Nallamalai rocks and overlying thc Kurnool rocks in thc northeastcrn part of Palnad sub-basin cxhibits carly tight to isoclinal folds and slaty (phyllitic) clcavage, which can bc correlated with carly Mcsoprotcrozoic dcformation structurcs in the northern Nallamalai Fold Bclt (NFB). NNE-SSW trending folds and cleavage affcct thc Kurnool Group and ovcrprint earlier structurcs in the thrust shect. Thrusting of the Nallamalai rocks and the latcr structures may havc bccn related to convergence of the Eastcrn Ghats tcrranc and the East-Dhanvar-Bastar craton during Early Ncoproterozoic (Greenvillian) and/or latcr rejuvcnation relatcd to Pan-African amalgamation of East and Wcst Gondwana. . . . , ... . Key words: Cuddapah Basin, intracratonic fold-and-thrust belt, Ncoproterozoic, Ndore Schist Belt, South India. Introduction Recent geological evidence and analysis have led to the hypothesis of Proterozoic supercontinents, e.g., Columbia, Rodinia, which are supposed to have evolved through cyclic fragmentation and amalgamation of a number of continental fragments belonging to the erstwhile East Gondwana including India (e.g., Dalziel, 1991; Hoffman, 1991; Moores, 1991; Rogers, 1996; Yoshida et al., 1996; Unrug, 1997, Rogers and Santosh, 2002). Although multiple lines of data and arguments are put forward to support the Columbia or the Rodinia hypothesis, works that take into account the development of intracratonic basins in relation to these supercontinent assembly and breakup are not many (Chaudhuri et al., 2002). The present contribution deals with tectonic shortening of the Cuddapah Basin, other Proterozoic basins adjoining the EGGB, in relation to possible amalgamation of India and other East Gondwana fragments within the broad framework of geodynamic evolution of continental fragments sundered from the Rodinia and their subsequent assembly into the Gondwana. A number of intracratonic basins, namely the Chattisgarh Basin and its southern extension in Khariar and Ampani, the Indravati Basin, the Pranhita-Godavari (PG) Basin and the Cuddapah Basin, occur in proxirnity and to the west of the Eastern Ghats Granulite belt (EGGB) and the Nellore Schist Belt (NSB) in the southern cratonic province of India (Fig. 1). Mesoproterozoic to Neoproterozoic sedimentary sequences, roughly varying in thickness from 0.5 km to 8 km, occur in these basins. The Cuddapah Basin has late Paleoproterozoic (ca. 1800 Ma) sediments as well (Bhaskar Rao et al., 1995). Earlier works have assigned Neoproterozoic age to the Kurnool Group in the Cuddapah Basin, the Sullavai Group in the PG Basin and part of the Indravati and Chattisgarh Groups zy Gondw ana zy , Research zy GR