Chapter 8 Archaean sedimentation on the Singhbhum Craton: depositional environments of conglomerates in Jharkhand (east India)

Abstract

Archaean to Palaeoproterozoic metasediments overlie the Archaean granitoid pluton of the Singhbhum Craton in east India. Relatively little is known about the Archaean metasediments, but they comprise several conglomerates in the state of Jharkhand. Their age is most probably Mesoarchaean, possibly earliest Neoarchaean. They occur at separate localities and their exposures commonly consist of scattered patches with a limited extent. Their interrelationships are consequently poorly known. Sedimentological analysis of their structure, architecture and clast composition suggests that most of them represent individual occurrences that partly have been largely eroded away. Other occurrences must have had a limited extent from the very beginning. The various conglomerates were deposited in different environments. Some represent braided or meandering fluvial environments, whereas others seem to have been deposited by mass flows with different degrees of viscosity, possibly mainly on alluvial fans.

A hitherto unknown river type from the Archaean at Bhurkuli (Jharkhand, E India)

“…1) in the same 'belt' with Archaean conglomerates (see also Van Loon & De, 2015) is striking, regarding the clast-supported character of almost all conglomeratic beds, the local occurrence of tectonically flattened pebbles and the presence of schists that are embedding the conglomeratic units.…”

“…Reddy et al, 2002;Mohapatra et al, 2008), and even less have been investigated sedimentologically in some detail (e.g. Chatterjee & Das 2004;Van Loon et al, 2012;Van Loon & De, 2015).…”

“…As mentioned above, a section with conglomerates near Rajkharsawan was analysed sedimentologically in detail , resulting in a reconstruction of the depositional environment (a meandering river system during or shortly after a phase with volcanic activity), and Bhattacharya & Mahapatra (2008) described the Bisrampur conglomerate sedimentologically and tectonically (alluvial-fans/fan delta along the margin of a rift graben). Van Loon & De (2015) summarized some characteristics of a dozen conglomerates in the state of Jharkhand (Fig. 1).…”

Chapter 1 Precambrian basins of India: stratigraphic and tectonic context

“…Evolution of this craton is thought to reflect accretion of either arcs or an assembled arc-granitic whole batholith terrane (now preserved as the Eastern Dharwar Craton, EDC) on to the Western Dharwar Craton, which has a regionally correlatable greenstone succession, the c. 2.9-2.6 Ga Dharwar Supergroup. This craton thus displays both a widespread correlatable greenstone succession and accretionary greenstone belts which young eastwards (compare with Van Loon & De (2015) on the Singhbhum Craton greenstones), thus providing a possibly unique Archaean cratonic evolution on the global scale. Basin evolution related to tectonic shortening is also envisaged for the Proterozoic Cuddapah Basin, Cuddapah fold-thrust belt (CFTB) and the Kurnool Group succession (Matin 2015), thought to have been related to assembly of both Columbia (Cuddapah) and subsequent Rodinia (CFTB, Kurnool) supercontinents.…”

“…They define two new formations, an older distal (deeper-water) equivalent of the IOG followed unconformably by a younger deposit reflecting fault-controlled basin opening (conglomeratic) and subsequent stable shelf sedimentation. Van Loon & De (2015) critically analyse the conglomerates of Jharkhand and discuss their Archaean sedimentation patterns on the Singhbhum Craton. Both IOG and subsequent immature conglomeratic facies thus appear to have been relatively widespread on the Singhbhum Craton, thus supporting possibly broadly correlatable greenstone successions, as for example also found in the Pilbara Craton of Western Australia, and in contrast to accretionary greenstones of the Superior or Kaapvaal cratons, which young across preserved cratonic nuclei.…”