Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India

Chapter 5 Controls on sedimentation in Indian Palaeoproterozoic basins: clues from the Gwalior and Bijawar basins, central India

“…Table 5.1 summarizes the facies types and facies associations present within the Par succession. Using processbased sedimentology and channel bedform cross-bed thicknessbased palaeohydraulic estimation, Chakraborty & Paul (2014) modelled the basal part of the Par sandstone as a product of an alluvial fan and braid plain system. An overall dominance of sheetflood and braid streamlet products within the fan system ( Fig.…”

“…An overall dominance of sheetflood and braid streamlet products within the fan system ( Fig. 5.4a, b) prompted these workers to infer the Par alluvial fan as a dry-climate fan, dominantly represented by its midfan zone below the intersection point (Chakraborty & Paul 2014). Independent support for a dry-climate condition was sought from estimation of stream discharge data and the chemical index of alteration values (Absar et al 2009) obtained from sandstones.…”

“…signature for dry climatic conditions; in the case of Gwalior Basin it is inferred from a low stream discharge value (Chakraborty & Paul 2014), whereas the thick Malhera Chert Breccia Formation and illite and sepiolite in the Gangau Subgroup within the Bijawar Basin bear testimony to such inference (cf. Pufahl 2010).…”

“…In this context, Palaeoproterozoic (2500 -1600 Ma) and late Palaeoproterozoic (2000( -1600 in particular, refers to a time window when many secular changes, including the Supercontinent cycles, happened in most dramatic way (Nance et al 1986;Reddy & Evans 2009;Eriksson et al 2013), often in a manner that was progressive, unidirectional or at times, periodic and bumpy. On land, lack of vegetation engendered more slope failures, landslides and debris flows unlike their present analogues, and promoted more scree cones, alluvial fans and braided rivers (Els 1998;Bose et al 2008;Chakraborty & Paul 2014), whereas in oceans organic carbon burial leading to large-scale sea-water carbon-isotopic excursion at 2.1 Ga (the Logamundi event) and deposition of large-scale continental margin iron formation represent two major non-uniformitarian events. Also, globally high sea-levels associated with the Palaeoproterozoic 'Supercontinent' cycles resulted in flooding and chemical sedimentation on continental margins, including extensive development of carbonate platforms (Bartley & Kah 2004;Bekker et al 2005) and deposition of phosphorite, chert and evaporite, some of which stand out as the earliest record of their category in the Earth history.…”

“…Only in recent times, the clastic Par Formation at the basal part of the Gwalior succession has been studied geochemically (Absar et al 2009) and with employment of process-based sedimentology (Chakraborty & Paul 2014). There is no available knowledge on the Morar Formation except that it is dominated by rocks of BIF, either in association with chert or shale.…”