of the Singhora-Saraipali area, south-eastern Chattisgarh Basin - fieldi

Introduction
The Chattisgarh Basin, a major Purana basin in the Bastar craton, extends from
20º30' N to 22º30' N and 80º45' E to 83º45' E and covers an area of about 36,000 sq
km (Ramakrishnan and Vaidyanadhan, 2008) (fig.1). The c. 2500 m thick succession
of the Chattisgarh Basin comprising conglomerate, sandstone, shale, and carbonates
with tuffs at different stratigraphic levels is designated as Chattisgarh Supergroup,
which is unconformably overlies the Archaean crystalline basement rocks. The
Chattisgarh Supergroup has been classified into Chandarpur and Raipur Groups
(Dutt, 1964; Schnitzer, 1969; 1971; Murti, 1987; Das et al, 1992; Datta, 1998;
Patranabis-Deb, 2004 and Patranabis-Deb & Chaudhuri, 2008). Two unconformity
bounded groups were subsequently introduced, the Singhora Group underneath the
Chandarpur Group (Das et al., 1992; 2003) and Kharsiya Group overlying the Raipur
Group (Patranabis-Deb & Chaudhuri, 2008).
Singhora and Chandarpur Groups consist of immature siliciclastics deposited
in fan delta-prodelta, tide-storm dominated prograding shelf and high-energy coastline
environments (Murti, 1987; Das, et al, 1992 & 2003; Datta, 1998; Patranabis-Deb and
Chaudhuri, 2002 and 2007). Immaturity of the deposits in this lower part of the
succession indicates the unstable tectonic condition. Siliciclastic-carbonate deposits of
the Raipur Group are deposited in muddy shelf and platformal environment, indicative
of more stable tectonic condition and the deposition is controlled by several cycles of
transgressions and regressions (Murti, 1987 and Patranabis-Deb & Chaudhuri, 2008).
From the sedimentary assemblage, facies analysis and stratigraphic architecture it has
been inferred that the Chattisgarh Basin evolved as an intracratonic rift basin
(Chaudhuri et al., 1999; 2002; Roy & Prasad, 2001; Patranabis-Deb & Chaudhuri,
3