Petrofacies, provenance, and paleocurrent analysis of Pachmarhi sandstone (Early Triassic), Satpura basin, Central India
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ORIGINAL PAPER
Petrofacies, provenance, and paleocurrent analysis of Pachmarhi sandstone (Early Triassic), Satpura basin, Central India Abdullah Khan & Anis & Sarwar Rais
Received: 23 January 2012 / Accepted: 26 June 2013 # Saudi Society for Geosciences 2013
Abstract The Satpura Gondwana basin hosts a ∼5 km thick siliciclastic succession that unconformably overlies the Precambrian basement. The Gondwana sequence in this basin starts from Early Permian (Talchir Formation) to Lower Cretaceous (Jabalpur Formation). The aim of this study is to (1) identify the source rock (provenance) for Early Triassic Pachmarhi sediments in the Satpura Gondwana succession and (2) to understand the relative role of tectonics and climate in determining the sandstone composition. These sandstones are medium to coarse-grained, moderately to moderately well sorted, subangular to subrounded, of moderate sphericity, and composed of several varieties of quartz, feldspar, rock fragments, and micas. Petrographically, the Pachmarhi sandstones are mostly quartzarenite and subarkose. The petrofacies in Qt– F–L and Qm–F–Lt triangular diagrams show that the bulk of the Pachmarhi was derived from continental (cratonic) source, especially from craton interior. Petrofacies, together with paleocurrent data, suggest that Pachmarhi Formation was deposited by a network of braided river system, which flowed dominantly from southeast to northwest. The study suggests that the sediments were mostly derived from Precambrian granites, gneiss, and metasedimentary basement rocks straddling the southern margin of the basin. Paleocurrent data also corroborates this contention. Keywords Sedimentology . Paleocurrent . Pachmarhi sandstone . Satpura Gondwana basin . Central India
A. Khan (*) : Anis : S. Rais Department of Geology, Aligarh Muslim University, Aligarh, India e-mail: [email protected] Anis e-mail: [email protected]
Introduction The post-Permian Gondwana succession of Satpura basin, Central India is characterized by an alternation of sandstones, conglomerate, and shales. Compared to post-Permian (Upper Gondwana) sequence, the Late Paleozoic (Lower Gondwana) sequence including the coal measures has been studied in great detail in terms of sedimentological studies (Casshyap and Kumar 1987; Casshyap and Srivastava 1988; Casshyap and Tewari 1984, 1988; Casshyap et al. 1993; Tewari 1995; Tewari and Casshyap 1996). Traditionally, Mesozoic Gondwana succession crop out in east central part of Satpura basin comprises the Pachmarhi, Denwa, and Bagra Formations considered to represent a long-term record of alluvial deposition in Satpura basin (Casshyap and Tewari 1988; Casshyap et al. 1993; Khan 1997). However, this Mesozoic Gondwana sedimentation in terms of petrofacies has not yet been properly evaluated. This paper presents a detailed account of Pachmarhi Formation exposed in east–central part of Satpura basin. The Triassic succession in the east–central part of the Satpura basin comprises the Pachmarhi and the overlying Denwa Formations. The Early
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