Seismic imaging of Paleogene sediments of Kachchh Shelf (western Indian margin) and their correlation with sea-level fluctuations

Abstract

The sedimentary history of Kachchh offshore (central western Indian margin), especially since the eruption of the Deccan Traps (∼65 Ma), has remained scantily studied despite an area with promising resource potential. Of late, new marine surveys combined with industrial drilling along the Kachchh shelf are beginning to elucidate the depositional history of this region. Here, we attempt to synthesize interpretation of new offshore seismic data, along with borehole information and long-term sea-level variations to provide a coherent sedimentological and lithostratigraphic framework over the past ∼65 Ma in this area. Based on integrated interpretation of information derived from complementary sources, Paleogene successions of Kachchh shelf are investigated. Six major seismic facies are identified and attributed to post-Cretaceous sea-level fluctuations. Each lithological unit mapped on the seismic sections suggests coeval sedimentation in the area. Variable geometry and seismic characters of the identified facies are noted and attributed to the evolutionary history of this region. Recognized seismic horizons are distributed uniformly and are inferred to have regional significance. Apparently, the sea-level fluctuations in the past have played a major role over geodynamic contributions in terms of sediment deposition in this region. The incessant sea-level changes have resulted in transgression–regression type sediments throughout the area. Regular but low levels of tectonism are inferred from the seismic sections in the form of faults. Each sediment unit reflects dual signatures of eustatic sea-level changes as well as structural activities. Integration of lithologs with seismic data also suggests that the area was dominated by carbonate sedimentation during the Paleogene. The most important aspect of this study is to provide sub-surface images that illustrate stratigraphic details of the Paleogene sediments with significant resource potential.