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High Resolution Bio-Chrono-Stratigraphic Framework for Application in Basin Analysis and Sequence Stratigrphy of Jaisalmer Basin, Rajasthan, India

Harswaroop S. Aswal, M. S. Murthy, and M. Shanmukhappa
Regional Geoscience Laboratories, Oil & Natural Gas Corporation Ltd., Vadodara, India

Jaisalmer Basin represents eastern shelf part of large Indus basin, its more than 7km thick sedimentary column is represented by Proterozoic - Quaternary sediments.

Construction of biochronostratigraphic framework,the prime objective of the study, for application in basin analysis and sequence stratigraphy has been achieved through Dinoflagellate cyst based biochronostratigraphic studies and synthesis of available biostratigraphic data to have an absolute understanding of the exploration avenues through a focused approach.

The study provides absolute age dates for various formations encountered in the subsurface, and for seven major and five minor hiatuses along with their span. It also suggest subdivision of Bhuvana Formtion in to lower unit of Permian and upper of Carnian - Norian (Late Triassic) age with a hiatus of 20 Ma, demarcation of Jurassic - Cretaceous boundary with a hiatus of 6Ma, presence of a hiatus at the top of Lower Goru of 6Ma, variable duration of hiatus along K/T boundary from 60 - 14Ma, and the presence of 28Ma hiatus at the top of Late Eocene i.e. Paleogene / Quaternary boundary.

The study reveals deposition of Birmania Formation in over all marine setting under reducing conditions, Bhuvana in fluvio-deltaic to shallow marine environment, Lathi under fluvio-deltaic, and Jaisalmer in high energy to open marine conditions. Baisakhi-Bhadasar is deposited in coastal - shallow marine environment while Pariwar in fluctuating high and low energy conditions. Habur, Goru and Parh are deposited in transgressive regime with increasing bathymetry towards top. The Tertiary sedimentation took place under transgressive regime that ended in Late Eocene with abrupt withdrawal of sea from Jaisalmer Basin.

The biochronostraigraphic studies has helped in identification of three Ist order depositional sequences viz. i) Proterozoic - Early Cambrian rift sequence, ii) Permian - Middle to Late Eocene shelf sequence and iii) Pleistocene - Recent foreland sequence related to Himalayan orogeny. The Permian - Middle to Late Eocene shelf sequence has been further subdivided in to three IInd order sequences viz. i) Permian to Late Jurassic, ii) Early to Late Cretaceous and iii) Paleocene to Middle-Late Eocene IInd order sequences. The application of the present study has resulted in construction of sequence stratigraphic frame work of Jaisalmer Basin and helped in constructing paleogeographic maps for individual sequences and systems tract.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery