Palaeoenvironmental reconstruction based on palynofacies analysis of the Early to Middle Jurassic of the Lathi Formation, Jaisalmer Basin, India

摘要

Twenty-four sedimentary samples collected from a succession of the Lathi Formation exposed near the Tamira Rai Temple, Jaisalmer Basin, western India, are subjected to palynofacies analysis for the palaeoenvironmental interpretations. Based on the quantitative composition of the various types of sedimentary organic matter, two distinct palynofacies associations (PF-I and PF-II) have been recognized, which are respectively reflecting over depositional settings in a proximal-distal suboxic-anoxic shelf and proximal oxic basin. The sediments are found rich in amorphous organic matter (AOM) through palynofacies analysis under the present investigation. PF-I is characterized by the dominance of AOM and sub-dominance of the opaque phytoclasts, and PF-II is dominated by the occurrence of the opaque phytoclasts. Dominant occurrence of the phytoplankton derived organic matter in the PF-I suggests its deposition in the marginal/shallow marine settings while the abundance of the opaque phytoclasts and rare presence of the phytoplankton-derived organic matter in PF-II suggests its deposition mainly in the continental settings. The present study suggests a marginal marine setting for the early phase of Lathi Formation contrary to the previous studies.