Compositional evolution of siliciclastic sediments recording the tectonic stability of a pericratonic rift: Mesozoic Kutch Basin, western India

This study presents a combined petrographical and geochemical investigation to track the compositional changes in the Mesozoic sedimentary record during the evolution of the pericratonic rift basin of Kutch. The Mesozoic sequence of the proven petroliferous basin of Kutch, representing similar to 3000 m thick siliciclastic and carbonate deposition within a time frame of similar to 70 Ma, consists of Jhurio, Jhumara, Jhuran and Bhuj formations in ascending order of succession. The dominance of arkosic sandstones and the abundance of zircon and monazite indicate predominantly felsic source rocks. The concentration of individual trace elements such as Th, Sc, Zr, V, Ni and ratios like Th/Sc, Cr/V, Y/Ni, Th/Co, La/Sc support the predominantly felsic source rock. The LREE enrichment and the negative Eu anomaly corroborate the predominantly felsic source. However, concentrations of V, Ni and Ti reveal the mafic input in older stratigraphic units. While (Gd-N/Yb-N) indicates dominant post-Archean source across the Mesozoic succession, younger stratigraphic units reveal contributions from the Archean rocks, from Nagar Parkar and Aravalli highland regions. The CIA values suggest intermediate to intense weathering, while the ICV data record a shift from immature sediments in the older formations to mature and recycled types in the younger formations. The high value of Zr/Sc as well a high content of Hf reflects the addition of zircon by recycling or by erosional unroofing of older continental rocks. Major oxide (SiO2, Na2O and K2O) and trace elements (La, Th and Hf) bear the passive margin setting for the Kutch Basin during the Mesozoic. The decrease in feldspar content (in sandstones), increase in the concentration of Zr and Hf (in shale) and a decrease in values of ICV from older to younger stratigraphic units corresponds to the compositional evolution related to increased stability of the Kutch basin during the transition from early syn-rift to post-rift.