Connection between climate and tectonics: implication to Kolhan basin evolution in the Proterozoic

Abstract

A simple logical model for the development and evolution of the Kolhan Basin is proposed. The first event consists of a rapid stretching of the continental lithosphere, which produced thinning and passive upwelling of hot asthenosphere. This stage is connected with block faulting and subsidence. This is synchronous to the existence of the Columbia supercontinent. There was no glaciation during the existence of Columbia. This indicates moderate weathering rate during which the Kolhan Basin formed. This simplistic logical conclusion is supported by the predominance of quartz arenite in the sandstone of the basin . The paucity of feldspars in the thin sections supports the above findings. The main shallow elongated basin of the Kolhan Formation extends from Chaibasa (85° 48’, 22° 33’) to Noamundi (85°28’, 22° 09’) covering about 34 miles in length and maximum 10 miles in width along the western extremity of the Singhbhum Granite. The occurrence of detached outliers of the Kolhan rocks east of the unconformity on Singhbhum Granite and north of Chiabasa  suggests the wide extent of the Kolhan basin in the past. The petrography and geochemistry of the basin concludes an intracratonic rift tectonic setting in Proterozoic time. This indicate a granitoid source with moderate chemical weathering. High Al2O3/SiO2 and K2O/Na2O ratios reflect a derivation of all the sediments from stable cratons during tectonic quiescences. These alumina ratio indicates that the clastics were deposited in a passive margin or cratonic margin. The existence of Columbia supercontinent during the life of Kolhan Basin indicates no glaciation during that time. This scenario is well supported by findings of petrography and geochemistry of the basin.