Provenance, Tectonic Setting and Paleoclimate of the Bhuban Formation Exposed in Jampui Hills, Tripura Fold Belt, Tripura, India: Insights from Petrography and Clay Mineralogy

Abstract

The sandstones of the Bhuban Formation (Miocene) exposed in the Jampui hills of Tripura Fold Belt, India has been studied for provenance, tectonic setting and paleoclimate using the petrography, heavy mineral assemblage and clay mineral studies. The detrital mode of the sandstones indicate that the sediments consists predominantly of detrital quartz (avg. 92.19%), with subordinate proportions of feldspar (avg. 4.55%) and rock fragments (avg. 3.25%). The provenance discrimination diagrams depict the derivation of the detritus from both plutonic and metamorphic source rocks having affinity to continental block provenance. The plots of QFR and semi quantitative weathering index of the clastics support a moderate degree of paleoweathering in the source area under humid climatic condition. The presence of zircon, tourmaline, rutile, kyanite, epidote, sillimanite and garnet in the Bhuban sandstones is ascribed to the provenance of plutonic and metamorphic rocks. Dominance of zircon in the heavy mineral assemblage and the ZTR index values (75.13% avg.) indicate towards moderate degree of maturity with long distance of transport. The study of the shale samples by XRD and SEM analyses shows the dominance of illite over kaolinite and montmorillonite. The presence of minor amount of montmorillonite may suggest the addition of tuff and volcanic ash in the sediments under alkaline environment.