Petrography and geochemistry of the Dupi Tila formation: Implications for depositional environment and tectonics

Abstract

A comprehensive examination of detrital sandstone modes from the Sylhet Trough reveals a diverse range of sub-lithic to sub-feldspathic quartz arenites. Soil samples were gathered from Dupi Gaon (Jaintiapur) in Bangladesh, followed by a thorough analysis using field examination, X-ray diffraction (XRD), X-ray fluorescence (XRF), petrography, and heavy mineral concentration analyses. Field observations revealed the soil sample varying from white to yellowish to variegated, with thicknesses ranging from 15 cm to about 4 m, and exhibiting moderate softness. XRF analysis revealed significant SiO₂, Al₂O₃, and Fe₂O₃ levels in the samples, with zirconium (Zr) and copper (Cu) showing consistently high concentrations. XRD analysis identified quartz as predominant, along with muscovite, biotite, and accessory minerals like rutile and magnetite. Petrographic analysis highlighted quartz as dominant, with fractures suggesting tectonic influences, while heavy mineral separation techniques identified zircon, garnet, goethite, rutile, and magnetite. These findings provide insights into sediment provenance, depositional processes, and environmental conditions during the formation of the Dupi Tila Formation. The comprehensive geochemical data of the entire rock indicates that most of the sediments originated from felsic igneous sources, and also suggests a moderate to high level of weathering in the source region. Overall, the analyses suggested an in situ origin of the Dupi Tila Formation, with parent materials being predominantly detrital rather than authigenic, supported by the presence of detrital quartz and an assessment of the depositional environment, providing insights into the geological conditions of the era and potential modes of sediment transportation.