Microtextures on quartz grains in the Kuakata beach, Bangladesh: implications for provenance and depositional environment

Microtextures on fine to medium-grained quartz grains (65-500 mu m) from three sections, i.e., Laboni, Kuakata, and Jhauban points of the Kuakata beach area, Bangladesh, were examined by a scanning electron microscope (SEM) to determine the transport history, provenance, depositional environment, and paleoclimate. Thirty microtextures were observed on 180 quartz grains, which were subsequently classified as mechanical (20 features), chemical (5 features), and combined mechanical and chemical (5 features) origins. The abundance of sub-rounded to rounded quartz grains with smooth outlines, V-shaped pits, straight or curved grooves, crescent-shaped features and straight or arcuate steps, indicates that the quartz grains experienced long-distance transport through fluvial environment (e.g., Himalayan sediments). The angular to sub-angular quartz grains with straight or curved grooves, straight steps, and adhering particles inferred that they were probably derived from adjacent landmasses (e.g., Chittagong-Tripura Folded Belt and/or Indo-Burman Ranges). The well-rounded outlines, low relief with dish-shaped depressions, mechanically upturned plates, and arcuate steps were also observed, indicating aeolian processes in shoreface or beach environment. Etching, solution/irregular pits, and differential relief observed in the quartz grains indicate a subaqueous collision in fluvial and nearshore environments.