Quartz grain microtextures in the Boca del Cielo and Chocohuital beaches in the Mexican Pacific, Chiapas state: implication on paleoenvironment

Based on scanning electron microscopy (SEM) images, we studied the microtextures of quartz grains recovered from the Boca del Cielo and Chocohuital beach sediments in the Chiapas state, Mexico. Microtextures of mechanical, chemical, and mechanical/chemical origins were identified. Quartz grains in both beaches were sub-angular to sub-rounded in shape, indicating high energy, short transport, and nearby source. The microtextures of mechanical origin like percussion marks, conchoidal fractures, and V-shaped marks were abundant in the Chocohuital beach, which revealed high energy subaqueous beach environment. Large-scale conchoidal fractures are characteristic of crystalline rocks, and abrasion features are due to energetic grain-to-grain collision during eolian transport. However, quartz grains in the Boca del Cielo beach were dominated with microtextures of chemical origin such as adhered particles, solution pits, and crystal overgrowth, and are abundant with trapped diatoms, which indicated the diagenetic processes in a silica saturated environment. Two diatoms Navicula incertata and Cyclotella bodanica of 15-μm size are identified in Boca del Cielo quartz grains.