Palaeoenvironment and provenance signatures inferred from quartz grain surface features: A case study from Huatabampo and Altata beaches, Gulf of California, Mexico

Abstract

Microtextures on quartz grains from the Huatabampo (HB) and Altata (AA) beaches, Gulf of California, were analyzed by a scanning electron microscopy (SEM) to infer the depositional history and provenance. In total, 41 microtextures were identified and grouped as mechanical, mechanical/chemical, and chemical mode of origins. Among them, twenty-three microtextures represent mechanical, eight represent mechanical/chemical, and ten represent chemical origin. The microtextures of chemical origin were further classified as dissolutional and precipitational origins. Oriented etch pits, solution pits, solution crevasses, and scaling are classified as of dissolutional origin. Silica globules, silica flower, silica pellicles, crystalline overgrowth, trapped diatoms, and halite crystals are grouped as chemical precipitational origin. The V-shaped marks, straight and curved scratches revealed the combination of fluvial and high energy subaqueous beach environments. The low frequencies of upturned plates, abrasion fatigue, meandering ridges, crescentic percussion marks, bulbous edges and elongated depressions suggest the low abundance of sediments derived by aeolian transport. The microtextures of chemical origin in few grains indicated the diagenetic processes in a silica saturated intertidal zone. The quartz grains from HB and AA beaches reveal varying sizes of conchoidal fractures indicate that they were derived mainly from crystalline source rocks. The association of straight and arcuate steps along with conchoidal fractures further support that the studied quartz grains were liberated from crystalline rocks. The dominance of angular to sub-angular grains indicates short transport and rapid deposition. In addition, straight and arcuate steps are delicate features which might have been destroyed during long transportation. Thus, the presence of straight and arcuate steps features together with angular to sub-angular grains support a nearby source.