Microtextures on quartz grains from the Gulf of Mexico and the Mexican Pacific coastal sediments: Implications for sedimentary processes and depositional environment

摘要

Microtexture analyes on quartz from coastal sediments of the Gulf of Mexico and the Mexican Pacific Coast reveal 35 and 30 types of microtextures, respectively which grouped into mechanical, mechanical/chemical and chemical categories based on their mode of origin. Microtextures of chemical origin are rarer in the El Carrizal than in the Manzanillo beach sediments of the Mexican Pacific Coast. Microtextures of mechanical origin like straight and curved scratches, pits, broken edges, and V-shaped marks indicate high energy, fluvial to marine depositional environments. The scarcity to absence of chemical features suggest that the energy level was higher at the Mexican Pacific coast than on the Gulf of Mexico coast. V-shaped marks are common in the Gulf of Mexico sediments, whereas they are abundant in the quartz grains from the Mexican Pacific coast. Increased frequency and density of V-shaped marks are produced by exceedingly high wave velocity during storm events or tsunamis. Abundance of V-shaped marks with fresh surfaces of quartz grains from the Mexican Pacific coast indicate an extremely high-energy impact event. Many quartz grains from the El Carrizal beach of the Mexican Pacific coast have abundant closely spaced V-shaped marks with fewer fresh surfaces. Such high frequency of V-shaped marks is mainly linked to grain-to-grain collision, typically associated with high-energy sub-aqueous conditions with a large volume of sedimentary particles in the water column that are produced during a tsunami or storm events. In contrast, many quartz grains from the Gulf of Mexico have large fresh surfaces with moderate percentages of V-shaped marks that might have been produced by high-energy waves with low sediment concentrations during storm events.