Pilot study on provenance and depositional controls on clay mineral coatings in active fluvio-eolian systems, western USA

Abstract

Understanding the distribution of grain coating minerals in sandstones may be crucial in evaluating the reservoir quality of deeply buried lithologies since they can inhibit syntaxial overgrowth cementation and thus preserve intergranular pore space. In unconsolidated sediments, the presence of clay mineral grain coatings and their coverage are often related to the depositional subenvironment, grain size, sorting, and skewness. These properties are interpreted to reflect the amount of clay minerals present to form coatings and relate to sediment transport and reworking. Samples from three active fluvio-eolian depositional systems in the USA (Mesquite Flat Sand Dunes, near Stovepipe Wells, CA; Algodones Dunes, near Brawley, CA; and Coral Pink Sand Dunes, near Kanab, UT) were studied using petrography (transmitted light and SEM) and XRD analyses to test and apply the available correlations to fluvio-eolian sediment samples. The frequently used correlations to the depositional subenvironment, grain size, sorting, and skewness only show poor fits (R2 < 0.25). Highest grain coating coverages are present in fluvial channels near Algodones Dunes (81%). Remobilization and abrasion lead to slightly reduced average grain coating coverages (47%) in eolian deposits located in the transition zone to the main dune field. Deposits within the main dune field show smaller average grain coating coverages (29%). Sediments supplied from a limestone rich provenance in Mesquite Flat Sand Dunes contain grain coating coverages in a range from 20 to 42%. In Coral Pink Sand Dunes sediments sourced from mature Jurassic Navajo sandstones contain the smallest average grain coating coverages (15%) indicating that source rock maturity and composition can control the coating coverage. The sediment source area and the proximity to areas where clay mineral coated grains are formed are interpreted to be the main controls on inherited grain coating coverages in the studied recent fluvio-eolian deposits.