Dataset for Sediment Mixing in a Proglacial Catchment at Prestahnukur Volcano, Iceland: Implications for Silicic Deposits at Gale Crater, Mars

Abstract

The discovery of silica polymorphs in the Buckskin mudstone at Gale Crater has important implications for understanding high-temperature processes on Mars. Three deposition/formation mechanisms have been proposed: direct deposition of silicic volcanic ash, in-situ hydrothermal alteration of sedimentary bedrock, or fluvial transport and concentration of eroded silicic material from within the Gale Crater catchment in an ancient lake. To evaluate the transport hypotheses, we conducted a source-to-sink study at Prestahnúkur Volcano, Iceland, where silicic materials exist within a predominantly basaltic terrain. Through systematic sampling at 0.2 km intervals along two distinct sediment transport pathways, we characterized the spatial evolution of physical and compositional sediment properties using particle size analysis, X-ray diffraction, and X-ray fluorescence. Our results reveal three key findings: (1) physical sorting of sediments occurs upstream from effective mineralogical and chemical mixing, (2) mixing between silicic and mafic components is extremely efficient once initiated, achieving near-complete homogenization over distances less than 0.4 km, and (3) palagonitic materials significantly influence sediment chemistry during transport, producing characteristic enrichments in FeO, Ni, and Cr. The observed rapid homogenization of sediment compositions  reduces the likelihood of catchment-derived transport as a viable mechanism for concentrating silicic materials in the Buckskin mudstone, as any silicic material from Gale Crater's walls or central peak would have been thoroughly mixed with basaltic components before reaching the depositional site. These findings narrow the possible formation mechanisms to either direct volcanic ash deposition or in-situ hydrothermal alteration, providing important constraints for understanding the geological history of Gale Crater.