Longitudinal trends in the Dockum Group: variations in the Late Triassic megamonsoon

Abstract

Recent work has identified the Late Triassic Dockum Group of West Texas and New Mexico as a fluvial system which records abundant supercritical flow in upper-flow-regime channels fed by megamonsoons. Lithofacies and fluvial architectural elements were recently characterized in this system, yet the scope of the field area for this study was geographically limited. This field study extends the field area to a reach of 425 kilometers to assess how the fluvial system varies longitudinally. Using paleocurrent data and lithosomes—groupings of lithofacies and architectural elements—this study characterizes the trends in flow rates of Dockum Group channels from the headwaters to locations down dip. The cyclic nature of the Late Triassic megamonsoon climate pattern is noted through observations of alternating dying and strengthening of flow strength down dip.