Sedimentary petrography and sedimentary structures of the Cambrian Hickory Sandstone member, Central Texas

Abstract

The basal Cambrian Hickory Sandstone marks the beginnings of Paleozoic sedimentation in Central Texas. It is a bimodal well rounded, poorly sorted, fine and coarse sandstone. About half the samples are orthoquartzites, the remainder being divided between subarkose and quartzose subgraywacke. Well developed cross-beds in the lower Hickory exhibit a very uniform southeasterly direction, and were produced by marine currents controlled by northwest-southeast Pre-Cambrian ridges on a southeast paleoslope. Metamorphic quartz increases to the southeast. Approximately 75% of the feldspar found is orthoclase; the remainder is twinned microcline. The Hickory Sandstone is largely marine, but was derived from desert dune sands which were in turn derived from the Llanoria land mass to the southeast and the Texas Craton to the northwest