Storm-dominated Lower Cambrian depositional environments in the Ravenswood area, Lander County, Nevada

Abstract

A Lower Cambrian sedimentary sequence more than 200-m-thick is exposed in the Ravenswood area, Lander Country, Nevada. 40 meters of this sequence was divided into 7 lithofacies interpreted to represent littoral to sublittoral marine environments which include offshore bars, sheet deposits (proximal, intermediate, distal), patch reefs, and storm-surge-ebb channels. The lithology, paleontology, and sedimentary structures reflect deposition in a storm-dominated system. Paleocurrent indicators suggest that strong westerly (present orientation of continent) winds created landward-directed currents transporting carbonate debris from the shelf to nearshore environments. Subsequently, storm-surge-ebb flows transported nearshore sediments seaward. The lithofacies indicate that sediments were composed of mixtures of carbonate and siliciclastic material during deposition. The processes responsible for this mixing are punctuated mixing (occurred as a result of storm-transported carbonate sediment into a siliciclastic environment), and facies mixing (occurred with the forming of archaeocyathan bioherms). These bioherms are interpreted to have formed as isolated patch reefs in the sublittoral zone.