Stromatolites of the Lower Cambrian Deep Spring Formation; Mount Dunfee, Esmeralda County, Nevada

The Middle Member of the Lower Cambrian Deep Spring Formation at Mount Dunfee, Nevada contains a diverse assemblage of stromatolites that formed on a tideand storm-dominated, siliciclastic-influenced, carbonate shelf. The stromatolites formed in a shallow subtidal environment within and near active oolite shoals under strongly focused currents. The stromatolites occur in four different lithofacies: (1) bioherms of digitate stromatolites, (2) bioherms and biostromes of inclined stromatolites, (3) isolated forms of massive and hemispheroidal stromatolites, and (4) a biostrome of cryptomicrobial boundstones. The first three lithofacies are interpreted as microbial reefs. They had topographic relief, formed in active agitated waters, and exerted a physical control over their environment. The stromatolites incorporate an average of 16% very-fine grained detrital quartz within their microstructures. These quartz-bearing stromatolites are