OUTER SHELF TO SLOPE DEPOSITS OF THE LOWER CAMBRIAN POLETA FORMATION, WESTERN GREAT BASIN, NEVADA
The tripartite subdivision of the Poleta Formation, consisting of upper and lower limestone members separated by a siliciclastic member, is also present in the slope sections. The carbonate members at Miller Mountain are metamorphosed to a uniform-appearing, crystalline marble. The lower carbonate member is comparable in thickness to its shelfal counterparts, but the upper carbonate member is several times thicker in the slope environment. The middle clastic member in the shelfal environment consists of a coarsening-up sequence of shales and thin interbedded bioclastic limestones, grading upward into quartz sandstones, while the slope environment is dominated by argillitic and siliceous turbiditic deposits and chert horizons, overlain by polymictic megabreccias and fine-grained quartzitic layers. The distinct faunal change from nevadiid to olenellid trilobites (base of Dyeran Stage) occurs within the middle member of the Poleta at Miller Mountain as it does in the shelf areas to the east.