Ordovician graptolites of the Basin Ranges in California, Nevada, Utah, and Idaho

In the Basin Ranges, Ordovician graptolites have been found in two contrasting lithic facies; the "western" or eugeosynclinal facies is composed of greenstone, shale, siliceous argillite, chert, and quartzite, whereas the "eastern" or miogeosynclinal facies is composed of limestone, dolomite, silty limestone, calcareous shale, and quartzite. Graptolites are the most common fossils in the eugeosynclinal strata and probably far more abundant in the miogeosynclinal facies than is generally supposed.