Published by the American Geophysical Union as part of the Field Trip Guidebooks Series, Volume 125. Field Trip T125 of the 28th International Geological Congress will give participants a regional overview of the geology of the Basin and Range province and an introduction to Cambrian and Early Ordovician stratigraphy and paleontology. Emphasis will be placed on regional stratigraphy, depositional environments, biofacies and lithofacies relations, biostratigraphy, trilobite mass extinctions ("biomere boundaries"), evidence for eustatic sea-level changes, paleotectonic history, and paleogeographic reconstructions. A transect will be made across a Late Cambrian and Early Ordovician passive continental margin from deep-water-carbonate submarine-fan and slope facies in central Nevada to temporally equivalent shallow-water microbial bioherms, and carbonate sand and mud facies in eastern Nevada.