for undisturbed deposits useful for establishing a chronological framework for the area, further excavations began in 1971 and continued for nearly 7 years. Naming The archaeological site Gatecliff Rockshelter is named after the Silurian Gatecliff Formation, in which rock shelter occurs. It is made up of chert and dolomite strata. Excavation After the initial discovery in 1970, Thomas and a crew from the University of California Davis began an extensive, large scale excavation. By the end of the first season, the crew had excavated a 7 meter long and 3 meter deep trench. Research continued in 1973 with the sponsorship of the American Museum of Natural History and Expeditions International. The excavations that year reached a depth of 4.8 meters and obtained radiocarbon dates of approximately 2500 B.C. In 1974, the American Museum of Natural History and Education Expeditions International again sponsored the excavations at of Gatecliff Rockshelter again. By the end of this season, the crew had excavated 98 cubic meters of deposits. Due to the danger of the steep and exposed sidewalls, the excavation strategy switched from vertical to horizontal. Starting in 1975, the excavators at Gatecliff removed stratigraphic layers one by one based on their natural levels. Natural levels were determined by the different strata in the deposits seen in the excavation profile. Horizontal strategies continued in 1976 in which the excavators ultimately removed deposits until reaching bedrock. Excavations were completed in late August 1978 with a depth of nearly and a total of of deposits removed. Vertical excavation The initial objective at Gatecliff Rockshelter, Nevada was establishing and dating a stratigraphic sequence that could be applied regionally in the Great Basin area; this would require a vertical excavation strategy. During the early excavations, the deposits were troweled and screened with a 1/8 inch mesh screen. The vertical excavation revealed a pattern of periodic floods that filled the rock shelter with silt and, when dried out, people exploited it again. Due to the hazardous, steep walls produced by the vertical excavation, Thomas and his crew changed their strategy in 1975 as well as their primary objectives; instead of working on exposing a deep, stratified profile, the crew began to remove the deposits over a larger horizontal area to document activity areas. No further excavation occurred on the sidewalls. Horizontal excavation During the excavations, Gatecliff Rockshelter proved to be more useful than just for chronology. The new objective