with a horizontal excavation at the rock shelter, the previous being chronology, emphasized the reconstruction pre-historic activities and events that occurred at the site. The focus shifted to finding artifacts and mapping them on large-scale living floor maps. In 1975, over a period of ten days, the crew removed a massive chert roof fall that covered half of the rear of the rock shelter. The excavation units were removed by the visible natural levels or strata; if natural levels exceeded , arbitrary levels were created within the natural levels. Bags of deposits were passed outside of the cave and then screened outside. Stratigraphy The decade of excavations from 1970 to 1978 exposed a remarkable stratigraphic sequence at Gatecliff Rockshelter. The lack of erosion and episodic deposits of sediments due to water provided a well-defined and intact cultural sequence that could be applied to the Great Basin area. The deposits consisted of 56 geological strata with 16 cultural horizons; 23 strata contained rubble and 33 contained fine silt material. The deposits also include a layer of tephra from Mount Mazama's eruption about 6600 to 7000 B.P. The stratigraphy can also be divided into eight stages to reflect a specific climatic regime. Forty-seven radiocarbon dates were obtained and thoroughly ground the chronological sequence of Gatecliff Rockshelter. Paleontology In Gatecliff Rockshelter, the excavators recovered over 51,000 animal bones. Donald K. Grayson identified and analyzed approximately 13,000 bones and teeth of small mammals. Due to the nature of the rock shelter and the lack of taphonomic knowledge, Grayson argued that the processes that produced this massive collection of bones could not be determined. It could be a result of human activities, other animals, and natural processes. These small mammals include rabbits, chipmunks, squirrels, gophers, rats, voles, mice, dogs, and coyotes; only two of the taxa found at Gatecliff are absent from the present Toquima-Monitor area. Large mammal remains represent the bulk of the bones found at Gatecliff. Roughly 90% of the bones came from the bighorn sheep, a major prey of high-altitude hunters. Other large mammals include pronghorn, elk, and bison. On a smaller scale, approximately 500 elements of amphibians and reptiles were recovered. The amphibians and reptiles at the rock shelter include lizards, toads, and snakes. Material culture The excavations at Gatecliff Rockshelter recovered over 400 projectile points. From this large collection of identifiable projectile points, Thomas was able to identify specific projectile