Abstract On this field trip, you will visit two important archaeological cave sites that provide the most compelling evidence for latest Pleistocene and earliest Holocene human occupation in the Bonneville Basin. Danger Cave, located near Wendover, Utah/Nevada, is famed for its deeply stratified archaeological deposits dating as old as 10,300 radiocarbon yr B.P., when the remnant of Lake Bonneville stood at the Gilbert shoreline. Bonneville Estates Rockshelter, located south of Danger Cave at the Lake Bonneville highstand shoreline, also contains well-preserved stratified deposits, including artifacts and cultural features dated to at least 11,000 radiocarbon yr B.P., making it one of the oldest known archaeological occupations in the Great Basin. We describe results of our recent research at these sites and show the stratigraphic evidence for these earliest human occupations. We also review recent work at the Old River Bed Delta, on Dugway Proving Ground, that has documented hundreds of Paleoarchaic occupation sites dating 11,000–8500 radiocarbon yr B.P. Together these localities give us an unparalleled picture of human occupation during the first few thousand years of known human occupation in the region, during a time of dramatic environmental change. Packrat middens, pollen sampling localities, and geomorphic features that illustrate the history of Pleistocene Lake Bonneville and the environmental history of the western Bonneville Basin will also be observed on this trip .

Abstract Donald R. Currey spent over two decades researching and exploring relics of ancient Lake Bonneville in the eastern Great Basin. Shoreline and deepwater deposits of Lake Bonneville document coastal processes, lake chemistry, and environmental change during the late Pleistocene and Holocene. This field guide summarizes findings at many of the classic localities researched by Currey and colleagues that contributed to the current understanding of this impressive pluvial lake and its interglacial successor, Great Salt Lake. Subjects include coastal processes at Antelope Island and the Stockton Bar; lake history, chemistry and environmental change at Stansbury Island, the Public Shooting Grounds and Hansel Valley; deltaic depositional processes at Big Cottonwood Canyon, American Fork Canyon and Brigham City; and the relative chronology of glacial and lacustrine deposition at Little Cottonwood Canyon and Bells Canyon.

Abstract The central Colorado landscape bears a strong imprint of post-Laramide (late Eocene to Quaternary) tectonics, volcanism, climate change, and drainage rearrangement. This field trip will examine the post-Laramide evolution of central Colorado, traversing the Front Range, from the Colorado Piedmont on the east to the upper Arkansas valley segment of the Rio Grande Rift on the west (Fig. 1 ). The first day of the trip will involve a transect from the Denver-Colorado Springs section of the Piedmont across the southern Front Range, South Park, and Mosquito Range to the upper Arkansas valley. On this day we will focus on questions concerning the roles of tectonics and climate in driving post-Laramide landscape changes, examining structural, sedimentological, paleontological, geomorphic, and fission track evidence that has been used to reconstruct post-Laramide history. We will end the day with an initial overview of rift-related structures, sediments, and geomorphology as we enter the upper Arkansas valley. We will spend the second day in the southern portion of the upper Arkansas valley and the adjacent Poncha Pass transfer zone, examining structural and sedimentological evidence for the nature and timing of Neogene and Quaternary faulting and graben formation, and the character of the transfer zone. On our final day we will traverse back to the Piedmont, this time traveling down the canyons of the Arkansas River. We will examine rift-related structures and sediments in the Pleasant Valley graben and at the northern end of the Wet Mountain Valley, and will discuss the history of Cenozoic and earlier faulting in the area, the evolution of the Arkansas River drainage, and its recent downcutting history. We will end the trip with a discussion of the Neogene and Quaternary erosional history of the High Plains and Piedmont, and possible implications of this history for the driving mechanisms of landscape change.

Little is known for certain about early Wisconsin (isotope stage 4) lakes and glaciers of the Great Basin. A moderate lake-level rise in the Bonneville basin is not well dated, but on the basis of amino-acid and radiocarbon ages, is thought to be early Wisconsin in age. A moderate rise of lakes in the basins of Lake Lahontan is dated as ca. 50 ka by U-series ages on tufa, but may have occurred earlier. In the southern Great Basin, Searles Lake fluctuated at levels below the threshold connecting it with Panamint Valley, and Panamint Valley apparently did not contain a large lake during the early Wisconsin. The glacial record is even less-well dated than the lacustrine record. The extent of glaciers in and around the Great Basin during the early Wisconsin is not known; ice extent was certainly greater than at present, but probably was less than the late Wisconsin maximum in most glaciated valleys. Further work is necessary to refine lacustrine and glacial chronologies, and to investigate the causes of lake vs. glacier expansion. Important clues to these questions will come from detailed studies of lacustrine and glacial sequences in different parts of the Great Basin.