The Nullarbor Plain of southeastern Australia, ∼200,000 km 2 in area, is flat and mostly treeless. It contains widely scattered collapse dolines and a few hundred caves, some of which are large and extensive. Initial karst development probably occurred during the warm, seasonally wet climatic conditions of the Oligocene, when the withdrawal of the sea exposed the recently deposited Eocene Wilson Bluff Limestone for over ∼10 m.y. Several major conduits probably developed at this time. These were flooded by the return of the sea, which finally retreated in the late Miocene followed by regional uplift. Cave formation in the Pliocene and Quaternary was inhibited by the semiarid climate, which became increasingly arid ca. 1 Ma. The overall dryness caused crystallization of evaporite minerals in cracks and pore spaces within the limestone walls of the caves, and they suffered extensive collapse, producing large passages, dome chambers, and dolines. However, during a wet phase 5–3 Ma, rivers extended across the karst plain, and caves formed where they sank into the limestone. Shallower caves probably also formed at this time, perhaps associated with perched water tables. The Nullarbor Plain did not develop extensive surface and underground karst features, even during the wetter climate of the Oligocene. It appears that the flatness of the plain and the particular characteristics of the limestone (primary porosity and lack of jointing and inception horizons) resulted in relatively uniform downwasting and little cave formation. Climate played a relatively minor role in restricting karst development.

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 Burnsville Cove in Bath and Highland Counties (Virginia, USA) is a karst region in the Valley and Ridge Province of the Appalachian Mountains. The region contains many caves in Silurian to Devonian limestone, and is well suited for examining geologic controls on cave location and cave passage morphology. In Burnsville Cove, many caves are located preferentially near the axes of synclines and anticlines. For example, Butler Cave is an elongate cave where the trunk channel follows the axis of Sinking Creek syncline and most of the side passages follow joints at right angles to the syncline axis. In contrast, the Water Sinks Subway Cave, Owl Cave, and Helictite Cave have abundant maze patterns, and are located near the axis of Chestnut Ridge anticline. The maze patterns may be related to fact that the anticline axis is the site of the greatest amount of flexure, leading to more joints and (or) greater enlargement of joints. Many of the larger caves of Burnsville Cove (e.g., Breathing Cave, Butler Cave-Sinking Creek Cave System, lower parts of the Water Sinks Cave System) are developed in the Silurian Tonoloway Limestone, the stratigraphic unit with the greatest surface exposure in the area. Other caves are developed in the Silurian to Devonian Keyser Limestone of the Helderberg Group (e.g., Owl Cave, upper parts of the Water Sinks Cave System) and in the Devonian Shriver Chert and (or) Licking Creek Limestone of the Helderberg Group (e.g., Helictite Cave). Within the Tonoloway Limestone, the larger caves are developed in the lower member of the Tonoloway Limestone immediately below a bed of silica-cemented sandstone. In contrast, the larger caves in the Keyser Limestone are located preferentially in limestone beds containing stromatoporoid reefs, and some of the larger caves in the Licking Creek Limestone are located in beds of cherty limestone below the Devonian Oris-kany Sandstone. Geologic controls on cave passage morphology include joints, bedding planes, and folds. The influence of joints results in tall and narrow cave passages, whereas the influence of bedding planes results in cave passages with flat ceilings and (or) floors. The influence of folds is less common, but a few cave passages follow fold axes and have distinctive arched ceilings.