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Douglass, Richard Ciolek-Torrello, Sarah Van Galder, Benjamin R. The Coleville and Bodie Hills NRCS Soil Inventory, Walker and Bridgeport, California: A Reevaluation of the Bodie Hills Obsidian Source (CA-MNO-4527) and Its Spatial and Chronological Use. Spatial and Temporal Distributions of Archaeological Heated-Rock Cooking Structures in the Transverse Mountain Ranges: Proposed Markers of Land-Use Shifts since the Early Holocene [SCA Proceedings - PDF]. Grenda, Jeffrey Homburg, Manuel Palacios-Fest, Steven Shelley, Angela Keller and Davis Maxwell Spatial and Temporal Distributions of Archaeological Heated-Rock Cooking Structures in the Transverse Mountain Ranges: Proposed Markers of Land-Use Shifts since the Early Holocene [SCA Proceedings - PDF].Definition of the base of the Pleistocene has had a long and controversial history.Because the epoch is best recognized for glaciation and climatic change, many have suggested that its lower boundary should be based on climatic criteria—for example, the oldest glacial deposits or the first occurrence of a fossil of a cold-climate life-form in the sediment record.
These criteria continue to be considered locally, and some workers advocate a climatic boundary at about 2.4 million years.From these studies, as well as studies of river terraces in the Alps, a chronology was developed that suggested the Pleistocene consisted of four or five major glacial stages which were separated by interglacial stages with climates generally similar to those of today.Beginning with studies in the 1950s, a much better chronology and record of Pleistocene climatic events have evolved through analyses of deep-sea sediments, particularly from the oxygen O), which is determined on calcium carbonate from shells of microfossils that accumulated year by year on the seafloor.The ratio depends on two factors, the temperature and the isotopic composition of the seawater from which the organism secreted its shell.Shells secreted from colder water contain more oxygen-18 relative to oxygen-16 than do shells secreted from warmer water.