CHRONOLOGY AND EXTENT OF GLACIATION IN WESTERN NORTH AMERICA AND LATE PLEISTOCENE PALEOECOLOGY

The extent, distribution, and timing of Late Pleistocene glaciation in western North America can be inferred from stratigraphic sequences, geomorphic features, and chronometric measurements. Consequences of glacial advance and melting are reflected by changes in geologic processes as well as the landscape-habitats available for biotic communities. Geologic evidence of environmental conditions along the Pacific coast and the southern margin of the Cordilleran ice sheet, along the eastern front of the Rocky Mountains and adjacent Great Plains, and in the glaciated mountains and lake-filled basins south of the continental ice sheets can be related to fossils and artifacts associated with the time before, during, and after the Last Glacial Maximum. Non-glacial conditions prior to the Last Glacial Maximum are partly reflected by radiocarbon-dated remains of mammoths and other mammals, while late glacial contexts associated with the Allerod and Younger Dryas intervals are associated with extinct fauna as well as Clovis and Folsom artifacts. The temporal and physical patterns of geomorphic processes influenced the habitats associated with Rancholabrean fauna including Pleistocene human populations. Geologic processes also influenced the preservation and visibility of paleoentological and archaeological contexts. Interpretation of the stratigraphic and chronologic geologic framework is critical to understanding paleoecological relationships between physical landscapes and biota, including adaptations by Late Pleistocene human populations.