Quaternary geology of the Appalachian Highlands and Interior Low Plateaus
The Appalachian Highlands consist of the Piedmont, Blue Ridge, Valley and Ridge, and Appalachian Plateau physiographic provinces (Fenneman, 1938) (Fig. 1). The Interior Low Plateau province is also included with this discussion of the Appalachian Highlands. The Quaternary geology of the unglaciated Appalachians is challenging because of the complexity of its montane landscapes and limited datable deposits. Surficial deposits in the Appalachians are difficult to date by radiocarbon because of relatively low sedimentation rates that, together with a high oxidation rate, result in poor preservation of organic material except below the water table. Only a handful of numerical dates older than late Wisconsin exist from deposits of alluvium and colluvium. Moreover, alluvial terraces, as well as colluvial deposits, are generally discontinuous in distribution, poorly exposed, and have considerable soil and vegetation cover, hindering reliable stratigraphic and morphologic correlation. Beyond the range of radiocarbon dating, correlation is even more tentative owing to postdepositional erosion and dissection of geomorphic surfaces, and to the lack of numerical-age-dating techniques applicable to these surficial deposits. Tephra are unknown.
Knowledge of late Quaternary climatic changes in the Appalachian region, from palynological study and radiocarbon dating of lacustrine and peat deposits, is relatively more advanced than stratigraphie investigations. Sinkholes formed in carbonate terrains provide continuous paleoenvironmental and paleovegetation records extending back through middle Wisconsin time. This paleoecological knowledge provides a tentative framework for interpreting landscape development during the Quaternary. However, well-dated palynological sequences from lacustrine sites commonly cannot be correlated directly with nonlacustrine
Figures & Tables
Includes 5 topical chapters covering paleoclimates, dating methods, volcanism, tephrochronology, and Pacific margin tephrochronologic correlation, and 15 chapters of regional synthesis covering: the Pacific margin; the Columbia Plateau; the Snake River Plain; the major pluvial lakes of the Great Basin; the Basin and Range in California, Arizona, and New Mexico; the Colorado Plateau; the Southern and Central Rocky Mountains; the Northern and Southern Great Plains, Osage Plains, and Interior Highlands; the Lower Mississippi Valley; the Gulf of Mexico Coastal Plain and Florida; the Appalachian Highlands and Interior Low Plateaus; and the Atlantic Coastal Plain. A large, full-color geologic map of the Quaternary deposits of the Lower Mississippi Valley, in addition to correlation charts, tables, and cross-sections relating to other chapters, is also included.