Since the publication of the Glacial map of Ohio (Goldthwait, White, and Forsyth, 1961, U.S. Geological Survey Miscellaneous Geologic Investigations Map I-316), many workers have continued efforts to decipher the Quaternary history, geomorphology, and deposits of Ohio. This map of the Quaternary geology of Ohio attempts to consolidate this improved understanding of Quaternary geology in a uniform format for the entire state.Compilation ws begun by the late Dr. Richard P. Goldthwait, to whom this map is dedicated. Additional revisions and compilation of a series of 1:250,000-scale open-file maps (Ohio Division of Geological Survey Open-File Maps 291-300, 1993) were completed by staff of the Ohio Geological Survey, prior to preparation of this map. The individual maps used to compile this map differ widely in age, scope, and detail. Many areas of complex geology have been simplified to fit the scale and map units of this map. Refer to the data sources listed below for available maps that have more detail at a larger scale. The geological units on this map are grouped by age, depositional process, (water-deposited, ice-deposited, etc.), and geomorphic occurance (ground moraine, end moraine, hummocky moraine, etc.). For example, the most common unit in northeastern Ohio is G4, a Late Wisconsinan-age clayey till (Hiram Till) depositied as ground moraine.