NONGLACIAL SURFICIAL PROCESSES DURING THE EARLY AND MIDDLE WISCONSINAN SUBSTAGES FROM THE GLACIATED ALLEGHENY PLATEAU IN OHIO

A review of the literature suggests that nonglacial surficial processe s may be inferred from sites in Ohio of early through middle Wisconsin an age. These sites are not distributed uniformly and are identified b y baring post-Illinoian positions and nonfinite radiocarbon ages (that is, greater than 34,000 years). Organic deposits and paleosols of thi s age are comparatively common in the lowlands of southwestern Ohio, a nd the period is known to hare experienced both warm and cool climates because some deposits contain oak, ash, and beech fossils, whereas ot hers yield spruce. However, comparatively little evidence of this age has been found on the northwestern edge of the Allegheny Plateau in no rtheastern Ohio. One remarkable exception is a site in a gravel pit in Garfield Heights in Cuyahoga County. This site provides an extensive record of weathering, pedogenesis, colluviation, loess deposition, and cryoturbation from this time, and is cohere an accretion gley, derive d from an older paleosol, may have been deposited during the early Wis consinan substage. Cryoturbated loess overlying the gley has a minimum age of 27,000 years in its upper part; its pollen suggests a boreal c limate. An overlying loess, having a different provenance, was deposit ed from 24,000 to 27,000 years ago and contains pollen and insects tha t represent an open boreal environment. A finite radiocarbon date on w ood in sand and gravel from a depth of 74 m near London, Ohio, implies that fluvial baselevels were significantly lower before the late Wisc onsinan substage. A deeply entrenched drainage system may hare caused geomorphic instability of the landscape during this time and inhibited development and preservation of soils.