Foos, Annabelle M. and Szabo, John P., 2000, Clay mineralogy of Pleistocene deposits in North-central and Northeastern Ohio. 37 th Annual Meeting of The Clay Minerals Society Programs and Abstracts, p. 49

ABSTRACT

The clay mineralogy of Pleistocene deposits in north-central and northeastern Ohio generally consists of mixtures of illite, kaolinite and chlorite. The diffraction intensity ratio is used to estimate the relative abundance of these minerals (DI = 1.0 nm illite peak area divided by the 0.7 nm kaolinite and chlorite peak area). The clay mineralogy of tills generally reflects the source areas and flow paths of glaciers into Ohio during the Pleistocene. DIs for unweathered Illinoian and Wisconsinan tills of the Central Lowlands in north-central Ohio average between 1.3 and 1.5, comparable to those of the underlying Paleozoic bedrock. On the Allegheny Plateau DIs decline to less than 1.0 from incorporation of Pennsylvanian shales and underclays and weathered glacial deposits. A study near the Pennsylvania-Ohio state line suggests that 60% if the variance in clay mineralogy of a till unit was attributable to the clay mineralogy of the underlying bedrock along the flow path. Another study shows that some variance in clay mineralogy may be attributable to shales from a more distant source area. Analyses of weathering profiles show a progression from chlorite to vermiculite and from illite to an illite-smectite intergrade in the glacial deposits in Ohio. Sediments at Garfield Hts., Ohio record an episode of weathering and colluviation during the early or middle Wisconsinan substage. A blocky to massive, jointed, accretion gley fines downslope and contains pebble bands heavily stained with iron and manganese. X-ray diffractograms of this gley either show definable vermiculite, smectite, and illite-smectite peaks or very broad peaks of heterogeneous swelling material. Deposition of the gley is interpreted to have occurred in cyclical episodes as a Sangamonian paleosol was being eroded upslope.