Thin section and heavy mineral analyses of glacial till from northeastern Ohio and northwestern Pennsylvania show striking variations in texture in different stratigraphic units and in different sedimentary facies. Microstructures occur in sandy tills as well as in clay tills. Rock fragments in the tills are principally quartzite, sandstone, siltstone and shale, limestone and dolomite, and "crystalline" rocks. Quartz is the most common mineral fragment present. The most common heavy minerals, in approximate order of abundance are: clino-amphibole, magnetite, garnet, pyrite, clino-pyroxene, ortho-pyroxene, kyanite, tourmaline, apatite, zircon, sphene, rutile, and epidote. Quantitative data indicate successive reworking of older tills by younger tills.

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