MORPHOMETRIC ASSESSMENT OF LITHOLOGIC CONTROLS ON DRAINAGE-BASIN EVOLUTION IN THE CRAWFORD UPLAND, SOUTH-CENTRAL INDIANA

The Crawford Upland, located in south-central Indiana, is underlain primarily by clastic sedimentary rocks with a general west to east increase in the areal percentage of exposed carbonates. Associated with spatial trends in bedrock lithology are changes in landform morphology and landform assemblages. These changes have been quantified using principal components analysis on data measured from United States Geological Survey 7.5′ topographic maps for 105 small (<10 km2) drainage basins. The analysis suggests that morphometric parameters reflect adjustment to the lithology underlying drainage basins as well as the extent of solutional modification of carbonates by karst processes. Low order catchments underlain predominantly by clastics exhibit an erosional history that varies systematically with distance from the Ohio River. In contrast, basins developed in Mississippian carbonates exhibit a complex erosional history possibly related to resistant siliceous strata and local base level controls imposed by nickpoints. Cluster analyis was used to separate the 105 basins into five groups on the basins of basin morphology. -from Authors