2002 Denver Annual Meeting (October 27-30, 2002)

Paper No. 10
Presentation Time: 8:00 AM-12:00 PM


DURBIN, James M., ORR, Gregory and JONES, Ryan C., Geology, Univ of Southern Indiana, 8600 University Blvd, Evansville, IN 47712, jdurbin@usi.edu

The Patoka River is a unique stream in that it heads in the unglaciated uplands of south-central Indiana, before joining the White River a few kilometers upstream from the confluence with the Wabash River. Both the White and the Wabash Rivers were major outwash sluiceways during the Wisconsinan glaciations. This project reports on the preliminary data recovered from cores extracted from the alluvium and terraces in the lower 2/3 of the Patoka River valley. It is apparent from the available map, core and field observations that the unglaciated bedrock controlled parts of the valley recorded the same glacial and climatic history with fluvial morphology and stratigraphy unique to specific segments of the basin. In the middle unglaciated reach of the river, the stream constructed strath terraces, with a thin veneer of alluvium and/or colluvium in which soils have developed. In the lower reach of the stream terraces are not obvious, although buried paleosols are present at shallow depths within the alluvium. It is not apparent if there are multiple terraces and paleosols at this writing, or what was the exact timing of valley being cut and/or filled. The history of glacial meltwater flowing down the Wabash and White Rivers, when combined with substantially more alluvial fill suggests that the trunk streams acted as a local base level. As the glaciated rivers aggraded, the tributary floodplains did as well, at least in the lower part of the valley. The Patoka may have lacked clastic sediments and/or the stream power needed to construct terraces, and incise thick alluvial floodplains upstream from Jasper, IN. The climatic history of the region during the latest Pleistocene and the Holocene may be responsible, in part or total, for the development of the strath terraces in the upper and middle part of the basin.