SEDIMENTOLOGY AND GEOCHRONOLOGY OF HOLOCENE PALEOCHANNEL FEATURES IN THE LOWER OHIO RIVER VALLEY, INDIANA

Rivers condition human settlement strategy by determining both the location of aquatic resources and the stability of the landscape. Therefore, understanding where the river was and how quickly it migrated in the past aids in predicting buried site potential. This study investigates the sedimentology and geochronology of paleochannel deposits along the Lower Ohio River floodplain. A series of low, wide swales are prominent features in a series of bottoms in a ~40 km section of the river valley downstream from the Falls of the Ohio. Previous studies in Knob Creek Bottom indicate that one of these paleochannel swales was active during the early Holocene, roughly 10K to 7.4K rcybp. The positioning of the others suggest that they are the remains of a single channel that flowed on the west side of the river valley during the early Holocene. To test this proposition, cores were collected in several locations within and adjacent to prominent swales. The channel is characterized by laminated point bar deposits overlain by overbank sediment containing a heavily weathered Alfisol or Mollisol soil with prominent redox mottles. The sediment ranges from silt to silt loam. In some reaches, alluvial fan sediments interfinger with the point bar deposits. Datable organic carbon was found in both point bar and overbank contexts. This study compares the sedimentology, weathering, and age of these channel segments to determine their geomorphic relationship.