IMPROVED INTERPRETATION OF HOLOCENE LANDSCAPE AND CLIMATE CHANGE IN THE BROUILLETTS CREEK VALLEY WITH CARBON DATING

Despite Indiana’s interesting and long geologic history, not much has been done in the way of determining the sequences related to the state’s longest river, the Wabash. The Wabash River acted as a major sluice way for the Wisconsin glacier during the LGM. The valley and its tributary valleys have been greatly influenced by glacial deposits and subsequent alluvial, colluvial, and Aeolian deposits. In order to understand the sedimentation and the soil formation within the drainage basin, it is important to begin research in smaller tributary valleys. In this study, descriptions for the allostratigraphic units along Brouilletts Creek and South Fork Brouilletts Creek. A site upstream from historic coal mining and a site downstream were selected to test the influence of change. Soil/sediment descriptions and units were described for the valley using USDA standards. Samples were tested for magnetic susceptibility and loss on ignition in order to assist in the identification of A horizons. Previous interpretation attributed the lower sedimentation to late Wisconsin deposition. With radiocarbon dates extracted from three different units, it is now understood that there was a Late Holocene sediment/soil cycle that created the units that are now overlaying glacial material. Earlier materials are no longer stored within these units along the Brouilletts Creek, but have been found within the Wabash River Valley. After greater influence of settlers and agriculture in the 1800s and later coal mining in the 1900s, sedimentation increased and appears to have come in two fluxes corresponding to these different anthropogenic changes. Further research within this valley and others are needed to understand how tributary valleys have influenced the main channel of the Wabash River Valley. Future investigation may be done in order to understand the timing of the sedimentation after coal mining began in the Brouilletts Creek Valley.