Date of Award

2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geography, Geology, and Anthropology

Abstract

Climate, tectonics, and drainage-basin characteristics dictate the conditions that control the discharge and sediment dynamics of rivers in continental interiors. Fluvial-system response and a partial human record have been recorded in valley landscapes. Regional patterns in the timing of sedimentation in the present day Midwestern United States have been recognized in several case studies throughout the region. However, there is much more that can be done to better understand climate change and climate responses in the region and particularly along the Wabash River in Indiana and its tributary streams. This study focuses on the Late Wisconsin and Holocene landscape change at two locations along the Brouilletts Creek in Vermillion County, IN and Edgar County, IL. The purpose of this study is to define allostratigraphic units for the Brouilletts Creek flood plain. The units have been used to reconstruct the local landscape changes. A comparison of the local changes have added to the identification of global and regional changes in the environment reflected in the geologic units. A buried site potential model has been constructed by analyzing the age and depositional environments represented in allostratigraphic units. The buried site potential model provide information about possible site locations and how and where people may have utilized the changing landscape. Five cores were taken at each of the study sites on transects that lay perpendicular to the channel. In most cases, depressions and high points were chosen as core locations. The cores were analyzed for color, texture, ped structure, grainsize, soil organic matter, magnetic susceptibility, and four organic samples were taken for radiocarbon AMS dating at International Chemical Analysis, INC. Four allostratigraphic units/subunits were identified and compared to previously described regional sediment units. Historic overbank and point bars, Historic alluvial fans, Late Holocene overbank and point bars, and Early/Middle overbank and bar deposits were all found within the stream valleys of Brouilletts Creek and South Fork Brouilletts Creek. A number of buried soils were discovered in solid cores based on color, ped structure, and grainsize change. The valley has substantial Late Holocene and Historic components. The Historic component is attributed to sedimentation due primarily to coal mining in the uplands north and south of the Brouilletts Creek. The late Late Holocene deposits (part of the Hyatt Island member) date to 340 ± 30 years RCYBP. This unit is most likely to the latest pulse of sediment in the cyclical soil/sediment cycles that have occurred about every 2000 years throughout the Holocene. Based on the known age of the sediment in the stream valley and based on the buried site potential model which was created in ArcGIS, there is little potential for buried materials within this stream valley. Those materials that are buried are Late Holocene in age and most likely historic or just pre-contact era. A surface site potential model was also created considering all the characteristics that are typical of known surface sites which are mostly Riverton and Mississippian in age. The model shows that there is some potential for surface sites to exist along the uplands just adjacent to the stream valley, as well as on outwash islands and stream terraces.

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