Center for Earth and Environmental Science
Indiana University ~ Purdue University, Indianapolis

GEOLOGIC SETTING

Early settlers described the area where the project site is located as a low marshy area. Where Fall Creek had meandered back and forth across at its confluence with the White River a marsh complex had formed. Frequent flooding in the area led to Fall Creek being channelized and rerouted to the north of the present 10Th Street Bridge. Most of the area of the IUPUI campus including the project site was also filled over time. A 1941 air photo of the campus area shows the north end of the site shows the area was still being filled at that time. The biggest changes followed the disastrous flood of 1913. Photographs taken after the 1913 flood illustrate that the floodplain in the area of the project site was substantially reshaped during the levee construction following that flood (Figure 2). The soil type on the floodplain is listed as urban land - Genesee complex (Sturm and Gilbert, 1978). This complex includes about 40 percent urban land, and 40 percent well drained Genesee soil. Small areas of very poorly drained Sloan soil, somewhat poorly drained Shoals soils and moderately well drained Eel soils, as well as some areas of fill are also found in this complex (Sturm and Gilbert, 1978). This complex of soils, common on bottomlands in central Indiana, creates the mosaic of habitat types common on naturally functioning floodplains. In a naturally functioning system the east bank would now be a depositional environment, but reduced water levels and a dam just north of the site have reduced the available sediment supply. Broken glass found during preliminary investigations indicates that human influenced sediments extend to a depth of a least 1-m at the site. Slag was also found in two test holes at a depth of approximately 60-cm. The presence of slag in two locations several meters apart at the same approximate depth suggests that there may a stream deposited layer of slag in the area. Further work is required to determine how continuous this unit is and what its long-term implications might be. Details of the well logs are in Appendix C.

A small, ~ 2.5 acre, riparian wetland complex has formed at the north end of the project area, just south of the 10th Street bridge. The north end of the wetland formed as a sandbar was either colonized or planted with black willow, stabilizing the bar and allowing other species to develop (Figure 3). The interior of the wetland is a seasonally fluctuating emergent wetland with a small area of exposed mud flat. The variety of wetland types occurring in such a small plot makes this small section of the floodplain extremely valuable as a seed source contributing to the overall biodiversity of the area. Descriptions of two cores from this area are in Appendix D.
 

Center for Earth and Environmental Science
 School of Science
 Indiana University~Purdue University, Indianapolis
 723 West Michigan Street, SL118
 Indianapolis, IN 46202
 www.cees.iupui.edu
 cees@iupui.edu