MINERALOGICAL INVESTIGATIONS OF WETLAND SOILS DEVELOPED IN A DISTURBED LANDSCAPE OF AN EMERGENCY SPILLWAY AT CAESAR CREEK STATE PARK, SOUTHWEST OHIO
Soil material from three small wetlands that have developed in an emergency spill way at Caesar Creek state park that was constructed in the early 1970’s was investigated to determine the nature of mineral composition. This spillway was cut in the Upper Ordovician Liberty and Whitewater formations which are comprised of shallow marine limestone and shales. Samples of shale and limestone, including limestone with oxidized pyrite were investigated for comparative purposes.
Powder X-ray diffraction indicates that bedrock limestone is composed dominantly of calcite and ferroan dolomite and that shale is dominated by illite with lesser amounts of chlorite and kaolinite. Mineralogy of the clay fraction of wetland soils are also dominated by illite with lesser amounts of chlorite and kaolinite. Basic transmission electron microscopy (TEM) investigation of soil minerals supports X-ray diffraction data in that illite is the dominant mineral present. Illite occurs as euhedral to subhedral crystals and aggregates. Poorly crystalline Fe-oxides are common and are found as irregular aggregates commonly several tens of nanometers in diameter and are often intimately associated with illite particles. Euhedral crystals of apatite approximately 200 nm in length are common in the soil fraction. Spot energy dispersive spectroscopy (EDS) techniques indicate that phosphorous is associated with illite.
XRD and TEM indicate that major transformations of phyllosilicate minerals in incipient wetland soils do not occur in such settings over periods of a few decades. However, poorly crystalline iron oxides are common and appear to be intimately associated with illite in some cases. Illite appears to have a significant role in the sorption of phosphate and minerals may play a large role in controlling nutrient dynamics in soils of incipient wetlands .