<p> Northwestern Indiana has land surfaces and soils that are around 15,000 years old, resulting from sediments deposited from the Wisconsinan Glaciation during the late Pleistocene period. These geologically young soils exhibit depletion of base cations and low pH's (near 4.0) which are chemically similar to much older and more intensely weathered soils. We hypothesize that FeS2 (iron pyrite) within the shale fragments of the glacial deposits was oxidized upon exposure of oxygen near the earth's surface and resulted in naturally occurring acid sulfate weathering. To test our hypothesis, we isolated the area with ArcGIS, collected clast samples from gravel pits, utilized historic soils databases, and analyzed samples with X-ray diffraction to determine if associated properties and soil minerals would support acid sulfate weathering as the cause of the current soil chemical properties. Soil samples and glacial outwash cobble-sized clasts were collected and X-ray diffraction was used to determine the presence of pyrite or of pyrite weathering products jarosite and gypsum. Existing soil databases and lab data were examined to obtain further details of the occurrence of the potential acid sulfate weathering. A review of the geologic literature was also conducted to put the acid sulfate weathering processes into a landscape perspective and geologic context. The clast samples and some soil samples indicated the presence of jarosite and gypsum which are commonly associated with acid sulfate weathering. This research also found that ultic soil properties and low pH soils were associated with sandy glacial outwash and this information was displayed spatially. The sandy outwash has a lower CEC and lower buffering capacity when compared to nearby higher clayey glacial till. There was inferential evidence of acid sulfate weathering in calcareous glacial which is illustrated by iron oxide pseudomorphs. The lack of initial pyritic shale combined with the neutralizing potential for the calcareous till prevented these soils from developing ultic properties and low pH's. Additionally, this research assessed the potential for naturally occurring arsenic in the soils. Elevated arsenic levels were found in soils that occurred in the lowest part of the landscape. Understanding the process of naturally occurring acid sulfate weathering and associated elevated arsenic within this landscape will provide more information on use and management of these areas.</p>

<p> Few studies provide data that can document the long-term landscape evolution of the Piedmont of the southeastern United States. Here we present the results of field mapping and a soil chronosequence for fluvial terraces along a ~46 km reach of the Catawba River, NC and SC. Five terrace units (Qt1&ndash;5) have been mapped along the reach, and in certain regions a sixth surface (Qt0) was mapped. Observations of bedrock surfaces on Qt3&ndash;Qt0 confirmed that these units are strath terraces. Longitudinal profiles of terrace units constructed from mapping data revealed static channel convexities in Qt5&ndash;Qt1 in the lower reach of the study area at Landsford Canal State Park, and a lack of an obvious influence on terraces profiles within the Gold and Silver Hill shear zones in the middle reach. Age dating of terraces in this study included deriving ages based on surface height above the channel (Mills, 2000) and IRSL samples obtained from Qt3 exposures. Ages, reported in ka, are as follows: Qt0&mdash;4591 &plusmn; 404 ka, Qt1&mdash;1852 &plusmn; 365 ka, Qt2&mdash;1181 &plusmn; 194 ka, Qt3 (average of two IRSL ages)&mdash;142 &plusmn; 32 ka, Qt4&mdash;50 &plusmn; 8 ka, and Qt5&mdash;5 &plusmn; 2 ka. Up to 3 soil pits were dug on each terrace unit Qt5&mdash;Qt2, and soils described as per Birkeland (1999). Chronofunction trends of soil morphological properties include soil colors in the most developed B horizons reddening and clay films increasing in amount and prominence with surface age. Soil samples were analyzed for particle size, pedogenic iron (AAS), bulk density and major elements (XRF). Some of these analyses show expected trends with respect increasing surface age for terraces of the Catawba River, such as increases in clay content (%) and decreases in iron activity ratios in most weathered B horizons with increasing surface age. Overall the history Catawba River is one of five distinct periods of lateral planation of the valley, possibly driven by transitions to interglacial periods, punctuated by periods of incision, whose cause is currently unknown. The soil chronosequence, ages, and data derived from mapping, however, provide a strong foundation that can be used in further studies of the long-term landscape evolution of the SE Piedmont of the SE United States.</p><p>