GRAIN WEATHERING INDICES IN RIVER TERRACE STUDIES

Conventional determination of chronosequence age relies on technology that is generally expensive and can exceed the budget of short term research projects. This study integrates a semi-quantitative method with low cost tools in an attempt to correlate river terrace soil chronosequences without traditional dating techniques such as carbon or luminescence. Quartz grains from the soil in three sets of terraces along the James River between Lynchburg and Howardsville and one suite of five terraces on the Congaree River in the Congaree National Park were selected. The quartz grains were sampled via hand augering then prepped and reviewed under the Scanning Electron Microscope (SEM). The study utilizes a semi-quantitative weathering scheme, which calculates a score based on various mechanical and chemical weathering characteristics observed on the quartz grain under the SEM. Results have shown that while there is not a clear correlation of terraces between different sets, the weathering scheme is capable of correlating the relative ages of terraces within a set. This variability in weathering scores between sets of terraces indicates the complexity of factors that can enhance or mitigate chemical or mechanical weathering on quartz grains.