Eastern United States loess mapped by the U.S. Department of Agriculture, National Resources Conservation Service (USDA-NRCS) mostly occurs near major river systems like the Delaware and Susquehanna Rivers. The proximity of loess along major river valleys suggests late-Quaternary glacial meltwater sediments were dominant sediment sources for loess. Based on differing lithologies of meltwater deposits in these systems, we hypothesize that loess in each river system has a unique geochemical and mineralogical signature. To test this hypothesis, we examined pedons developed in loess parent materials, and adjacent to either the Delaware or West-Branch of the Susquehanna River, both of which carried large amounts of Wisconsinan outwash. Soils were analyzed for particle size distribution, clay mineralogy, and coarse and fine silt particle density, mineralogy, and geochemistry. Results show that while the pedons are similar in morphology, substantial differences exist in the pedons' textures, mineralogies, and geochemical compositions. We attribute the differences to parent material differences that stem from lithologically distinct sediment sources for loess from the two river systems. Susquehanna River loess has a higher particle density, and lower abundance of minerals such as Zr, base oxides (such as CaO), and rare earth elements. Discriminant analysis results suggest that developing a “loess fingerprint” for each river system based on major, minor and rare earth elements is possible, and likely to be useful in differentiating sources; however coarse silts may be a more effective fraction (than fine silts) for sediment sourcing, especially if rare earth elements are used.
All Science Journal Classification (ASJC) codes
- Earth-Surface Processes