Whole and Partial Clast Solution and the Impact on Interpretation of Morphological and Chemical Change over Time in Petrocalcic Soil Horizons.

Late-stage petrocalcic horizons hold a record of land surface modifications induced by climate change and tectonic events. This record is contained in the morphological and mineralogical attributes that are unique to these types of soils. The current configuration of pedogenic minerals and morphologic features in Mormon Mesa, Nevada petrocalcic horizons is the result of several million years of development. Ongoing work into the Mormon Mesa soil seeks to closely correlate pedogenic features and minerals to distinct climate events. Several gravel-rich, early Pleistocene(?) soils adjacent to Mormon Mesa may provide a snapshot into the development of late-stage pedogenic features and mineralogy in older soils like Mormon Mesa. Interestingly, these younger soils contain discrete macro-voids that either 1) cut through both matrix materials and detrital clasts, or 2) occur isolated in clasts with no alteration of surrounding matrix. Few voids contain white calcite that partially fills the upper portions of the cavities. The presence of these voids and infilling materials indicates post-induration soil solution chemistry changes and they are critical in understanding the chemical evolution of these horizons over time. Whole and partial clast solution may affect our interpretation of the features used to describe and relate late-stage petrocalcic soils to climate events.