Semi-quantitative analysis of the clay mineralogy of a 70 m deep core taken at the Calhoun Critical Zone Observatory (CCZO) (Bacon et al., 2012) show an upward transition from chlorite, smectite, I-S mixed-layer, and weathered mica to kaolin group, K-I mixed-layer, and weathered mica between 18 and 27 meters. Near the surface (<10 m), there is a further transition to kaolin group, I-V mixed layer, K-S mixed-layer, K-I mixed layer, HIV, and weathered mica.
Austin, J.C. (2016): Clay mineralogy of the deep core. Calhoun CZO 2016 Summer Science Meeting, Clinton, SC.
This Paper/Book acknowledges NSF CZO grant support.