Richter et al., 2017

Talk/Poster

Gilbert's soil production paradigm applied to a critical zone's fractionation of particle sizes

Richter, Daniel deB., Jason Austin, Robert S Anderson, Allan R Bacon, Susan L Brantley, Zachary Brecheisen, Paul A Schroeder, Anna Wade, W. Steven Holbrook, Virginia Marcon, Aaron Thompson (2017)
American Geophysical Union 2017 Fall Meeting, New Orleans, Louisiana, 11-15 December 2017  Cross-CZO

Abstract

In 1877, Gilbert stated with wonder, “Over nearly the whole of the earth's surface, there is a soil, and wherever this exists we know that conditions are more favorable to weathering than to transportation.” Today, Gilbert's soil production function serves as a paradigm of critical zone evolution. We apply the paradigm to coarse over fine (COF) textured soils found in many lithologies and climates, soils typically attributed to lessivage, to fine clays hydrologically moving from A to B horizons. While not denying lessivage, we consider particle size fractionation in response to Gilbert's soil production treadmill at the Calhoun CZOs 70-m deep borehole. Feldspars weather to sand- and silt-sized kaolinite between 30 and 3m, a dissolution we attribute to biota's CO2 and carbonic acid, but between 3 and 1m kaolinite is comminuted to clay-sized micelles that astoundingly increase from 5 to 50% by mass. Lessivage also concentrates clay-size kaolinite that also ensures that quartz sand totals 80% of A and E horizons in the upper 0.5m. We hypothesize that as sand and silt-size kaolinite is fed into the B horizon by the soil production treadmill, biologically mediated stresses from bioturbation comminute sand- and silt-size kaolinites. We further suggest that most COF soils are coarse over fine over coarse textured soils, all based on Gilbert's soil production paradigm.

Citation

Richter, Daniel deB., Jason Austin, Robert S Anderson, Allan R Bacon, Susan L Brantley, Zachary Brecheisen, Paul A Schroeder, Anna Wade, W. Steven Holbrook, Virginia Marcon, Aaron Thompson (2017): Gilbert's soil production paradigm applied to a critical zone's fractionation of particle sizes. American Geophysical Union 2017 Fall Meeting, New Orleans, Louisiana, 11-15 December 2017.