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Soil Survey Region 9 Staff Assist with SSSA Field Tour

By Region 9 Soil Survey Staff: Chance Robinson (Stephenville), Travis Waiser (Kerrville) and Wayne Gabriel (Temple)

In November, over 30 soil scientists from 18 states and countries participated in the “Soils and Landscapes of North Central Texas” field tour preceding the 2019 ASA-CSSA-SSSA International Annual Meeting in San Antonio. The tour was organized and led by NRCS soil scientists from the Stephenville and Kerrville MLRA Soil Survey Offices together with Texas NRCS staff, Soil Survey Region 9 staff, and Tarleton State University faculty.

The tour explored 10 unique soil landscapes across the extent of seven land resource areas in North Central and South Central Texas with a special emphasis on the interpretative significance of noncemented bedrock layers . Soil landscapes forming in mudrocks, sandstones, limestones, and granites of Cretaceous, Pennsylvanian, Ordovician, and Precambrian age were encountered during the trip. In the sub-humid and semi-arid climate of the southern great plains, slightly weathered mudrock layers are often encountered proximal to the surface in a dry moisture state. Excavation difficulty and water relationships of these layers is dependent on the moisture status. Weathering and persistence of these layers within 2m is dependent on the environmental factors of landscape position, bedrock depositional environment, and present soil climate. Mudrock layers have been inconsistently described as C, Cr, and Cd layers (paralithic and densic contacts, materials, and bedrock) in published soil surveys of North Central Texas from 1972 to 2009.

One of the overarching goals for the tour was to meet as a national (and international) group of soil scientists in the field to build understanding and consistency in the description of soft and weathered bedrock. In short, it is important that the soil science community meet together in soil pits to see what we see, discuss, and work toward consistency in the southern great plains, nationally, and internationally. Soil Survey Region 9 Staff have been working toward a consistent description of these materials since 1987. In the mid-1990s with the Soil Survey of Young County, Texas in MLRA 80B, these efforts toward consistency focused on noncemented soft sedimentary bedrock layers (Figure 3). With the Soil Survey of Mason County, Texas in MLRA 82A in the mid-2000s, efforts focused on consistency in describing soils forming in weathered igneous and metamorphic rocks. Soils such as the Voca series (Figure 4) forming in weathered granite present a different host of issues compared to the fractured sedimentary rocks which dominant the southern great plains.

On the final day of the tour the group visited a meteorite impact crater site and explored the hillslope created following the impact as well as several examples of petrocalcic horizons and degraded petrocalcic horizons forming in association with limestone and marlstone bedrock of the Edwards Plateau.

With the “official” tour completed, the group headed to San Antonio, still discussing, arguing, and defending what they saw. Conversations like these present many viewpoints which expand the understanding of the ever-changing soils.

Soil Survey Region 9 Staff Assist with SSSA Field Tour, By Region 9 Soil Survey Staff: Chance Robinson (Stephenville), Travis Waiser (Kerrville) and Wayne Gabriel (Temple), (2019, Dec)