Tuesday, 8 November 2005
12

Soils and Geomorphic Surfaces of Eastern Craighead County Arkansas.

Carrie Hawkins, University of Arkansas at Fayettevile, 911 W Hughes St. Apt 8, Fayetteville, AR 72701, E. Moye Rutledge, University of Arkansas, 104 Skyline, Fayetteville, AR 72701, Edgar P. Mersiovsky, USDA-NRCS/Soil Science, 700 W Capitol Ave/Rm 3416 Fed Bldg., Little Rock, AR 72201, Larry B. Ward, USDA-NRCS (retired), 115 PTSC, Fayetteville, AR 72701, and Doug A., Wysocki, NRCS-National Soil Survey Center, 100 Centennial Mall North, Lincoln, NE 68508.

The study area consists of about 500 km2 of the Eastern Lowlands of the Lower Mississippi Valley in Craighead County, Arkansas. The St. Francis River forms the east boundary of the study area with Crowley's Ridge on the west, and adjoining counties on the north and south. Our purposes are to gather and present information on soils and geomorphic surfaces within the area. We will emphasize geomorphic information because it is the first step in understanding soil distribution. Two major geomorphic surfaces exist in the area -- the St. Francis River Flood Plain and one or more loess-covered late Pleistocene terraces. Other landforms of secondary concern are liquefaction features and alluvial fans. Resources available include (1) 1917 soil survey, (2) 1979 soil survey, (3) Saucier's 1994 geomorphic map, (4) 10-m National Elevation Model and, (5) our lines. Our goals are to accurately define the Ridge-terrace and terrace-flood plain boundaries and then evaluate terrace number and distribution. The above resources are inconsistent in defining the Ridge-terrace division. Previous work considers both the Ridge and terrace(s) to be covered with Peoria loess. Thus, soils of the same age and composition exist on both the Ridge and terrace surfaces; Soil distribution alone cannot accurately define terrace boundary. Previous workers agree that the terrace-floodplain boundary is marked by an escarpment beginning near Bowman and extending north. From Bowman south, however, the escarpment fades and workers disagree on the geomorphic boundary. We propose deep borings (2-6 m) on transects to help identify the geomorphic surfaces: two across the Ridge-terrace boundary and one across the terrace-floodplain boundary. Next, additional transect(s) should be investigated to distinguish among terraces, if present. The 1979 Soil Survey on an aerial photo background and the 10-m National Elevation Model were especially helpful in our study.

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