Silty Deposits of a Low, Pleistocene‐age Terrace in Eastern Arkansas

Abstract

AbstractA segment of Terrace Qtb3 of the Western Lowlands of Arkansas was transected to determine if the silty material capping the terrace is loess or silty alluvium. Four sites along an east‐west transect were sampled to test the hypothesis that the material is loess with its source area immediately east of the terrace segment. Three deposits dominated by silts were identified at each site by morphology, fine‐earth and clay‐free particle size distribution, and by distribution of total Ca and K in the coarse silt fraction. The lowest of the silty deposits was identified as alluvium by its sand contents and stratification in the lower part. The morphology of the upper two deposits was similar to that of loess on other terraces in the area. However, relationships between clay‐free particle size distribution and log distance from the proposed source area were not those expected for loess. Thus, these two deposits are also interpreted as silty alluvium. Geomorphic relationships indicate that the terrace is younger than Illinoian, but no minimum age can be deduced from current data.