ANALYSIS OF SOIL DEVELOPMENT AS A FUNCTION OF AGE IN LITTLE CONNEAUTTEE CREEK DRAINAGE BASIN IN ERIE COUNTY, PA

The purpose of this study was to develop a soil chronosequence in an area with a relatively well-known depositional history to test the hypothesis that soil development is a function of age. Correlating soil development to the relative age of landforms may aid in the understanding of the depositional history of areas in which the geomorphic evolution is unknown. Previous studies have suggested that increased soil development is indicated by an increase in clay accumulation, rubification of the soil, development of soil structure, and the presence of stable clays.

A series of three terraces located south of Edinboro, Pennsylvania were examined to better understand soil development as function of age. The terraces are believed to be younger with decreasing elevation. Therefore, a post-incisive soil chronosequence should show a decrease in soil development with decreasing elevation. The soil was exposed in pits on each of the terraces, described, and trench sampled for laboratory analysis.

Terraces one and two are at elevations of 395 m and 384 m.a.s.l., respectively, and have till parent material. Terrace three, at 365 m ASL, appears to be a glacial outwash terrace. There appears to be no discernable trend in the clay accumulation or matrix rubification with increased age in the soils examined. The mottles, however, do become increasingly more red in hue with ascending elevation going from 10YR on terrace one, 10YR and 2.5YR on terrace two, to only 2.5YR on terrace three. The soil structure development and the relative amount of stable clays do show the hypothesized trend of increasing with age. The soil on terrace one and two have strongly to moderately developed soil structures, whereas the soil structure on terrace three is weakly developed. There are decreasing amounts of expandable clays and kaolinite with descending elevation.

Recent research on terraces at a lower elevation in the same stream valley also showed that soil development increased with age. Based on horizon development and soil depth, the older terrace was determined to have the most developed soil of the three terraces studied. Together the two studies confirm that soil development may be used to interpret relative age of landforms. However, several soil characteristics may need to be examined to accurately determine the relative development of the soil.