Date of Award
Master of Science (MS)
During the summer of 1966, eighteen soil profiles on a series of 21 lateral moraines, were studied to ascertain the relationship of time to soil development. The moraines are located on Charlotte Ridge on the south margin of the Martin River Glacier in south-central Alaska. The elevation of the highest moraine is approximately fifteen hundred feet and is located 800 feet above the present level of the glacier.
To determine the direct effect of time on soil formation, the remaining soil forming factors were kept constant; the soil pits were located so that relief, exposure, and vegetation of the sites were as similar as possible. Till, rich in variable amounts of basalt, granodiorite and metamorphic rock, composed the moraine sediment. The climate of the region is cool maritime but microclimatic differences may be important for the ridge as a whole.
Field results indicate that a mature podzolic soil has developed on the upper 14 moraines, whereas the lower 7 moraines are characterized by a regosol. Samples of the soil horizons were collected for laboratory analysis.
The analyses for total carbon, carbonate carbon, organic carbon, nitrogen and particle-size distribution support the field descriptions and also confirm the major difference in soil development between the fourteenth and fifteenth moraines.
Lateral variation of the soil profiles along single moraines is minor. The increase in the abundance of cobbles in the till of the older moraines sharply increases the permeability of the till, thus increasing the depth of the soil profile. This variability in cobble distribution is the main factor affecting the minor soil profile differences on the older moraines.
No absolute date of formation exists for the older moraines, but tree-ring analysis indicates that the youngest two moraines formed in 1910 and 1700-1800, respectively. A core of a large spruce tree immediately upslope from the 1700-1800 year old moraine indicated the tree was at least 407 years old. But, the core penetrated only about half-way to the center of the tree revealing a probable age of about 800 years. Any further conclusion on the age of the older moraine must wait until datable material is found in the moraine sediment.
The study of the relationship of time to soil development on the till of Charlotte Ridge indicates a significant time interval between the fourteenth and fifteenth moraines. Other significant differences in age or a gradational sequence in age of the 21 moraines is not apparent from the analysis of the soil development.
Tinker, John R. Jr., "Time and soil development on lateral moraines, Martin River Glacier, south-central Alaska" (1967). Theses and Dissertations. 298.