Abstracts Biological Sciences

Carbon-14 as a Tracer of Soil Movement in Earth Hummocks: A Case Study From Northwestern Arctic Canada

by Brittany Main

Involuted soil horizons and buried organic matter in the active layer and near-surface permafrost provide evidence that soil movement or cryoturbation is occurring within the active layer in hummocky terrain. Cryoturbation in the active layer of permafrost-affected soils could have significant implications in sequestering carbon, including trace metals and contaminants that are absorbed onto organic matter. Though several hummock development theories exist, there has thus far been limited evidence to support them; similarly, few studies have been able to establish hummock age. This study aimed to contribute radiocarbon-dated ages of buried organics in both the active layer and permafrost, as well as provide evidence for the convective cell/equilibrium model and the collapse model. Trenches were dug along a transect at two well-developed hummock sites in the Mackenzie Delta near Inuvik, NWT. Active layer and permafrost samples were analyzed for distribution of gravimetric water content (GWC), organic matter, inorganic carbon, and carbon-14 (C14). Results determined material ranged in age from the modern period (1959-1987AD) to 2300 yr BP with a generally normal distribution. Buried organics within the active layer ranged from 557-670 yr BP and 1023-1240 yr BP, with average displacement rates of 0.43 mm/yr and 0.16 mm/yr, respectively. These results suggest the convective cell/equilibrium and hummock collapse models can function simultaneously.