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.

This study aimed to contribute to baseline knowledge of permafrost geochemistry within the uppermost 3-4 m of permafrost at 8 sites on the Peel Plateau and east of the Mackenzie Delta, NWT (67-68oN). The following variables were measured: gravimetric water content (GWC), pore water conductivity (PWC), leachate conductivity (LC), dissolved ions by ICP-AES (i.e. Ca, SO4, Mg, Fe, K, Na, Mn, Cl), organic carbon content (calculated by linear regression from organic matter content), as well as inorganic carbon content (obtained from loss on ignition analysis). PWC was positively correlated to GWC and values were generally at least 5 times less than LC values, likely underestimating total dissolved solutes using the former method. LC increased with depth to reach maximum values below the paleo thaw unconformity (>10 mS/cm). Carbon content typically remained low throughout the cores with the exception of samples associated to the shallow-rooted vegetation cover at the ground surface. Results showed that the active layer, relict active layer and the permafrost below the thaw unconformity can be divided into three statistically significant layers. PCA results indicated some spatial patterns with increasing LC values at greater depth, suggesting that layer geochemical profiles reflect varying degrees of soil chemical weathering processes since the early Holocene.

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