Accession Number:

ADA244257

Title:

Geophysical Investigations of an Anomalous Unfrozen Zone, Caribou Peak, Alaska

Descriptive Note:

Corporate Author:

COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH

Report Date:

1991-10-01

Pagination or Media Count:

29.0

Abstract:

Occurrence of unfrozen materials and groundwater flow on a north- facing slope in interior Alaska is important to recognize, both for predicting the spatial distribution of perennially frozen ground as well as for understanding watershed hydrology. An anomalous unfrozen zone or talik was located on the northern slope of Caribou Peak by drilling in April 1985. Impulse radar surveying of the area immediately adjacent to this drill hole, as well as one three transects upslope of its locations, revealed that the unfrozen zone is the result of groundwater flow in the bedrock along a relatively planar zone, interpreted as a fracture. This fracture and two others located by radar are continuous in the direction of the slope, trending generally N20 deg E and dipping about 9 deg east. Geologic logs indicate that the drill hole intersected a fracture in the bedrock, a quartz-muscovite schist, at a depth of about 8.5 to 9.0 m. Downhole measurements show ground temperatures at this depth are generally uniform and slightly above freezing throughout the year, suggesting continuous flow of groundwater within the planar structure. Analysis of the freezing point of the groundwater sample indicates normal freezing beginning at 0 C, while ion chromatography indicated that the water was fresh and not highly mineralized. Vegetation patterns, coupled with the borehole location and fracture orientation, suggest that flow originates within the upper and central parts of the peak and discharges into the valley of Poker Creek.

Subject Categories:

  • Hydrology, Limnology and Potamology
  • Snow, Ice and Permafrost

Distribution Statement:

APPROVED FOR PUBLIC RELEASE