Massive Ice and Ice-Rich Soil Detection by Gravimetric Surveying at Dry Creek, Southwestern Yukon Territory, Canada

摘要

Gravity measurements were made using a Scintrex CG-5 Autograv gravimeter in permafrost terrain conditions where bodies of buried ice were expected. The main objective was to assess the feasibility of using gravimetric technology to detect massive ice bodies at Dry Creek, Yukon Territory, Canada. Tests at 11 gravimetric survey lines and 10 boreholes were performed during the summers of 2013 and 2014. Residual anomaly profiles provide a quick first estimate of the amount of ice in underlying soil strata. A mean anomaly of-0.10 mGal was found near a thermokarst, south of the Dry Creek rest area along the Alaska Highway. The cryostratigraphy comprises at depth an ice-rich diamicton covered by massive ice with suspended silty inclusions and an overlying layer of glacio-fluvial gravel. At the base of a small glacio-fluvial hill deposit, on the southeast side of the road, a mean anomaly of-0.260 mGal was found. A massive ice body of 9.3 m of maximum thickness was drilled through. Since drilling is planned after gravimetric surveys, it is possible to assess whether or not this technique is effective for detecting sub-surface ice features. This paper presents an overview of the site, the gravimetric detection technique employed, and gravimetric and borehole test results and analysis.