In the recently discovered Prudhoe Bay field on the North Slope of Alaska the upper part of the production wells penetrates a massive permafrost zone. The base of this zone gets deeper as the distance from the existing seashore increases, the greatest depth so far found being about 2,000 ft. The extent of the permafrost zones may be seen quite clearly on logs run in the hole prior to casing, provided the hole diameter is not too large. The best definition can be obtained from the sonic, resistivity, and caliper logs. In addition, temperature surveys run in the completed wells several months after completion show clearly the base of the permafrost, and the different thermal conductivity of the frozen and unfrozen material.

Soils and geologic data have been obtained from a continuous core of the permafrost zone in the Prudhoe Bay area in the interval from 500 to 1,850 ft, and from several cores taken in parts of the upper 500 ft. A wide range of measurements has been made including densities and relative densities, porosities, ice saturations, and soil and ice classifications. From the results of these and other studies some comments and speculation on the deposition of the permafrost and the general geology of the surface deposits can be made.

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