Progress on a gravity map of Alaska

The U.S. Geological Survey began gravity surveys in Alaska ten years ago with local surveys in the Copper River and Tanana Basins. Shortly before the 1963 AGU gravity symposium [Barnes, 1965], the emphasis shifted from local surveys to the preparation of a reconnaissance gravity map of the whole state with a 10-mgal contour interval on a scale of 1:2,500,000, which would be similar to the gravity map of the United States [Woollard and Joesting, 1964]. Data have now been obtained in approximately three-fourths of the state, but there are large variations in both station density and geologic usefulness of the coverage. The amount of coverage is primarily influenced by the distribution of water bodies because more than three-fourths of the stations have been obtained by riverboats, small skiffs, and floatplanes.