Progress on a gravity map of Alaska

Abstract

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.

Gravity Anomalies Seaward of Deep-Sea Trenches and their Tectonic Implications

“…Gravity anomaly profiles across island arcs have been published by Gainanov (1955), Hayes & Ewing (1970), Segawa (1970) and Talwani (1970). In addition, land surveys of the Aleutian Arc (Woollard & Rose 1963;Barnes 1969;Carr et al 1971) and the Japan Arc (Tomoda et al 1970) have been published. La Coste Romberg gravimeter is a gimbal mounted meter (La Coste & Harrison 1961) and the Japanese T.G.S.G.…”

The United States Geological Survey in Alaska: Accomplishments during 1977

“…Two short offsets perpendicular to our line of traverse show a pronounced gradient (3-5 gammas/km) decreasing to the southwest, in apparent agreement with the regional map. The Bouger gravity map of Alaska (Barnes, 1976) shows that the regional gradient in this area decreases southeasterly, in the same direction as our profile. Although analysis of the data is still incomplete, inspection of the profiles shows little response to the outcropping basement rocks and few significant anomalies elsewhere.…”

“…The most recent Alaska gravity map (Barnes, 1976) shows that the Okpilak batholith is characterized by a prominent gravity low. The well is located on the edge of a gravity low enclosed by the 20 milligal contour.…”

“…In the Chandalar quadrangle, several linear features correspond to geology (Brosge and Reiser, 1964), geophysics (Cady, 1978;Barnes, 1976), and mineralization (DeYoung, 1978). One lineament and two interlineament zones seem to form boundaries for numerous rock types.…”

Stratigraphy, structure, and economic geology of the Iliamna Quadrangle, Alaska

“…The south shore of Kamishak Bay is a major indentation 95 km long in lower Cook Inlet that strikes nearly transverse to the structural grain of the bedrock and is reflected by a weak gravity anomaly (Barnes, 1976). Projected westward, this line intersects Big Mountain, and five vents fall on or near it.…”