GEOLOGIC INTERPRETATION OF GRAVITY ANOMALIES IN THE NORTHWEST ADIRONDACK LOWLANDS, NORTHERN NEW YORK

Closely spaced gravity measurements were made in the Northwest Adirondack Lowlands to construct a gravity map of the survey area. This map reveals local gravity anomalies related to the seismicity, geology, and faulting that are not seen on regional gravity maps. A gravity map of the area with the geology superimposed on the map reveals the correlation between the geology and gravity in the area.

In the western area of the map, a northeast-southwest trending gravity gradient parallels the trend of the Black Lake fault. This gradient separates higher density rocks in the east from low-density rocks in the west. Eastward from the gradient are small gravity lows over alaskite bodies and a gravity high over a gabbro pluton. On the south-central area of the map is a northeast trending elliptically shaped gravity high centered over the Sylvia-Lake Zinc District. Northward from the Sylvia Lake anomaly is a similar anomaly possibly related to the zinc deposits in the area. In the east, the gravity map shows a gravity gradient along the Carthage-Colton mylonite zone, with lower density rocks in the east from higher density rocks in the west. Several earthquake epicenters occur around the perimeter of circular shaped gravity high in this area.