GEOLOGIC INTERPRETATION OF GRAVITY ANOMALIES NEW YORK SATE

A gravity map of scale 1:1,000,000 is constructed so it can be overlain over the recently published New York State Geologic Map Educational Leaflet 33 so the regional gravity anomalies may be compared with the bedrock geology. The gravity map of New York shows an excellent correlation of regional gravity anomalies with geology in New York. Seven areas show a correlation with geology but have some uncertainties in the interpretation.

A prominent gravity low mapped by Simmons occurs over the anorthosite in the northern Adirondacks. This low is interpreted as due to the low density of the anorthosite massif. Modelling indicates a slab with two roots account for the gravity anomaly.

North of the anorthosite is a series of circular shaped gravity highs extending northwestard across the northern Adirondacks into Quebec, Canada. These gravity highs correlate with most of the epicenters in northern New York and are probably related to the earthquakes in the area. The sources of the gravity highs are covered with younger Paleozoic rocks.

In southeastern NY, the elliptical shaped Scranton gravity high extends from Albany, NY to Harrisburg, PA. This anomaly is due to a dense mass deep within the crust. The geologic interpretation of this anomaly is uncertain.

In western New York, a series of gravity highs extends northward along the Clarendon-Linden Fault into Lake Ontario. These gravity anomalies are probably due to high-density mafic metavolcanoes in the PreCambrian. The Clarendon-Linden fault is probably related to these anomalies.

Finally, a gravity low occurs over the Tug Hill Plateau. This low is due to low density Precambrian basement rocks at depths that have been uplifted to form the gravity low.