INTERPRETATIONS OF GRAVITY ANOMALIES IN WESTERN NEW YORK STATE

Over 5,000 gravity measurements were made in western New York and Lake Ontario to produce a gravity anomaly map of the area. The area including the western and central part of New York at latitudes 42°N and 44°N and longitudes 76°W and 80°W. The area of investigation is shown on the Niagara and Finger Lakes sheets of the geologic map of New York. Within this area is the Clarendon-Linden fault, the most prominent structural feature in the Paleozoic rock in western New York. One thousand additional gravity measurements were made at 3.2 km intervals in the vicinity of the Clarendon-Linden fault.

The gravity map is dominated by gravity anomalies due to rocks of varying density in the Precambrian basement. The Precambrian crystalline rocks of the basement unconformily underlie the Cambrian, Ordovician, Silurian, and Devonian strata that dip southward less than a degree. The outcrop patterns of the Paleozoic rocks striking from east to west have little variation in density suggests the north-south trending gravity anomalies are due to the basement rocks and structures striking north-south.

The Clarendon-Linden fault lies along the western flank of a series of gravity highs observed to extend in north-south direction across Lake Ontario. These gravity highs are probably due to a series of mafic metavolcanoes that outcrop north of Lake Ontario and extend into western New York. Magnetic anomalies associated with the mafic metavolcanoes lend support to the interpretation. The geophysical data also suggest a fault that has a northwest branch near Attica, New York. This fault may account for the moderate seismicity between Attica and Buffalo. Several other interesting gravity anomalies occur in the area that may be related to seismicity and possibly geothermal energy in the area.