HIGH RESOLUTION MAGNETIC ANOMALY MAPPING AND BASEMENT STRUCTURE IN THE FINGER LAKES REGION, CENTRAL NEW YORK

Fracture systems and fault zones have been well documented in the Finger Lakes region of central New York, and earlier researchers have linked the surface structures to potential basement faults. The regional magnetic anomalies (USGS source) in the Appalachian basin are continuous with anomalies that occur in the Adirondack basement, concluding that basin anomalies are related to basement lithology variation and structures. A substantial low magnetic anomaly occurs in the central Finger Lakes region from Elmira, NY in the south to Lodi, NY in the north. This low anomaly is divided by an ENE trending high, and the eastern margin ends abruptly at Cayuga Lake. During this investigation, multiple high-resolution water-based magnetic anomaly surveys were completed on Cayuga Lake to examine the details of this anomaly transition. An Overhauser magnetic gradiometer and a Cesium magnetometer were mounted on an inflatable motorboat. Both magnetometers were set to collect continuous readings at a rate of 1 per sec, resulting in data points spaced about 5 m apart at full throttle. A suite of magnetic profiles collected span the width of Cayuga Lake between Trumansberg and Interlaken, and were spaced about 800 m apart. The magnetic anomalies are low when compared to the region, vary about 300 nT overall, with domains of low and high that span the width of the lake and trend ENE. The details of the anomaly maps are parallel to the regional trends and most likely reflect basement variations. It is interesting to note that the ENE trend in anomalies is continuous and nearly parallel with a major magnetic high anomaly that occurs over the southern Adirondacks and correlates with the Piseco Lake shear system. Small variations (10's of nT) in the magnetic profiles correlated in the N-S direction and most likely reflect variations in the Paleozoic strata beneath the lake.