USING MULTIPLE GEOPHYSICAL TECHNIQUES TO STUDY DRUMLIN DEPOSITS IN CENTRAL NEW YORK

Drumlins can vary in shape, size, internal composition and structure. Mapping variation in size and shape is readily done using digital elevation models, topographic maps, aerial and satellite images. However, mapping internal details of drumlins without the use of boreholes is hampered by forest and agricultural cover, and few natural exposures. During this investigation, two drumlins with different morphology located in central New York were surveyed using several geophysical techniques to better understand the distribution of sediment type and groundwater: magnetics, electrical resistivity, induced polarization, electromagnetics, and ground penetrating radar. In general, the drumlin deposits have a narrow magnetic anomaly range of approximately 100 nT, with higher anomalies associated with sand and gravel derived from crystalline basement, and lower anomalies associated with regions dominated by clay deposits. This is especially apparent on the margin of the drumlins where they are surrounded by glacial lake varve deposits. The anomaly maps reveal systematic variations that appear to correlate with elevation on one drumlin suggesting that it may be stratified. The apparent stratified nature of one drumlin also correlates with low (<150 ohm-m) and high (>300 ohm-m) electrical resistivity anomalies observed in multiple parallel surveys. ERT anomalies for the second drumlin are inconsistent, but high and low domains appear to correlate with the magnetic anomalies. The induced polarization surveys revealed regions dominated by clay deposits, but revealed little detailed information for the internal structure of both drumlins. Finally, six GPR profiles were completed across both drumlins, and through the transitional into the adjacent glacial lake varve deposits. The first drumline, that appears to be stratified based on other techniques, produced GPR profiles with simple internal structure. But, profiles for the second drumlin show apparent dipping lenses of varying sediment, with some strong reflectors showing apparent offset due to small faults. During this presentation, we will show the detailed results for each of the geophysical techniques for both drumlins.