Gravity/Magnetic Maps 4 The structural complexity of the Precambrian terrain beneath The theory of seaHoor spreading has shown that recognizable, western New York indicates a complex history of geologic development linear magnetic anomalies are to be expected over oceanic crust. The abrupt termination of these linear sets of anomalies is usually The Bouguer gravity anomaly field in western New York is the most obvious indication of a fundamental change in the basement chiefly attributed to lithologic changes in the Precambrian basement since similar linear anomalies are very rare over continental beneath overlying Paleozoic sedimentary rocks. When the oceanic crust is deeply depressed by thick overlying use of the petrology of wells that have reached the Precambrian, in sedimentary sequences at passive margins. At subduction zones the linear Ontario area was produced. Gravity measurements were used as a anomalies are quenched because of greater source distance (as the primary means of extending lithologies of the Precambrian basement ocean crust is subducted) and, presumably.