Abstract

Two thousand and ninety-eight gravitational and magnetic stations were established to study the regional extent and distribution of large-scale anomaly variations and also the effect of local geologic structural and lithologic variations on the observed anomalies. About half the stations were distributed with an average station spacing of 4 miles on profiles across an area extending from the northern tip of New Jersey to Cape Cod, Massachusetts, and southward to Cape Henlopen, Delaware, Washington, D. C., and Harrisburg, Pennsylvania. The balance of the stations were concentrated in a strip 4 miles wide extending from Barnegat Bay to Phillipsburg, New Jersey, with a station spacing of .3 mile on traverses about a mile apart.

The survey shows several previously unknown anomaly areas as well as the extent of those from known earlier investigations, and the trend of all these anomalous areas parallels the structural trends of the Appalachian Mountain system. On the more detailed survey marked local anomalies are superimposed upon the large regional features. These local variations reach their greatest magnitude in the area of exposed pre-Cambrian and Lower Paleozoic rocks, and these same lithologic types appear to control the, local anomalies in both the Triassic and Coastal Plain areas except where there is intrusive diabase. Depth of sediments, structural displacement, and basement surface configuration apparently exert only a minor control in these areas on the anomalies as compared to the basement lithology. Similarly, the large regional anomalies appear to be related to intra-basement lithologic variations.

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