7 Geophysics (Posters)

A QUANTITATIVE ANALYSIS OF PROPOSED MODELS OF THE SCRANTON GRAVITY HIGH

Paper number: 7-2
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

The Scranton Gravity High is an elliptically shaped gravity high of 40 mGals extending from Albany, NY 360 km to Harrisburg, PA. The anomaly has been considered the result of a dense mass of broad extent deep within or at the base of the crust. Three models were presented to account for this gravity high. The models are (1) basalt filled rift (2) intrusive from the asthenosphere and (3) upwarp of the mantle. Recent quantitative analyses of these models indicate that anomaly might be the result of density contrasts of shallower origin rather than the deep-seated buried models.

A computer analysis of these deep-seated models indicates they produce poor fits to the observed gravity data. A buried intrusive extending from the Moho at a depth of 35 km to near the surface requires an unreasonable density contrast. The upwarp of the mantle extending to 15 km depth also requires an unlikely density contrast. Several other models also produce poor fits to the observed gravity data. The best fit was obtained by a high density body with a density contrast of .10 gms/cc occurring at a shallow depth. This shallow origin for the anomaly seems the most likely explanation based upon the fit to the observed gravity.