A PRELIMINARY GRAVITY MAP OF PENNSYLVANIA

Over the last fifteen years, we have been collecting gravity data in Eastern Pennsylvania as part of numerous research and senior thesis projects. As these project have been undertaken, there was a need for data of a more regional nature in order to define regional trends so that residual anomalies could be more precisely defined. These data (National Geophysical Data Center and others) have been corrected for compatibility and integrated into our database. In the process we have compiled a gravity database for Pennsylvania with more than 13,000 observations.

There is a wide discrepency in the density of coverage throughout the state. While there is a high concentration of observations in southeastern Pennsylvania and along some of the major roadways (PA 15, 22 and 322), the western half of the state has a much lower density of coverage. The simple Bouguer gravity map shows some interesting long wavelength anomalies. Lavin (1999) has summarized the association of these anomalies with regional geologic features. For example, a gravity high (amplitude +50 mgals) extends SW from Wayne County to Juniata County (the Scranton and Newport gravity highs, which parallels the south side of the New York-Alabama lineament. Significant gravity lows (-30 to 40 mgals) are centered on Berks and Beaver counties.

The primary objective of this paper is to alert workers to our efforts to compile Pennsylvania gravity data from as many different sources as possible. This is intended to be a cooperative effort that will result in a detailed gravity map of Pennsylvania as well as a gravity database that will be accessible to all researchers, possibly through the Pennsylvania Geological Survey or national databases.