CORRELATION OF GEOLOGY WITH THE PRELIMINARY GRAVITY MAP OF PENNSYLVANIA

As part of a project to create a gravity map of Pennsylvania, we have been compiling gravity data from various sources including the National Geophysical Data Center, and other academic sources. In addition, we have collected new gravity data in eastern Pennsylvania as part if various research and thesis projects. These data have been corrected for compatibility and integrated into one large database. At the present time our gravity database for Pennsylvania has more than 13,000 observations.

Unfortunately, there is a wide discrepancy 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 the western half of the state has a much lower density of coverage. The long wavelength anomalies on the simple Bouguer gravity map have been correlated with regional geologic features Lavin (1999). For example, a gravity high (+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 increased density of gravity observations that we have collected in southeastern Pennsylvania allows for much more detailed analysis and modeling of subsurface geologic features. Specifically, we have modeled the structure of the sills in the Newark Basin as well as the border fault on the northern margin of the Basin.

Since a greater density of observations will be need in order to conduct detailed interpretation in other parts of Pennsylvania, we will continue to compile Pennsylvania gravity data from as many different sources as possible, including collecting new data. 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.