New England and Gulf of Maine Gravity Map

Bouguer/Free air gravity anomaly map.  Click on map to view larger image (1.4 MB).

The top figure is the gravity map of the New England States and the Gulf of Maine, and is composed of simple Bouguer anomaly data on land and Free Air anomaly data in the ocean.  This combined Bouguer/Free Air gravity anomaly grid  was compiled using data from  35,644 gravity stations on land from ~70 sources and 27,251 shipborne measurements from 30 cruises.  In addition, these data were combined with 5,363 records from a separate file of Maine marine data (Dater and others, 1999) originally from a compilation by Bond (1993c).  There are a number of duplicate data points between the two offshore data sets.  The distribution of stations for all surveys is shown in the lower figure.  Most of the data points were derived from the NGDC gravity CD (Dater and others, 1999);  other stations are from Hittleman and others (1992).This grid is similar to that given in Phillips and others (1993), based on a 4-km grid by Godson and Scheibe (1982), except that the current grid has a 2-km interval and the data points are included. 

Observed gravity values on land are relative to the IGSN-71 datum, and were reduced to the Bouguer anomaly using the 1967 gravity formula and a reduction density of 2.67 g/cc.  The land and marine data were combined and converted to a 2-km grid using a minimum curvature algorithm. The combined anomaly grid  for the upper map and the individual stations may be downloaded. This project was supported by the Mineral Resources Program of the USGS.

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