2 Data & Data corrections
The Bouguer gravity anomaly data was downloaded for the Covington pluton region from the National Center for Environmental Information (NOAA) (fig. 2). The Bouguer gravity map of the New Madrid region was composed of several data sets that incorporate more than 14,800 gravity stations. The average station spacing is around 2 km with several gaps along the Mississippi River and over wildlife refuges and lakes \cite{langenheim1995,abebooks}. The data have been corrected to free-air gravity values using standard formulas. Bouguer and terrain corrections were fitted to the free-air value at each station to determine the full Bouguer gravity anomalies using a standard reduction density of 2.67 g/cm3\cite{abebooks}. The data have been edited to remove single-station anomalies and then gridded using a 1-km interval. All observed gravity values were referenced to the IGSN71 datum as specified by and were then reduced to create Bouguer anomaly values using standard formulas. The accuracy of the measurements is around 0.2 mGal \cite{langenheim1995,abebooks}.