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Abstract

Summaries of simple Bouguer gravity surveys in Georgia and their interpretations by the School of Geophysical Sciences, Georgia Institute of Technology, are presented. These surveys, primarily at a spacing of about 1 km, cover parts of the folded Appalachians, the Inner Piedmont, the Charlotte and Carolina Slate belts, and the Coastal Plain. In the folded Appalachians, positive anomalies of up to 5 mGal occur over outcrops of the carbonate members of the sedimentary sequence, indicating that these members are denser than the rest of the sequence. Few Bouguer anomalies are found over the fault contact between the folded Appalachians and the Blue Ridge, and these seem to correlate with topography. There is a general lack of anomalies owing to near-surface sources in the Inner Piedmont, although a large regional anomaly there is caused by lower crustal sources. In contrast, large Bouguer anomalies of 20-mGal amplitude are associated with surface exposures of mafic rocks (positive anomalies) and granites (negative anomalies) in the Charlotte and Carolina Slate belts adjacent to the Inner Piedmont. The fault contact between the Inner Piedmont to the northwest and the Charlotte or Carolina Slate belt to the southeast is the site of a steep gradient in the Bouguer gravity, owing to denser, more mafic rocks in the upper 5 km of the crust on the southeast side. In the Coastal Plain, many Bouguer gravity anomalies and total-magnetic-field anomalies are caused by Triassic rift structures. Another feature of the Bouguer gravity field in the Coastal Plain is a correlation of gravity and topography, suggesting that basement structures control topography in some regions.

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