32-10 Gravitational Survey to Further Characterize a Paired Gravity Anomaly within the Benton Uplift of the Ouachita Mountains near Hot Springs, Arkansas

Session: Latest Research Advances in Structural Geology and Tectonics (Posters)

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Abstract:

The Ouachita mountains formed as a result of a collision between North American continental crust and an unexposed arc terrane during the Pennsylvanian to early Permian Period. These rocks are heavily faulted and folded. The Benton Uplift contains some of the oldest exposed formations in the Ouachita mountains, including deep clastic and marine sediments like the Arkansas Novaculite. West of Hot Springs, Arkansas, the Benton Uplift is underlain by a paired gravity anomaly with an amplitude of ~80 mGal. Nicholas & Rozendal (1975) theorized that the gravity low may be caused by a “downwarp of the crust into the mantle” (Lyons 1961), however the cause of the adjacent gravity high is still debated.

This paired anomaly appears to be correlative along the broader Ouachita orogenic belt for ~800 km to the southeast, extending toward the Marathon uplift in West Texas. Previous research has attributed the gravity high to a combination of basement uplifts and mafic intrusions associated with aborted Precambrian rifting along the belt (Kruger & Keller 1986).

To further characterize the Benton Uplift, we acquired gravity data along a north-south transect ~30 km east of two earlier north-south profiles (Kruger & Keller 1986, Mickus & Keller 1992). We performed simultaneous forward modeling of our gravity data in conjunction with previously acquired airborne magnetic data to interpret a geologic cross-section along the transect (Bankey & Daniels 2008).

The upper crustal structure in our model closely matches that of Mickus & Keller (1992), although we found no evidence of the mafic intrusion reported beneath the Ouachita accretionary wedge. This absence may be due to the more southern extent of our survey. Additional seismic and magnetic surveys farther south and along the length of the Ouachita orogenic belt are needed to further test the hypothesis that a combination of basement uplifts and dense, deep-crustal mafic intrusions are the most likely sources for the paired gravity anomalies.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8156

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