Insights into the Southern Oklahoma Aulacogen Using Gravity Model Comparisons of the Reelfoot Rift

The Southern Oklahoma Aulacogen and Reelfoot Rift are Precambrian continental rifts within North America that formed during the same continental breakup ≈560 Ma. These rifts likely underwent similar rifting processes and post-rift subsidence. Today the Reelfoot Rift has been slightly inverted and has a Bouguer gravity low, whereas the Southern Oklahoma Aulacogen has been inverted by 11 km and has a Bouguer gravity high. This study uses gravity modeling to constrain subsurface rift structures to compare the development of these rifts and determine why their gravity profiles are so different. Initially I investigate the gravity effects of sediment-filled rift basins, rift pillows, rift inversion, and lithology. Results confirm that sedimentary basins produce negative gravity anomalies, rift pillows produce positive gravity anomalies, the thickness of each increases the effect, and rift pillow proximity to the surface as controlled by inversions increases the gravity anomaly. I demonstrate that a 5-10 km thick rift pillow could fit the observed gravity anomaly of the Southern Oklahoma Aulacogen. Finally, this study compares the gravity profiles from a 10.5-km uplifted Reelfoot Rift to the current Southern Oklahoma Aulacogen and between a 10.5-km subsided Southern Oklahoma Aulacogen to the current Reelfoot Rift to better understand how these rifts evolved and to further constrain the differences and similarities between these rifts.