Volume 32 Issue 6
Article, p. 4-11 | Full
Three Major Failed Rifts in Central North America: Similarities and Differences
The North American craton preserves nearly two billion years of geologic history, including three
major rifts that failed rather than evolving to continental breakup and seafloor spreading. The
Midcontinent Rift (MCR) and Southern Oklahoma Aulacogen (SOA) show prominent gravity anomalies
due to large volumes of igneous rift-filling rock. The Reelfoot Rift (RR), though obscure in
gravity data, is of interest due to its seismicity. The ca. 1.1 Ga MCR records aspects of the
assembly of Rodinia, whereas the ca. 560 Ma SOA and RR initiated during the later breakup of
Rodinia and were inverted during the assembly of Pangea. Comparative study of these rifts using
geophysical and geological data shows intriguing similarities and differences. The rifts formed
in similar tectonic settings and followed similar evolutionary paths of extension, magmatism,
subsidence, and inversion by later compression, leading to similar width and architecture.
Differences between the rifts reflect the extent to which these processes occurred. Further
study of failed rifts would give additional insight into the final stages of continental rifting
and early stages of seafloor spreading.
Manuscript received 8 June 2021. Revised manuscript received 11 Nov. 2021.
Manuscript accepted 19 Feb. 2022. Posted 30 Mar. 2022.
© The Geological Society of America, 2022. CC-BY-NC.
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