That rift zone split open and caused volcanic eruptions which created new oceanic crust -- what is today the crust of the Earth under the Atlantic Ocean. The rifting continues today at what's called the Mid-Atlantic Ridge.
"The age of the suture zone is believed to be about 250 million years old, but that's not very well constrained," said geologist Elias Parker, Jr., of the University of Georgia in Athens. He published a paper reviewing what's known about the Brunswick Magnetic Anomaly in the latest issue of GSA Today.
The big challenge in sorting out the history of the southeast U.S. is that there are intriguing magnetic signals, as well as gravimetric measurements, but there is not enough deep borehole studies or seismic data to confirm the faults and the proposed scenarios.
"There are deeper faults and more shallow features," said Parker. "It makes the interpretation really challenging."
Among the seismic projects that could help increase the resolution of the structures, said Parker, is the Southeastern Suture of the Appalachian Margin Experiment (SESAME) and the Suwanee Suture and Georgia Rift Basin Experiment.
"This is just the start to understanding the structure of the southeast U.S.," said Parker. "What I'm trying to do is come up with a simple explanation for this."