DISTINCT CRUSTAL STRUCTURE OF THE NORTH AMERICAN MID-CONTINENT RIFT FROM P WAVE RECEIVER FUNCTIONS
Outside of the MCR, the Moho is strong, sharp, and relatively flat, both beneath the Archean Superior Province and the Proterozoic terranes to its south. Inside the MCR, two weaker candidate Mohos are found at depths up to 25 km apart in the rift’s center. This intermediate layer between the candidate Mohos tapers towards the edges of the MCR. The presence of this transitional layer is remarkably consistent along the strike of the MCR, including beneath the jog in southern Minnesota, near the Belle Plaine Fault.
We interpret these results as evidence for extensive underplating as a defining characteristic of the rift and the rift remaining continuous throughout its jog in southern Minnesota, though with less reverse faulting than along the NNE striking parts of the rift.