Eutaw, for which the Cretaceous marl formation is named, lies just off on the extended axis of the Appalachian Mountains where buried basins would be. Some researchers believe the Appalachians took a "downwarp" and is an enigma how or why congenital crust would do so. Some researchers using earthquake histories say they have tracked the orogeny all the way into Mexico as a syncline( downwarp).
There is a pre-Cambrian formation of granite and gniess( 1.3 billion ybp) which takes a deep down slope to the west from where it surfaces along the Alabama/Georgia border around Columbus/ Phenix City. It is hard to envision the interplay, as most geological research was directed at surface and mid depth oil and gas deposits. Only recently was it announced that a huge batholith of igneous rock under Pennsylvania accounts for the kink in the Appalachians there in the edge of New England.
While this doesn't say much about the origin of the Eutaw quake, it is food for thought. BTW many quakes at this depth are attributed to cavern collapse in limestone formations.
Eman
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