Idealized cross-section of the Central Valley.

Terrane, the Middleton Basin, was discovered north of Boston. These far-flung basins all have the same distinctive red-brown sediments, most also have the rust-colored traprock, and all are Mesozoic in age.

The similarity of all Mesozoic basins is uncanny and points to their common origin as great cracks associated with Pangaea's break-up. Geologists refer to valleys formed this way as "rift valleys" The splitting apart of Pangaea broke the Appalachians into a succession of flat-bottomed rift valleys and high mountain ranges. Many parallel cracks formed along the line of the Appalachian collision until separation finally concentrated on one line of rift valleys that eventually widened into the Atlantic Ocean. The presence of the Central Valley in southern New England indicates that for a while Atlas toyed with the idea of reopening the family business in the same place his father ran it between Proto-North America and Avalonia - before settling on the location further east - between Avalonia and Africa.

Although true at a basic level, the crack analogy oversimplifies the history of the Central Valley's Newark Terrane. A better picture is to conceive of the Valley's formation as a huge trapdoor, opening inward

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