The Mesozoic and Cenozoic rocks and sediments penetrated at Deep Sea Drilling Project sites in the North American basin show similar sequences of lithology, age, faunal assemblages, and petrographic composition, thus permitting recognition of six formations. These formations were mapped using a combination of reflection seismic data and drilling results.

Pelagic limestones dominate the Late Jurassic-Early Cretaceous; the oldest rocks are Oxfordian. These sediments were deposited in a deep bathyal environment above the carbonate compensation depth (CCD). The CCD shoaled abruptly in the Barremian; this shoaling was accompanied by development of euxinic conditions and formation of carbonaceous shales which continued through the Cenomanian. Starved-basin conditions and a shallow CCD resulted in deposition of pelagic multi-colored clays in the Late Cretaceous. The presence of Meastrichtian chalks above carbonate-poor Late Cretaceous clayey deposits indicates abrupt but temporary deepening of the CCD in the North American basin in the latest Cretaceous.

Deposition dominated by clayey sediments continued into the Paleocene on the Bermuda Rise, the only locality where this interval is represented. Siliceous deposits accumulated during early and middle Eocene time, probably below the CCD; the resultant cherty unit is a prominent seismic reflector (horizon A^c over much of the North American basin. The late Eocene and Oligocene are represented by clays, siliceous clays, and mass-flow deposits in the Bermuda Rise area. Along the continental margin, a major unconformity dated as late Eocene to Oligocene bevels Eocene to Lower Cretaceous rocks. Hemipelagic deposition of gray-green mud was dominant in the North American basin throughout the Neogene and continues to the present.

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