Baltimore Canyon Trough's Great Stone dome is one of the largest, most prominent subsurface structural features in the Atlantic offshore. The dome, with nearly 140,000 ac under closure and more than 11,000 ft of structural relief, was formed by the early Late Cretaceous intrusion of a large mafic igneous body. The uplifting resulted in a major Barremian unconformity across the dome along with minor higher unconformities.

The dome was the site of intense bidding during 1976 when $651 million was bid for 37 tracts including $107.8 million for one crestal tract. Seven wells were subsequently drilled on the dome to total depths from 12,000 to 17,449 ft. The wells penetrated Cretaceous and Jurassic sandstones with porosities ranging up to 30%, but none encountered pay or significant shows. Lack of hydrocarbons in the section tested appears to be a result of low organic matter content of shales. Thermal maturation profiles show source rocks changing abruptly from immature to overmature across the Barremian unconformity. If hydrocarbons were generated (probably gas), lack of adequate seals at or above the unconformity prevented entrapment in crestal parts of the structure.

The seven wells mainly tested structural traps on the dome. Additional prospects remain to be tested, such as possible flank fault traps and stratigraphic traps formed by sands pinching out around the dome's flanks where mature source rocks are likely to occur.

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