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北美和非洲大陆之间的裂谷作用和地壳变薄发生在三叠纪和早侏罗纪时,海底扩张则始于早至中侏罗纪。美国东部大陆边缘在侏罗纪的沉降极其迅速而多变,受到横向断裂带的控制,它把大陆边缘分成四个大沉积盆地—乔治滩盆地、巴尔的摩峡谷海槽、卡罗莱纳海槽和布莱克海台盆地。在乔治滩盆地钻遇上三叠世至下侏罗世蒸发岩沉积(包括岩盐),而在卡罗莱纳和巴尔的摩峡谷海槽的东海岸磁异常区已找到盐(?)底辟的线性链状构造。这些盆地中裂谷后未变形沉积单元的最大厚度分别为7、13、11和12公里。在这些盆地之下的三叠纪裂谷地堑中,变形的裂谷期沉积单元(在裂谷作用活跃期间沉积的沉积物)在有些地方超过5公里。穿过北部这三个盆地的重力模式表明在盆地下面下伏有8至15公里的过渡性地壳。过渡性地壳可能是由以前大陆地壳的引张和变薄所造成的。伏于350公里宽的布莱克海台盆地之下的较厚过渡性地壳(15至25公里)可能包含了混杂的大陆碎块和大量火山岩的混合。在大陆最初分离之后的10至15百万年中,扩张中心从布莱克海台西部之下突然向东移至布莱克陡崖,这可能就是造成该盆地异常宽阔的原因。
Rift and crustal thinning between North America and the African continent occurred during the Triassic and Early Jurassic, and seabed expansion began as early as the Middle Jurassic. The settlement of the eastern continental margin of the United States in the Jurassic was extremely rapid and variable. It was controlled by lateral fault zones and divided the continental margins into four major sedimentary basins - the Georgetown Basin, the Baltimore Gorge trough, the Carolina Sea trough and Blake Haitai basin. Triassic-Lower-Jurassic evaporite deposits (including rock salt) were drilled in the Georgetown Basin, while linear chains of salt (?) Diapirs were found in the magnetic anomaly areas of the East Coast of the Carolina and Baltimore Gorge troughs Like structure. The maximum thickness of undeformed sedimentary units in the middle rifts of these basins are 7, 13, 11 and 12 km, respectively. In the Triassic Rift Graben below these basins, deformed rift-period sedimentary units (sediments deposited during active rifting) exceeded 5 km in some places. Gravity patterns across all three of these northern basins indicate a transitional crust underlying 8 to 15 kilometers beneath the basin. The transitional crust may be caused by the extension and thinning of the previous continental crust. The thick transitional crust (15 to 25 km) beneath the Blake Basin, 350 km wide, may contain a mixture of mixed continental fragments and volcanic rocks. In the 10 to 15 million years that followed the initial secession of the continent, the sudden eastward expansion of the expansion center from beneath the Black Sea platform to the Black Cliffs was probably the reason for the exceptionally widening of the basin.