Cretaceous and Cenozoic tectonism on the Atlantic coastal margin
Regional tectonism on the Atlantic coastal margin is expressed in a variety of ways such as uplift, subsidence, tilting of the landmass, geomorphic features, seismicity, and faulting. Of these features, faulting probably is the most definitive evidence of crustal deformation. Major episodes of faulting such as the ductile shearing associated with dynamic metamorphism in the exposed Appalachians and rift faulting associated with the formation of early Mesozoic basins along the Atlantic seaboard have long been a part of the geologic knowledge. However, faulting related to more subtle events, such as the uplift of the Blue Ridge Mountains or post-rift downwarp of the Atlantic continental margin, has received far less attention even though it is an important element of modern geology. Prior to 1970, the eastern United States was generally considered devoid of faults of post-Jurassic age even though evidence of such faulting was available in the late 1800's. McGee (1888) and Darton (1891) recognized faults in Virginia, Maryland, and Washington, D.C. that involved the juxtaposition of crystalline “basement” and Cretaceous or younger Coastal Plain strata. These observations and the local linearity of the inner margin of the Coastal Plain (Fall Line) lead them to postulate a tectonic control for the updip limit of sedimentation. Confirmation of widespread post-Jurassic tectonism, however, was not readily available and arguments favoring passive warping of the continental edge dominated geologic thought.
In the 1970's, the construction of nuclear power plants, large dams, and other large structures generated a need to understand Cenozoic tectonism and seismicity in eastern North America. The resulting studies of fault activity in the eastern United States provided evidence of many large, previously unrecognized, Cretaceous and Cenozoic fault zones. For example, Jacobeen (1972), Mixon and Newell (1977), Prowell and O’Connor (1978), Dis- chinger (1979), Reinhardt and others (1984), and Dischinger (in press) have described faults with vertical displacements of 30 to 76 m and mapped lengths as great as 100 km (Fig. 1).
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The Atlantic Continental Margin
This synthesis covers stratigraphy, depositional processes, and geophysical interpretation of the major onshore and offshore marginal basins from Maine to the Bahamas, and includes an up-to-date review of thinking on regional tectonic history. Additional chapters discuss the theoretical aspects of thermal evolution, subsidence, and seismic stratigraphy as applied to this region. Geological resources including petroleum, water, sand and gravel, hard minerals, and heat flow are reviewed, and environmental hazards such as seismicity, coastal erosion, waste disposal and submarine instability as it relates to site of drilling platforms and mining are evaluated. A summary chapter reviews areas of controversy and suggests key topics for research.