R.H. Lippert, 1983. "The “Great Stone Dome”—A Compaction Structure", Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces, A. W. Bally
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Seventy miles east of the New Jersey coast, in the approximate center of the offshore Baltimore Canyon Basin, is a buried Early Cretaceous basic igneous stock. Compaction of Jurassic and Cretaceous sediments around the stock created a nearly symmetrical dome. This feature has been labeled the "Great Stone Dome."
Jurassic and Early Cretaceous strata, landward of the present-day shelf-slope break, are composed primarily of shallow water marine sandstones and shales. This section was intruded by the stock approximately 108 m.y. ago. While the stock is not clearly visible on seismic profiles, the structural effects of the intrusion are quite clear. The igneous mass is at a present day depth of 7,600 ft (2,316 m), is 3 to 5 mi (4.8 to 8 km) in diameter and is roughly circular in outline. Uplift and disruption of the strata by the emplacement of the stock is evident on seismic data as far as 10 mi (16 km) away. Seismic data also indicate that 5,000 to 6,000 ft (1,524 to 1,829 m) of sedimentary section was displaced vertically above the center of the stock.
Reconstruction of the late Aptian or early Albian landscape provides a dramatic picture. The domelike uplift created by t'e stock was a mountainous feature, approximately 1 mi (1.6 km) high and 18 mi (29 km) wide, on a broad, low-relief coastal plain. Erosive destruction of this topography occurred over an approximate 10 m.y. period of time. At the end of this period, the topography had been leveled. By the end of Albian time, 2,200 ft (671 m) of marine sandstone were deposited above the erosional surface and stock. As burial continued, the clastic section around the stock compacted beneath an increasing sediment load. The igneous core behaved as an incompressible buttress, and differential compaction created a nearly symmetrical dome in the units overlying the stock.
Present day depth of burial to the top of the unconformity on the intrusive is 7,600 ft (2,317 m). An Albian seismic reflector 1,600 ft (488 m) above this unconformity displays 1,300 ft (396 m) of structural relief between a point overlying the stock and a point overlying undisturbed sediments 10 mi (16.1 km) away.
Even with basinal tilt compensating for 500 ft (154 m) of compaction on the northwest flank of the dome, simple closure on the Aptian seismic event covers 100,000 acres and reaches a maximum of 900 ft (274 m) at the midpoint of the structure. The intrusion and overlying sedimentary drape make up the most prominent structural feature on the Mid-Atlantic continental shelf.
On August 17, 1976, the first Federal Lease Sale in the Atlantic was held. The oil industry paid $650 million for 37 tracts on the crest and flanks of the structure. Subsequently, seven wildcat failures have been drilled. The leases have now been surrendered or expired. The "Great Stone Dome," the largest and most promising structure in Baltimore Canyon Basin, is dry.
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Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces
Until a few decades ago, structural and regional geology were traditionally the preserve of field geologists. They usually mapped areas of outcropping deformed rocks and supplemented their work by laboratory studies of rock deformation and by theoretical work. Structural geology became tied to the geology of uplifts, folded belts, and underground mines, all of which were accessible to direct observation. Since World War II we have witnessed a tremendous development of geophysics in oceanography and in petroleum geology. Academic geophysicists in oceanography led their geological colleagues into modern plate tectonics and industry geophysicists developed reflection seismology into a superb structural mapping tool that penetrated the subsurface.
Today we are facing a situation where instruction and textbooks in structural geology are almost entirely dedicated to rock deformation, analytical techniques in detailed field geology and summaries of plate tectonics. Illustrations based on reflection seismic profiles are virtually absent in textbooks of structural geology. These texts illustrate only the parts of the proverbial elephant, together with some conjecture, but without ever offering a glimpse of the whole elephant.
Some of the reason cited for the relative scarcity of published reflection profiles are: 1) the confidentiality of exploration data; 2) difficulties in the photographic reduction and reproduction of seismic profiles for a book format; 3) the two-dimensional nature of vertical reflection profiles; and 4) the obvious distortions in reflection profiles that are typically recorded in time.
The AAPG leadership felt that it was time to attempt to correct the situation and to produce this picture and work atlas. The first volumes, of what may become a series of volumes, are addressing an audience that includes: petroleum geologists concerned with structural interpretations; exploration companies that provide in-house training; the AAPG continuing education program; and academic colleagues interested in updating their curricula in structural geology by inclusion of reflection profiles from the “real world” in their teaching.
The atlas is not meant to be a textbook in reflection seismology (instead we listed some at the end of this introduction) nor a text in structural and/or regional geology. Our intent is simply to provide a teaching tool.