Deep Crustal Structure; Rifting and Subsidence Theory
A large aperture seismic experiment (LASE) was conducted in the area of the Baltimore Canyon Trough (Fig. 1) by scientists and ships from the Lamont-Doherty Geological Observatory (L- DGO) of Columbia University, the Woods Hole Oceanographic Institution (WHOI), the University of Texas Institute for Geophysics (UTIG), and the Bedford Institute of Oceanography (BIO). Three ships, Oceanus, Moore, and Dawson, were used to acquire a body of exploration seismic data using a new and innovative method, synthetic aperture Common Depth Point (CDP) profiling, as well as the well established expanding spread profile method. This project was created to obtain information about velocities and structures of deep horizons that had been poorly resolved by previous surveys or by drilling.
The main scientific objectives were defined by questions arising from the analysis of USGS Line 25. These included determining the nature of material underlying Jurassic carbonates and the existence of an underlying basement ridge at the present shelf edge. It was also hoped that any structures associated with the east coast magnetic anomaly might be revealed. It was expected that the large offsets employed in the multi-ship CDP profiling method would allow improved velocity resolution and better rejection of multiple reverberation than in the case of conventional, single ship data.
Since this project involved innovative techniques of acquisition, processing, and analysis, it is necessary to describe them to some extent. The geological results are no less important, however, and provide important benchmarks for future interpretations of the development of the North Atlantic margin.
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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.