Costa Rica Continental Margin: Line CR-7
Thomas H. Shipley, Richard T. Buffler, 1986. "Costa Rica Continental Margin: Line CR-7", Seismic Images of Modern Convergent Margin Tectonic Structure, Roland von Huene, Susan Vath, Christine Sperber, Bridgett Fulop, Lee Bailey, Monique Martin
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The seismic section across the Pacific margin of Central America off Costa Rica provides a structural cross section of the southern terminus of the Middle America trench. The section begins less than 10 km from the shoreline of the Nicoya Peninsula and extends for 70 km across the trench slope and trench, and into the ocean basin. Regionally, the trench shallows toward the southeast because of a large sea-floor rise, the Cocos Ridge, at the southern boundary of the Middle America trench. The Cocos and Caribbean plates are converging at about 9 cm/yr nearly normal to the margin (McNally and Minster, 1981), with earthquake activity defining a subduction zone dipping to the northeast (Burbach et al., 1984). Old oceanic crust is exposed on the Nicoya Peninsula in the form of Late Jurassic and Cretaceous volcanic and sedimentary rocks. The structural relationships within these rocks have been reported by a number of different investigators, but their exact origin remains unresolved (Dengo, 1962; Schmidt-Effing, 1979; Lundberg, 1982). The presently subducting ocean floor is of early Miocene age (Hey, 1977).
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In 1980, A. W. Bally assembled and edited an innovative three-volume “picture and work” atlas of seismic reflection record sections. This compilation of more than 130 excellent seismic section reproductions provided much new data from the earth's subsurface. For petroleum geologists, academic scientists, and students, it is the field geologist's counterpart of outcrops and type sections. The smaller collection of seismic sections presented in this Studies 26 publication was inspired by Bally's atlas, and follows his general format and philosophy. The objective is to provide a reference series of sections for the earth sciences and a vehicle for continuing scientific dialogue relating to modern convergent margins. This publication's assembled sections represent a single facet of that dialogue by bringing together a series of exceptional seismic sections from the fronts of presently active convergent margins around the Pacific.