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Variation in structure, style, and driving mechanism of adjoining segments of the North Panama deformed belt

By
Eli A. Silver
Eli A. Silver
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Joseph Galewsky
Joseph Galewsky
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Kirk D. McIntosh
Kirk D. McIntosh
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Published:
January 01, 1995

The western part of the North Panama deformed belt (NPDB) undergoes a number of changes in the orientation of the frontal thrusts, in marked contrast to the eastern part of the NPDB, which shows very little change over distances of 150 km. In the western part of the belt, vergence and structural style of the frontal thrusts vary rapidly along the belt, again in contrast to the eastern part of the belt. The northeast-trending part of the western NPDB appears to be constrained in orientation by the slope of the Panama arc, which lies parallel to the thrust front. Farther west the belt trends northwest, and the thrust front migrates across the slope to the shelf area, where it has been identified by studies of the April 22, 1991, earthquake. Seismic data offshore from the surface location of this earthquake show no signs of crustal deformation, further constraining the location of the thrust front. The northwest orientation of the thrust belt on- and offshore of Costa Rica is consistent with a kinematic mechanism related to collision of Costa Rica by the Cocos Ridge. A proposal to explain the fact that the thrust front is located on the shelf, rather than at the base of the slope in its westernmost position, is impedance of thrusting as a result of the heavy load of sediment deposited by the Costa Rica fan. Thus several kinematic mechanisms are operating around the NPDB, producing very different directions of thrust belt orientation. In addition, several more mechanisms, such as slope stress, sediment loading, and possibly the structure of the lower plate, are operating to modify the orientation of the frontal thrusts.

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Contents

GSA Special Papers

Geologic and Tectonic Development of the Caribbean Plate Boundary in Southern Central America

Paul Mann
Paul Mann
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Geological Society of America
Volume
295
ISBN print:
9780813722955
Publication date:
January 01, 1995

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