Seafloor spreading magnetic anomalies in the Venezuelan Basin
Published:January 01, 1984
N. Ghosh, S. A. Hall, J. F. Casey, 1984. "Seafloor spreading magnetic anomalies in the Venezuelan Basin", The Caribbean-South American Plate Boundary and Regional Tectonics, William E. Bonini, Robert B. Hargraves, Reginald Shagam
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A compilation of existing magnetic data clearly demonstrates the presence of extensive, NE-SW trending, linear anomalies over the central Venezuelan Basin. These long wavelength, small amplitude anomalies are truncated in the east by a series of N-S linear anomalies over the Aves Ridge, and in the south by E-W trending anomalies over the Aruba Basin, Curacao Ridge, and Los Roques Basin. In the southeastern corner of the basin, there is a magnetic quiet zone similar to that observed in the North Atlantic and Pacific Oceans.
Analysis of the NE-SW anomalies reveals an axis of symmetry which crosses the basin from north of the Guajira Peninsula to near the Muertos Trough at 68° W. Modelling indicates that the linear anomalies are the result of a phase of seafloor spreading between 153 and 127 m.y. at a half rate of 0.4 to 0.5 cm y−1. The quiet zone is therefore believed to correspond to a period in the Middle Jurassic which may be characterized by frequent short reversals.
The magnetic study together with other geologic and geophysical evidence suggests that the Venezuelan Basin formed in the Pacific region as a western extension of the N. Atlantic in Middle-Late Jurassic. Spreading appears to have ceased when, in the early Cretaceous, the South Atlantic began to open. As a result of these changes in plate motion, the Venezuelan Basin became trapped behind the juvenile Antilles arc-trench system. The Venezuelan Basin was then gradually inserted into the Caribbean region as this system migrated eastward with respect to North and South America.