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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 110,
B06404,
doi:10.1029/2004JB003459,
2005
Vertical motions of the Puerto Rico Trench and Puerto Rico and their cause
Uri ten Brink
U.S. Geological Survey, Woods Hole, Massachusetts, USA
Abstract
The Puerto Rico trench exhibits great water depth, an extremely low gravity anomaly, and a tilted carbonate platform between
(reconstructed) elevations of +1300 m and −4000 m. I argue that these features are manifestations of large vertical movements
of a segment of the Puerto Rico trench, its forearc, and the island of Puerto Rico that took place 3.3 m.y. ago over a time
period as short as 14–40 kyr. I explain these vertical movements by a sudden increase in the slab's descent angle that caused
the trench to subside and the island to rise. The increased dip could have been caused by shearing or even by a complete tear
of the descending North American slab, although the exact nature of this deformation is unknown. The rapid (14–40 kyr) and
uniform tilt along a 250 km long section of the trench is compatible with scales of mantle flow and plate bending. The proposed
shear zone or tear is inferred from seismic, morphological, and gravity observations to start at the trench at 64.5°W and
trend southwestwardly toward eastern Puerto Rico. The tensile stresses necessary to deform or tear the slab could have been
generated by increased curvature of the trench following a counterclockwise rotation of the upper plate and by the subduction
of a large seamount.
Received 30
September
2004;
accepted 15
February
2005;
published 22
June
2005.
Keywords: dynamic topography;
slab tear;
Puerto Rico trench;
Caribbean plate;
Challenger Deep;
seamount subduction.
Index Terms: 8120 Tectonophysics: Dynamics of lithosphere and mantle: general (1213); 8122 Tectonophysics: Dynamics: gravity and tectonics; 8170 Tectonophysics: Subduction zone processes (1031, 3060, 3613, 8413); 3060 Marine Geology and Geophysics: Subduction zone processes (1031, 3613, 8170, 8413); 1219 Geodesy and Gravity: Gravity anomalies and Earth structure (0920, 7205, 7240).
Read Full Article (file size: 3365513 bytes) Cited by
Citation: ten Brink, U.
(2005),
Vertical motions of the Puerto Rico Trench and Puerto Rico and their cause,
J. Geophys. Res.,
110,
B06404,
doi:10.1029/2004JB003459.
This paper is not subject to U.S. copyright. Published in 2005 by the
American Geophysical Union.
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