Late Quaternary Activity of the Cerro Goden Fault Zone, Transpressional Uplift of the La Cadena Range, and Their Possible Relation to the Opening of the Mona Rift, Western Puerto Rico
AU: * La\'{o}-D\'{a}vila, D A
EM: guatu@hotmail.com
AF: Florida International University, Department of Geology, Miami, FL 33199 United States
AU: Mann, P
EM: paulm@ig.utexas.edu
AF: Institute for Geophysics, University of Texas, Austin, TX 78713 United States
AU: Prentice, C S
EM: cprentice@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd MS 977, Menlo Park, CA 94025 United States
AU: Draper, G
EM: draper@servax.fiu.edu
AF: Florida International University, Department of Geology, Miami, FL 33199 United States
AB: The Cerro Goden fault zone coincides with an abrupt, linear mountain front separating the 270-361 m high La Cadena de San Francisco from the alluvium-floored A\~{n}asco valley. The offshore extension of the fault is described in other posters in this session. Previous workers have postulated that the Cerro Goden fault continues to the southeast of the A\~{n}asco Valley and merges with the Great Southern fault zone of south-central Puerto Rico. Using both 1:18,500 scale air photographs taken in 1936 and 1:40,000 scale photographs taken by the USDA in 1994, we identified geomorphic features suggestive of Quaternary fault movement including aligned and deflected drainages, apparently offset terrace risers, and mountain-facing scarps. All stream features suggest right-lateral offset. As with other large strike-slip faults, the active trace is about 500 m valleywards of a prominent mountain front. The active trace is in alignment with the linear bedrock fault mapped by McIntyre (1971) in the Central La Plata quadrangle sheet east of this area. Mapping of Paleogene bedrock units in the uplifted La Cadena range reveal narrow fault wedges of older basement rocks parallel to the range front and tighter folds and closely spaced faults within a 2 km wide zone along the southern edge of the range. Age constraints on left-lateral transpressional deformation of older rocks in the range front fault zone are poor given the absence of rocks younger than Eocene in the deformation zone. One possible explanation is an early, post-Eocene, pre-Quaternary phase of left-lateral shear as suggested by previous studies along the Great Southern fault zone to the southeast followed by a Quaternary phase of right-lateral shear. Such shear would be consistent with recent GPS results and the opening geometry of the Mona rift.
DE: 8000 STRUCTURAL GEOLOGY (New field, replaces single entry 8165)
DE: 8010 Fractures and faults
DE: 8100 TECTONOPHYSICS
SC: T
MN: Fall Meeting 2000