Mark B. Gordon, William R. Muehlberger
The Guayape fault extends from the Caribbean coast southwest to the Pacific coast at the Gulf of Fonseca. The Valle de Catacamas is a major physiographic basin centrally located along the west side of the Guayape fault. Increasingly deeper structural levels are encountered from west to east in the footwall block of the north range-bounding normal fault. At the west end of the valley Tertiary(?) mafic volcanics crop out in the footwall block. To the east the mafic volcanics are underlain by the Upper Cretaceous Valle de Angeles molasse. About 10 km farther east, the relief north of the frontal fault is much greater and quartz pebble sandstone (Honduras Group?) is overlain by limestone. The limestone is penetratively cleaved near the frontal fault with the cleavage essentia ly parallel to the fault. Thus, the normal faulting may be following the trend of a major preexisting weakness defined by the cleavage.
At the northeast end of the valley, the sedimentary rocks are underlain by metamorphic basement. Thus, the greater topographic relief and deeper structural levels in the footwall near the Guayape fault indicate that the normal faults have a greater displacement near the Guayape fault and this displacement decreases to the west away from the fault. Evidence for normal faulting along this range front includes mesoscale structures on fault planes and large-scale faults which place younger rocks on older rocks.
Preliminary analysis of fault slip data (slickenslide planes and striae) suggests that ^sgr3 is approximately 310°, consistent with formation of the valley by right-lateral shear along the Guayape fault.
Fresh fault scarps, normal faulting on the north side, and the lower topographic relief on the south side suggest that the Valle de Catacamas is a young, asymmetric fault wedge basin formed by dextral shear along the Guayape fault.
AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.