60-28 Fracture Networks in the San Cristobal Canyon, Puerto Rico from High-Resolution Topography and GIS Analyses

Session: 2YC and 4YCU Geoscience Student Research Poster Showcase

Presenting Author:

Authors:

Abstract:

The San Cristobal Canyon is the deepest terrestrial canyon in Puerto Rico and one of the deepest in the Antilles.  It is currently a natural protected area and tourist attraction located between Barranquitas and Aibonito in East-Central Puerto Rico. Its geology consists primarily of tuffaceous sandstone, siltstone and tuffaceous conglomerates and flow breccias. One fault was mapped previously parallel to one segment of the canyon. Nevertheless, in other parts of the area, the Río Usabón, which flows through the canyon, meanders atypically, reaching ninety-degree bends at some points and step-like meanders at others. This would suggest that fractures have a larger role in the control of the river and on the formation of the canyon.

This study aims to use 1-m resolution digital elevation model to map the fracture networks in the San Cristobal Canyon area to gain insight into the formation of the canyon and the flow of the river.  In addition, we would like to answer the question of whether there is geomorphological evidence for active faulting in the area. We used QGIS software to analyze the topographic and geomorphologic features of the canyon. We created elevation profiles and a geomorphic indicator ranking system to answer the question. In addition, we solved for three-point problems to calculate strike and dip of the layers. These methods were used in conjunction with one another to evaluate the likelihood of an active fault presence.

The results reveal geomorphologic elements, such as scarping and drainage patterns, that suggest that there is likely a fracture set striking NW-SE that coincides with bends in the river. However, no strong evidence of active faulting has been found suggesting that the canyon formed by uplift and downward erosion of the rock by the river that followed old fractures. Research is ongoing to conclude with greater certainty the presence of active faulting within the canyon.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8184

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.