Abstract

Last Chance Canyon is located in southeastern New Mexico, in the Guadalupe Mountains 20-km northwest of the Capitan Escarpment. The Grayburg Formation (Middle Permian, Guadalupian) is well exposed on the canyon walls throughout the area. The purpose of this research is to build a three dimensional (3-D) framework model of the lower Grayburg Formation in order to better understand the stratal geometries associated with the onlap of the Grayburg composite sequence onto the underlying San Andres composite sequence. Such knowledge is useful in characterization of the subsurface hydrocarbon reservoirs in the Grayburg Formation. Using laser imaging detection and ranging (LIDAR), Differential Global Positioning Systems (DGPS), and Geographical Information Systems (GIS) technologies, we generated high-resolution, digital 3-D topographic and stratigraphic surface models of the lower Grayburg Formation in the mouth of Last Chance Canyon and into the entrance of Gilson Canyon. Since the spring of 2009 more than 30 LIDAR scans have been performed in order to cover an area of approximately 1.3 square miles. The high-resolution LIDAR scans sampled the canyon outcrop at a 5- to 20-cm spacing yielding over 1 million topographic measurements. In addition to the LIDAR scans, stop-and-go kinematic DGPS surveys have been used to map out the Hayes Sandstone marker bed. The Hayes Sandstone is a well-exposed marker bed within the lower Grayburg Formation that can be easily identified in outcrop and in aerial photographs. It provides a reliable datum from which to map underlying units that display subtle but significant changes in geometry and facies. We integrated all LIDAR scans, DGPS data, field photographs, and previously obtained aerial photographs to build digital elevation models (DEM’s) and stratigraphic surface models of the study area. Using these models, we performed detailed characterization of the structural orientation and thickness variation of the Hayes Sandstone and adjacent beds.