CASTILE EVAPORITE KARST POTENTIAL MAP OF THEGYPSUM PLAIN, EDDY COUNTY, NEW MEXICO ANDCULBERSON COUNTY, TEXAS: A GISMETHODOLOGICAL COMPARISON

摘要

Castile Formation gypsum crops out over —1,800 km~2 in the western Delaware Basin where it forms the majority of the Gypsum Plain. Karst development is well recognized in the Gypsum Plain (i.e., filled and open sinkholes with associated caves); however, the spatial occurrence has been poorly known. In order to evaluate the extent and distribution of karst development within the Castile portion of the Gypsum Plain, combined field and Geographic Information System (GIS) studies were conducted, which enable a first approximation of regional speleogenesis and delineate karst-related natural resources for management. Field studies included physical mapping of 50, 1-km2 sites, including identification of karst features (sinkholes, caves, and springs) and geomorphic mapping. GIS-based studies involved analyses of karst features based on public data, including Digital Elevation Model (DEM), Digital Raster Graphic, (DRG) and Digital Orthophoto Quad (DOQ) formats. GIS analyses consistently underestimate the actual extent and density of karst development, based on karst features identified during field studies. However, DOQ analyses coupled with field studies appears to produce accurate models of karst development. As a result, a karst potential map of the Castile outcrop region was developed which reveals that karst development within the Castile Formation is highly clustered. Approximately 40% of the region effectively exhibits no karst development (<1 feature/km~2). Two small regions (<3 km~2each) display intense karst development (>40 features/km~2) located within the northern extent of the Gypsum Plain, while many regions of significant karst development (>15 features/ km~2) are distributed more widely. The clustered distribution of karst development suggests that speleogenesis within the Castile Formation is dominated by hypogenic, transverse processes.