NEW GEOLOGIC SHADED RELIEF MAP OF VENEZUELA AT 1:750,000 SCALE

A new digital geologic map and GIS dataset represents the most up-to-date and comprehensive coverage of Venezuelan geology and topography available at a national scale. The product was created through vectorization of published paper 1:500,000-scale geologic maps, and diagrams illustrating the results of new 1:25,000-scale geological mapping. These data were integrated with an existing digital geological map covering the southern part of the country. Geologic polygon data were draped over a shaded relief image produced by processing of 90 m (3-arc second) radar interferometric data obtained by the shuttle radar topography mission (SRTM).

Geologic (units, faults, and folds) and hydrologic (rivers, streams, and lakes) data were digitized from a paper geologic map set for all of Venezuela north of the Orinoco River. Polygons representing geologic units were attributed by formation name in a GIS following the Léxico Estratigráfico de Venezuela, representing a significant improvement over the original paper map, where the unit polygons were identified only by age. Fold and fault type information also were included in the GIS, as were Quaternary right lateral strike-slip faults not previously incorporated at this scale. Significant revisions to the geology of the Cordillera de la Costa were incorporated by vectorization of new geologic mapping data. Geologic/hydrologic data for northern Venezuela were integrated with a digital geologic map of the Venezuela Guayana Shield to provide comprehensive coverage.

The shaded relief base represents a 10-fold increase in resolution over previously available elevation models. Values for null-data holes inherent in the SRTM elevation data set were filled by interpolation based on surrounding data cells using customized Arc Macro Language scripts. The digital elevation model data was hill-shaded using an illumination direction of 315 degrees at an angle of 65 degrees above the horizon to produce the shaded relief image.

A presentation quality image of the geologic shaded relief map of Venezuela in portable document format at 1:750,000-scale and individual GIS geologic/hydrologic data layers will be available online and on CD-ROM. Users of the digital map are encouraged to contact the authors to report inaccuracies that may be corrected in future versions.