Abstract

Detailed geologic maps are critical for activities related to energy, minerals, groundwater, hazards, infrastructure, and earth science research as well as teaching. The Bureau of Economic Geology, as the State Geological Survey of Texas, has produced geologic maps for over 100 years. With more than 90% of the state unmapped at 1:24,000 scale, there is opportunity to produce original or compile analog geologic maps using an integrated digital and traditional mapping approach. Geologic mapping has evolved over the last 30 years due to Global Positioning Systems (GPS), Geographic Information Systems (GIS), digital elevation data (lidar), and smart phones. Modern geologic maps are geospatial databases that contain standardized and detailed attributes and metadata for line, point, and polygon features. These features can be stored, shared, symbolized, queried, analyzed, and presented in GIS.

A recent approach to geologic mapping of the Grit Quadrangle (Mason County) illustrates the integration of standard geologic field methods with evolving technologies and data, and the new GIS geologic map database schema (GeMS) prescribed by the U.S. Geological Survey. A preliminary geologic map of this quadrangle was created in GIS using existing maps, orthophotos, and especially the digital elevation models derived from lidar, which can be used to create shaded relief bare-earth models. Field work was iterative with GIS and helped verify the map, identify problem areas, and test hypotheses. Digital field data were collected with a smart phone mapping application and traditional field tools such as Brunton compass, hammer, hand lens, and field notebook. The GIS map database follows the GeMS schema, and an Open-File Map (PDF) was constructed with standard graphics software. The resulting geologic map and accompanying geospatial database will support continued research on earth resources. The approach serves as an evolving model for future geologic mapping.