I. INTRODUCTION AND HISTORY OF THE DATABASE
The Nevada Test Site is situated within a 10,000 km2 province called the southwestern Nevada volcanic field (SWNVF) by Christiansen et al. (1977). The SWNVF contains multiple suites of Miocene silicic volcanic rocks, erupted from an evolving system of calderas (Figure 1). The volcanic rocks overlie a basement of Paleozoic sedimentary rocks. The general geologic framework and history of important work for this volcanic field are summarized by Byers et al. (1989). Collection of detailed geological information to support activities of the Nevada Test Site (NTS) began in the 1960's. Geoscientists from Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL), the U.S. Geological Survey (USGS), and various government contractors, particularly Raytheon Services Nevada (RSN), conducted numerous studies of the geologic framework to assist in the safe underground testing of nuclear devices. Development and appropriate integration of the geologic framework into testing activities resulted in successful geological containment of radionuclides from the underground tests. The surface expression of the underground testing can be seen in the photograph of Figure 2.
Figure 1. Calderas within the SWNVF (from Warren et al., 1989b), showing areal extents of large-volume ash-flow sheets. This representation is taken mostly from Byers et al. (1976b), with the addition of the Stonewall Mountain caldera complex described by Noble et al. (1984). More recent work by Carr et al. (1986), Noble et al. (1991), and Ferguson et al. (1994) have expanded, somewhat modified, or presented alternatives to this view. Values shown on the right and bottom margins of the figure represent UTM coordinates in kilometers.
Figure 2. Collapse features within Yucca Flat testing area of the Nevada Test Site, viewing to south. The vaporization of an enormous volume of rock during an underground nuclear explosion creates a void into which overlying rocks generally collapse. Ironically, collapses that reach the surface seal off any geologically available pathway for the release of radionuclides, and effectively guarantee underground containment of all radioactive gases produced by the nuclear explosion.
Geological data provided in this database were generated primarily by personnel of LANL and the USGS. Other organizations also retain datasets containing geological information obtained from samples collected within the SWNVF, both in hard copy and in electronic form.
Los Alamos National Laboratory has played a major role in testing activities. Geoscientists at LANL assembled various types of geological and geophysical data to support containment science for the safe underground testing of nuclear devices. Details of the evolution of geologic data and model development in support of the Containment program are provided in Appendix A. The geological data provided within the database were originally assembled beginning in 1987 within a non-relational database. General usage of these geological data in this form was difficult because of the reliance on proprietary software and operating systems, and the non-relational format of much of the data. Standardization of operating systems (to UNIX and WINDOWS), development of the Structured Query Language (SQL) standard for relational databases, and the availability of commercial SQL-compliant database implementations provided a strong incentive for the authors to restructure and reformat the geological data for input into a SQL-compliant database. The geophysical data formerly constituted the primary basis of the GEODES database (Winterkamp et al., 1985). With the addition of the geophysical data from GEODES to the original database (Warren et al., 2000), all these data now reside in a set of relational tables served by the Geographic Information System Laboratory (GISLab) facility in the Earth and Environmental Sciences Division at LANL. This revised database is maintained for public access through the internet at a site maintained by GISLab.