Irwin, W.P., 2009, Geologic Map of the Weaverville 15' Quadrangle, Trinity County, California: U.S. Geological Survey Scientific Investigations Map SIM-3095, map scale 1:50,000. This geologic map and map database represents a digital rendition of Miscellaneous Field Studies Map MF-275, 1963, by William P. Irwin, with various improvements and additions. It was compiled digitally by Irwin and C.M. Wentworth from original compilations, field notes and field sheets in the possession of W.P. Irwin. The map shows the general distribution of bedrock and surficial deposits of the Weaverville 15-minute quadrangle, together with structural data and the location of prospect pits and mine adits. Geologic map units are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:50,000 or smaller. The geology depicted on this map was part of the basis on which Irwin introduced the concept of geologic terranes (Irwin, W.P., 1972, Terranes of the western Paleozoic and Triassic belt in the southern Klamath Mountains, California, in Geological Survey research 1972: U.S. Geological Survey Professional Paper 800-C, p. C103-C111). This database and accompanying plot files depict the distribution of geologic materials and structures at a regional (1:50,000) scale. The report is intended to show the geologic framework and geologic history of the region, and to aid in the search for new deposits of minerals, particularly gold and copper. The original MF publication is black and white, including the base, and is extremely difficult to read. It should be noted that cultural information in the base map and the locations of prospects and adits are current as of 1950 (base map) or the early 1960s. The 15-minute topographic series has long been abandoned by the U.S. Geological Survey, but was the best regional scale for the map at the time it was originally prepared. The base image included herein was prepared from a color raster scan of an old edition sheet of the topographic map. Because the author compilations were originally prepared at 1:50,000 for later reduction to MF publication scale of 1:62,500, it was possible here to compile at 1:50,000. NOTE that the projection datum for both the Arc Export GIS layers (Albers projection) and the Arc shape files (decimal degrees) is NAD83. The map graphic, in contrast, was assembled in a Polyconic projection with datum of NAD27. Projection ALBERS Datum NAD83 Units METERS Spheroid GRS1980 Parameters: 1st standard parallel 34 0 0.000 2nd standard parallel 40 30 0.000 central meridian -120 0 0.00 latitude of projection's origin 0 0 0.000 false easting (meters) 0.00000 false northing (meters) -4000000.0000 The report consists of the following parts: 1. This README - sim3095-readme.txt (Note - there is no text pamphlet accompanying this report.) 2. Version List - sim3095-version.txt: list showing status of any revisions to this report. 3. Metadata file - sim3095-metadata: text file of FGDC-compliant metadata documenting the GIS layers. 4. Map Graphics sim3095-map.pdf - geologic map and explanation in pdf format 5. GIS Layers - as packages of exported ArcInfo coverages and of shape files 5a. sim3095-arcpkg.zip - package of coverages as Arc export files sim3095-geol.e00 - ArcInfo Export file of the geologic layer, containing contacts, faults, and unit polygons. sim3095-atts.e00 - ArcInfo Export file of the attitudes layer, containing bedding, cleavage, foliation, joint, shear, and aplite dike attitudes. sim3095-lins.e00 - ArcInfo Export file of the lineations layer, containing axes of minor folds and dips of contacts and faults. sim3095-pts.e00 - ArcInfo Export file of the points layer, containing locations of limestone (ls) and marble (m) bodies too small to show at map scale, together with mines and prospects and the location and orientation of mine adits. sim3095-fosl.e00 - ArcInfo Export file of the fossil localities layer, including locality numbers keyed to this map graphic and to Irwin and Blome, 2004, and the original field sample numbers. See map explanation for ages. sim3095-metadata - text file of FGDC-compliant metadata documenting the GIS layers. 5b. sim3095-shapepkg.zip - package of Arc shape files sim3095ln.shp - Arc shape file containing contacts, faults, and other boundaries sim3095py.shp - Arc shape file containing unit polygons sim3095at.shp - Arc shape file containing attitudes: bedding, cleavage, foliation, joints, shears, and aplite dikes sim3095li.shp - Arc shape file containing lineations: axes of minor folds and dips of contacts and faults sim3095pt.shp - Arc shape file containing locations of limestone (ls) and marble (m) bodies too small to show at map scale, together with mines and prospects and the location and orientation of mine adits. sim3095fs.shp - Arc shape file containing fossil localities layer, including locality numbers keyed to this map graphic and to Irwin and Blome, 2004, and the original field sample numbers. See map explanation for ages. 6. sim3095-base.zip - compressed Directory containing Base Image and associated files 6a. sim3095-base - ArcInfo grid of the Weaverville, California 15-minute topographic map, in Albers NAD83 projection. 6b. info - Info directory associated with an ArcInfo grid 6c. sim3095basenotes.txt - description of the base grid and meaning of its values