sim3129-readme.txt Irwin, W.P., 2010, Reconnaissance Geologic Map of the Hyampom 15' Quadrangle, Trinity County, California: U.S. Geological Survey Scientific Investigations Map 3129, scale 1:50,000 [http://pubs.usgs.gov/sim/3129/]. This geologic map and map database represent a digital rendition of Miscellaneous Field Studies Map MF-1809, by William P. Irwin (Irwin, 1985), with various improvements and additions. It was compiled digitally by Irwin and C.M. Wentworth from the MF map, supplemented by 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 Hyampom 15-minute quadrangle, together with structural data, fossil localities, and the locations of prospect pits. Geologic map units are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The compilation scale 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, 1972). 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. 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 are current as of 1951 (base map) or the early 1980s. 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. This geologic map has been compiled at a scale of 1:50,000, in order to be compatible with the earlier released geologic maps of the Weaverville and Hayfork 15' quadrangles (Irwin, 2009, 2010), but the reconnaissance nature of the work and the 1:62,500-scale of most of the source materials make the locational accuracy and detail only approximate. 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. Irwin, W.P., 1985, Reconnaissance geologic map of the Hyampom quadrangle, Trinity County, California: U.S. Geological Survey Miscellaneous Field Studies Map MF-1809, scale 1:62,500. Irwin, W.P., 2009, Geologic Map of the Weaverville 15' quadrangle, Trinity County, California: U.S. Geological Survey Scientific Investigations Map 3095, scale 1:50,000. Irwin, W.P., 2010, Reconnaissance geologic map of the Hayfork 15' quadrangle, Trinity County, California: U.S. Geological Survey Scientific Investigations Map 3119, scale 1:50,000. Irwin, W.P. and Blome, C.D., 2004, Fossil Localities of the Rattlesnake Creek, Western and Eastern Hayfork, and North Fork Terranes of the Klamath Mountains: U.S. Geological Survey Open-File Report 2004-1094. 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 - sim3129-readme.txt (Note - there is no text pamphlet accompanying this report.) 2. Version List - sim3129-version.txt: list showing status of any revisions to the report. 3. Map Graphics sim3129-map.pdf - geologic map and explanation in pdf format 4. GIS Layers - sim3129-arcpkg.zip: a package of exported ArcInfo coverages as follows sim3129-geol.e00 - ArcInfo Export file of the geologic layer, containing contacts, faults, and unit polygons. sim3129-atts.e00 - ArcInfo Export file of the attitudes layer, containing bedding, cleavage, foliation, and joint attitudes. sim3129-lins.e00 - ArcInfo Export file of the lineations layer, containing axes of minor folds. sim3129-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. sim3129-metadata.txt - text file of FGDC-compliant metadata documenting the GIS layers. 5. Base Image - sim3129-base.zip: Compressed directory containing an ArcInfo grid of the Hyampom, California 15-minute topographic map, in Albers NAD83 projection, together with a text description of the grid values for the different map components. 5a info directory 5b. sim3129base - ArcInfo grid of the Hyampom, California 15-minute topographic map, in Albers NAD83 projection. 5c. sim3129basenotes.txt - description of the base grid and meaning of its values