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