Reconnaissance Geologic Map of the Dixonville 7.5' Quadrangle, Oregon, USGS OFR 01-226

This study was undertaken as part of a contribution to 1:100,000 mapping of
the Roseburg 30' x 60' quadrangle (Wells, et al., 2000). The purpose of this
mapping was to assess the oil and gas potential of the Tertiary Tyee basin (see
Ryu, et al., 1996). This database and accompanying plot file depict the
distribution of geologic materials and structures at a large (1:24,000) scale.
The report is intended to provide geologic information for the study of
material properties, mineral resources, and geologic hazards. In addition, the
report contains new information and interpretations about the regional geologic
history and framework. However, the scale of this report does not provide
sufficient detail for site development purposes. For example, landslides in the
database are generalized and many smaller slope failures are not shown.

This digital map database, compiled from new mapping by the authors, represents
the general distribution of bedrock and surficial deposits of the Dixonville
7.5 minute quadrangle along the southeastern margin of the Oregon Coast Range
and its tectonic boundary with Mesozoic terranes of the Klamath Mountains.
Together with the accompanying text files as PDF (geol.pdf), it provides
current information on the geologic structure and stratigraphy of the area
covered. The database delineates map units that are identified by general age
and lithology following the stratigraphic nomenclature of the U.S. Geological
Survey. The scale of the source maps is 1:24,000. The spatial resolution
(scale) of the database is 1:24,000 or smaller.

Procedures_Used: The databases in this report were compiled in ARC/INFO, a
commercial Geographic Information System (Environmental Systems Research
Institute, Redlands, California, with version 3.0 of the menu interface
ALACARTE (Fitzgibbon and Wentworth, 1991, Fitzgibbon, 1991, Wentworth and
Fitzgibbon, 1991). The files are in either GRID (ARC/INFO raster data) format
or COVERAGE (ARC/INFO vector data) format. Coverages are stored in
uncompressed ARC export format (ARC/INFO version 8.0.2). ARC/INFO export files
(files with the .e00 extension) can be converted into ARC/INFO coverages in
ARC/INFO (see below) and can be read by some other Geographic Information
Systems, such as MapInfo via ArcLink and ESRI's ArcView (version 1.0 for
Windows 3.1 to 3.11 is available for free from ESRI's web site:
http://www.esri.com). The digital compilation was done in version 8.0.2 of
ARC/INFO with version 3.0 of the menu interface ALACARTE (Fitzgibbon and
Wentworth, 1991, Fitzgibbon, 1991, Wentworth and Fitzgibbon, 1991). The
geologic map information was digitized from stable originals of the geologic
maps at 1:24,000 scale. The author manuscripts (pen on mylar and pen on paper)
were scanned using a Ideal rasterizing color scanner with a resolution of 600
and 400 dots per inch. The scanned images were vectorized and transformed from
scanner coordinates to projection coordinates with digital tics placed by hand
at quadrangle corners. The scanned lines were edited interactively by hand
using ALACARTE, color boundaries were tagged as appropriate, and scanning
artifacts visible at 1:24,000 were removed.