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Geologic map and database of the Salem East and Turner 7.5-minute quadrangles, Marion County, Oregon: a digital database

Open-File Report 2000-351

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Abstract

The Salem East and Turner 7.5-minute quadrangles are situated in the center of the Willamette Valley near the western margin of the Columbia River Basalt Group (CRBG) distribution. The terrain within the area is of low to moderate relief, ranging from about 150 to almost 1,100-ft elevation. Mill Creek flows northward from the Stayton basin (Turner quadrangle) to the northern Willamette Valley (Salem East quadrangle) through a low that dissects the Columbia River basalt that forms the Salem Hills on the west and the Waldo Hills to the east. Approximately eight flows of CRBG form a thickness of up to 700� in these two quadrangles. The Ginkgo intracanyon flow that extends from east to west through the south half of the Turner quadrangle is exposed in the hills along the southeast part of the quadrangle.


Previous geologic mapping by Thayer (1939) and Bela (1981) while providing the general geologic framework did not subdivide the CRBG which limited their ability to delineate structural elements. Reconnaissance mapping of the CRBG units in the Willamette Valley indicated that these stratigraphic units could serve as a series of unique reference horizons for identifying post-Miocene folding and faulting (Beeson and others, 1985,1989; Beeson and Tolan, 1990). Crenna, et al. (1994) compiled previous mapping in the Willamette Valley in a study of the tectonics of the Salem area.


The major emphasis of this study was to identify and map CRBG units within the Salem East and Turner Quadrangles and to utilize this detailed CRBG stratigraphy to identify and characterize structural features. Water well logs were used to provide better subsurface stratigraphic control. Three other quadrangles (Scotts Mills, Silverton, and Stayton NE) in the Willamette Valley have been mapped in this way (Tolan and Beeson, 1999).


This area was a lowland area of weathered and eroded marine sedimentary when the Columbia River basalts encroached on this area approximately 15-16 m.y. ago. An incipient Coast Range apparently stopped or diverted the fluid lava flows from moving much farther westward toward the coast at this latitude. It is assumed also that an ancestral Willamette River flowed northward through this low-lying area so that water was present as streams and ponds along the flood plain.

Study Area

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Geologic map and database of the Salem East and Turner 7.5-minute quadrangles, Marion County, Oregon: a digital database
Series title:
Open-File Report
Series number:
2000-351
Year Published:
2000
Language:
English
Publisher:
U.S. Geological Survey
Contributing office(s):
National Cooperative Geologic Mapping Program
Description:
Salem East Quad: 30.93 x 35.04 inches; Turner Quad: 31.73 x 35.20 inches; Maps: TAR.Z file; Database: TAR.Z file; Database: ZIP file; Readme: DOC file; Readme: TXT; Readme: PDF file
Country:
United States
State:
Oregon
County:
Marion County
Other Geospatial:
Mill Creek;Willamette Valley
Projection:
Universal Transverse Mercator projection
Scale:
24000
Additional Online Files(Y/N):
Y