U-Pb zircon data for Cenozoic clastic and volcaniclastic units deformed along the Gales Creek Fault zone, northwestern Oregon
April 5, 2023
This data release includes laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb zircon geochronology data from four samples collected from fault-bounded bedrock units in northwestern Oregon. Samples were collected from a paleoseismic trench excavated across the Scoggins Valley strand of the Gales Creek Fault and nearby quarry. The trench is located on a ridge top saddle on the Scoggins Creek-Tualatin River divide, where it crosses a lidar scarp trending 300°, up to the east, with suggestion of dextral slip. Trench trends 060° across scarp, is 35 m long in bedrock. Loess, paleosols, and colluvium overlie bedrock. The trench exposes tuffaceous sediments of the Keasey Formation, which records initial deposition of Cascade-derived sediment into the forearc basins from the newly formed Cascade arc. Three samples were collected in the trench from the tuffaceous mudstone of the Keasey Formation; the basaltic sandstone in the Stimson Mill member of the Keasey Formation, and a lithic sandstone bed in the Keasey Formation, respectively. One sample was collected from a quarry near the paleoseismic trench, in a 13m-thick, indurated silicic tuff bed of the Keasey Formation, which may correlate with one of the large, dated ash flow tuffs recognized in the Cascade arc and backarc between ~41 and 25 Ma. The sequence is capped with modern gray loess-derived soil of variable thickness. Ages of samples WN17-1, -2, and -7 overlap, and all have a large tuffaceous component from the initiation of Cascade arc volcanism. Sample WN17-6 has a slightly older detrital age spectra and is a dark brown weathered lithic (basaltic) sandstone, distinct from the three other light colored tuffaceous rocks. The tuff bed (sample WN17-7) is a local marker bed in the basaltic sandstone. The older age for the basaltic sandstone may reflect a separate Coast Range source. The data supports the geologic map of Scoggins Dam, Henry Hagg Lake, and the Scoggins Valley area, Washington County, Oregon.
Citation Information
Publication Year | 2023 |
---|---|
Title | U-Pb zircon data for Cenozoic clastic and volcaniclastic units deformed along the Gales Creek Fault zone, northwestern Oregon |
DOI | 10.5066/P91ZSKV3 |
Authors | Laura S Pianowski, Christopher S Holm-Denoma, Lydia M Staisch, Ray E Wells |
Product Type | Data Release |
Record Source | USGS Asset Identifier Service (AIS) |
USGS Organization | Geology, Geophysics, and Geochemistry Science Center |
Rights | This work is marked with CC0 1.0 Universal |
Related
Geologic map of Scoggins Dam, Henry Hagg Lake, and Scoggins Valley, Washington County, Oregon
New geologic mapping (Wells and others, 2020b) and geophysical mapping (Blakely and others, 2000; McPhee and others, 2014; Wells and others, 2020a) document kilometers of Cenozoic right-lateral offset along the Gales Creek Fault Zone, a major, northwest-striking fault zone forming the boundary between the Tualatin Valley and the Coast Range. The Bureau of Reclamation’s (Reclamation)...
Laura Pianowski
Email
Phone
Christopher Holm-Denoma
Research Geologist
Research Geologist
Email
Phone
Lydia M Staisch, Ph.D.
Research Geologist
Research Geologist
Email
Ray Wells
Research Geologist
Research Geologist
Email
Related
Geologic map of Scoggins Dam, Henry Hagg Lake, and Scoggins Valley, Washington County, Oregon
New geologic mapping (Wells and others, 2020b) and geophysical mapping (Blakely and others, 2000; McPhee and others, 2014; Wells and others, 2020a) document kilometers of Cenozoic right-lateral offset along the Gales Creek Fault Zone, a major, northwest-striking fault zone forming the boundary between the Tualatin Valley and the Coast Range. The Bureau of Reclamation’s (Reclamation)...
Laura Pianowski
Email
Phone
Christopher Holm-Denoma
Research Geologist
Research Geologist
Email
Phone
Lydia M Staisch, Ph.D.
Research Geologist
Research Geologist
Email
Ray Wells
Research Geologist
Research Geologist
Email