Stratigraphy, sedimentology and petrology of neogene rocks in the Deschutes Basin, Central Oregon: a record of continental-margin volcanism and its influence on fluvial sedimentation in an arc-adjacent basin

Technical Report · Tue Jul 01 04:00:00 EDT 1986

OSTI ID:5216792

Smith, G A

Neogene rocks of the Deschutes basin include the middle Miocene Columbia River Basalt Group and Simtustus Formation, and late Miocene to early Pliocene Deschutes Formation. Assignment of Prineville chemical-type flows to the Grande Ronde Basalt of the Columbia River Basalt Group is based on correlation of these lavas from their type area through the Deschutes basin and onto the Columbia Plateau, where they have been previously mapped as Grande Ronde Basalt. Simtustus Formation is a newly defined unit intercalated with and conformable upon these basalts, and is unconformably overlain by Deschutes Formation. Burial of mature topography by middle Miocene basalts raised local base levels and initiated aggradation by low-gradient streams within the basin represented by the tuffaceous sandstones and mudstones of the Simtustus Formation. These sediments are enriched in pyroclastic constituents relative to contemporaneous Western Cascades volcanics, reflecting preferential incorporation of easily eroded and more widespread pyroclastic debris in distal sedimentary sequences compared to epiclastic contributions from lavas. The abundance of basalts, combined with the paucity of hydrous minerals and FeO and TiO/sub 2/ enrichment in intermediate lavas, characterizes early High Cascade volcanics as atypical for convergent-margin arcs. These petrologic characteristics are consistent with high-level fractionation in an extensional regime. Extension culminated in the development of an intra-arc graben, which ended Deschutes Formation deposition by structurally isolating the basin from the High Cascade source area.

• Research Organization: Rockwell International Corp., Richland, WA (USA). Rockwell Hanford Operations
• DOE Contract Number: AC06-77RL01030
• OSTI ID: 5216792
• Report Number(s): RHO-BW-SA-555-P; ON: DE86015436
• Country of Publication: United States
• Language: English

Related Subjects

052002 -- Nuclear Fuels-- Waste Disposal & Storage
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
CENOZOIC ERA
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGY
GEOMORPHOLOGY
NORTH AMERICA
OREGON
PETROLOGY
PLATE TECTONICS
ROCKS
SEDIMENTARY ROCKS
SEDIMENTATION
STRATIGRAPHY
TECTONICS
TERTIARY PERIOD
USA
VOLCANISM