Record Details
Bedrock geology and structure of the Murderers Creek Area, Grant County, Oregon
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Bedrock geology and structure of the Murderers Creek Area, Grant County, Oregon |
| Names |
Stockman, Alan Owen
(creator) Lawrence, Robert D. (advisor) |
| Date Issued | 1981-06-08 (iso8601) |
| Note | Graduation date: 1982 |
| Abstract | The Murderers Creek Area, within the Aldrich Mountain province of northeast Oregon, originated in an arc-trench gap during Permian-early Triassic time. The area represents a small portion of a forearc depositional basin and tectonic highland which borders the basin along its seaward margin. The trench associated with an east dipping subduction was located to the northwest of the area, bordering the melange highland. The rocks of the Murderers Creek Area are divided into pre-Tertiary and Tertiary rock assemblages on the basis of genetic differences. The pre-Tertiary rock assemblage reflects an active subduction of oceanic lithosphere in an island arc environment isolated from the North American craton. This assemblage of rocks includes: (1) a melange (Permian-Triassic) of ophiolitic peridotites, gabbros, greenstones, cherts, and argillites encased in a highly sheared serpentine matrix; (2) the Vester Formation (Karnian) containing lutites, greywackes, olistostromal blocks, and minor tuffs, derived for the most part from the melange and deposited in a forearc basin formed by the uplift of the melange terrain; (3) the Fields Creek Formation (Norian) including siliceous lutites, greywackes, and large olistostromal masses all derived from the uplifted melange and Vester Formation and deposited in a forearc basin together with injected submarine lavas and arc derived tuffs; and (4) the Fields Peak stock (upper Jurassic-lower Cretaceous) granodiorite to tonalite in composition, representing part of the intrusive event which marked the effective consolidation of the island arc province to the North American craton. The post-Cretaceous rock assemblage reflects a relatively stable cratonic margin and includes: (1) the Clarno Formation (Eocene) volcanic mudflows and breccias; (2) the Columbia River Group (middle Miocene) flood basalts; (3) basalts and glacial terrace gravels (Quaternary). Structurally the Murderers Creek Area has a two stage character with early structures (Permian through Jurassic) related to an east-west compression of the area associated with the subduction of oceanic lithosphere, and with late structures (Cretaceous through Recent) associated with stresses affecting a relatively stable cratonic margin. Early structures include: (1) a northeast to northwest shearing of the melange terrain, following the arcuate trend of the unit, (2) tight isoclinal folding of the Vester Formation along northeast axes, (3) tight isoclinal folding of the Fields Creek Formation and cross folding of the Vester Formation along north to northwest axes also following the arcuate trend of the units. |
| Genre | Thesis/Dissertation |
| Topic | Petrology -- Oregon -- Murderers Creek Region (Grant County) |
| Identifier | http://hdl.handle.net/1957/41890 |
