Neogene paleogeography of western Snake River plain, Idaho and Oregon

Conference · Sun Apr 01 00:00:00 EST 1984 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:6376465

Porter, M L; Middleton, L T

Analysis of Miocene through Pleistocene siliciclastic and volcaniclastic sequences in the western Snake River Plain of Idaho and Oregon allows detailed paleogeographic reconstruction of sedimentation associated with the development of a rapidly subsiding continental basin. Extensional tectonism was accompanied by voluminous outpourings of basaltic and silicic volcanic material. These in turn were reworked basinward by marginal alluvial fan-braided stream networks into basin-center fluviolacustrine systems. Episodic influxes of both felsic and basaltic tephra are recorded in fossiliferous lacustrine silt and claystones of the Poison Creek and Chalk Hills Formations, radiometrically bracketed between 12.5 to 5 m.y.B.P. Basinward-fining facies indicate deposition in the large lacustrine complex fed by at least 2 major fluvial systems. Complex interfingering of coarse-grained strandline deposits with offshore fine-grained sediments suggests repeated expansion and contraction of the lake system and record the dynamic interplay between basin tectonism and sedimentation.

• Research Organization: Univ. of Wisconsin, Madison
• OSTI ID: 6376465
• Report Number(s): CONF-8405216-
• Journal Information: Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 68:4; Conference: AAPG annual convention, San Antonio, TX, USA, 20 May 1984
• Country of Publication: United States
• Language: English

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