Late Cretaceous to early Eocene geologic evolution of the U.S. Cordillera

Understanding a critical basinal link in Cretaceous Cordilleran paleogeography: Detailed provenance of the Hornbrook Formation, Oregon and California

“…1 and 2; Nilsen, 1993). Dominantly north-and northeast-directed paleocurrent indicators, together with sandstone petrography, have been interpreted to indicate a Klamath Mountains source of sediment (Nilsen, 1984(Nilsen, , 1993Miller et al, 1992). We present the results of sandstone petrography, detrital zircon U-Pb age and Hf isotopic systematics, and whole-rock Nd analysis throughout the Hornbrook Formation to provide a more detailed and complete provenance signature that records changing sediment sources through time.…”

“…The Hornbrook Formation has been considered the northern extension of the Cretaceous Great Valley Group forearc basin (Nilsen, 1984;Miller et al, 1992), and both basins responded to Late Cretaceous tectonic events. The results of our provenance analysis suggest that the two basins shared a similar source in the Klamath Mountains in early Late Cretaceous time, but were not linked into a single depositional system until Santonian time, when sediment sources for both basins shifted to the east, concomitant with uplift in eastern sources and continued subsidence and relative sea-level rise in the expanding Hornbrook-Great Valley forearc basin.…”

“…Lithotectonic belts of the Sierran Foothills terranes form a complex assemblage of Paleozoic and early Mesozoic arc-related terranes and subduction complexes, and are composed of serpentinized ultramafi c rocks, blueschists, chert-argillite-limestone mélange, metasedimentary rocks, and ophiolites ( Fig. 10; Miller et al, 1992, and references therein; Snow and Scherer, 2006;Ernst et al, 2008). These accretionary belts were intruded by plutonic rocks at 205-200 Ma, 173-155 Ma, 142-136 Ma, and 133 Ma (Irwin, 2003, and references therein).…”

“…1; e.g., Burchfi el et al, 1992;Dickinson, 2004). During the Late Cretaceous, the Blue Mountains, Sierra Nevada Mountains, and Klamath Mountains may have been part of a single, relatively continuous magmatic arc, with the forearc basins associated with these mountain ranges forming one complex forearc basin along the west coast of North America (Nilsen, 1984;Miller et al, 1992). Wyld et al's (2006) 100 Ma reconstruction restores displacement on faults active since 100 Ma, as well as displacements within Late Cretaceous and Cenozoic contractional and extensional belts, bringing the Ochoco and Hornbrook basins together into one connected system, and suggesting that the Methow basin may represent the northern continuation of the combined Hornbrook-Ochoco basin.…”

Effect of predeformational basin geometry in the kinematic evolution of a thin‐skinned orogenic wedge: Insights from three‐dimensional finite element modeling of the Provo salient, Sevier fold‐thrust belt, Utah

“…[7] The Provo salient ( Figure 1a) in central Utah is part of the Sevier fold-thrust belt that defines the eastern margin of thin-skinned crustal shortening in the Cordilleran orogen of western North America [Armstrong, 1968;Burchfiel and Davis, 1975;Allmendinger, 1992;Miller et al, 1992]. It is an example of a ''basin-controlled salient'' [Macedo and Marshak, 1999] based on the close relationship between its prominent map view arcuate shape and the restored basin geometry of the Provo salient [Paulsen and Marshak, 1999].…”