Early Mesozoic paleogeography and tectonic evolution of the western United States: Insights from detrital zircon U-Pb geochronology, Blue Mountains Province, northeastern Oregon

Abstract

This study assesses early Mesozoic provenance linkages and paleogeographic-tectonic models for the western United States based on new petrographic and detrital zircon data from Triassic andJurassic sandstones of the "Izee" and Olds Ferry terranes of the Blue Mountains Province, northeastern Oregon. Triassic sediments were likely derived from the Baker terrane offshore accretionary subduction complex and are dominated by Late Archean (ca. 2.7-2.5 Ga), Late Paleo proterozoic (ca. 2.2-1.6 Ga), and Paleozoic (ca. 380-255 Ma) detrital zircon grains. These detrital ages suggest that portions of the Baker terrane have a genetic affinity with other Cordilleran accretionary subduction complexes of the western United States, including those in the Northern Sierra and Eastern Klamath terranes. The abundance of Precambrian grains in detritus derived from an offshore complex highlights the importance of sediment reworking. Jurassic sediments are dominated by Mesozoic detrital ages (ca. 230-160 Ma), contain significant amounts of Paleozoic (ca. 290, 380-350, 480-415 Ma), Neoproterozoic (ca. 675-575 Ma), and Mesoprotero zoic grains (ca. 1.4-1.0 Ga), and have lesser quantities of Late Paleoproterozoic grains (ca. 2.1-1.7 Ga). Detrital zircon ages in Jurassic sediments closely resemble well-documented age distributions in transcontinental sands of Ouachita-Appalachian provenance that were transported across the southwestern United States and modified by input from cratonal, miogeoclinal, and Cordilleran-arc sources during Triassic and Jurassic time. Jurassic sediments likely were derived from the Cordilleran arc and an orogenic highland in Nevada that yielded recycled sand from uplifted Triassic backarc basin deposits. Our data suggest that numerous Jurassic Cordilleran basins formed close to the Cordilleran margin and support a model for moderate post-Jurassic translation (~400 km) of the Blue Mountains Province.

East-derived strata in the Methow basin record rapid mid-Cretaceous uplift of the southern Coast Mountains batholith

“…Terranes of the Blue Mountains province include a Permian island-arc sequence overlain by Triassic volcanic and volcaniclastic rocks, a Middle to Late Triassic island-arc assemblage containing mostly andesitic volcanic rocks with intercalated sedimentary rocks, disrupted fragments of ocean floor, island-arc volcanic, plutonic, and sedimentary rocks ranging in age from Middle Devonian to Early Jurassic, and a Triassic-Jurassic sedimentary overlap succession that contains abundant Precambrian detrital zircon (Vallier 1995;LaMaskin et al 2008LaMaskin et al , 2011Schwartz et al 2010). The Blue Mountains Province is intruded by Triassic, Jurassic, and Cretaceous plutons ranging in age from ca.…”

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

“…Detrital zircon rarely occurs in samples lacking detrital quartz (Gehrels et al, 2006), and most detrital zircon is derived from felsic to intermediate igneous rocks and recycled clastic sedimentary or metasedimentary successions (Gehrels, 2000;Dickinson and Gehrels, 2009b;LaMaskin et al, 2011).…”

“…Terranes of the Blue Mountains Province include Paleozoic and early Mesozoic island-arc and subduction-accretion assemblages that are unconformably overlain by Triassic-Jurassic clastic deposits ( Fig. 10; Dickinson and Thayer, 1978;Dorsey and LaMaskin , 2007;LaMaskin et al, 2008 Lallemant, 1995;LaMaskin et al, 2011;Schwartz et al, 2011). Therefore, if the Blue Mountains remained a topographic high that shed sediment to the west and northwest during Cretaceous time, any catchment area would likely include these widespread sedimentary units, and resulting detrital zircon grains would refl ect derivation from both plutonic sources and recycled sedimentary sources.…”

“…5). LaMaskin et al (2011) noted that Early Jurassic plutons are not common in the U.S. Cordillera and concluded that Early Jurassic grains found in Middle and Upper Jurassic strata within the Blue Mountains Province were derived from the Black Rock terrane or recycled through Jurassic erg deposits. The Early Jurassic grains in the Osburger Gulch Sandstone thus may also be derived from the Black Rock terrane.…”

The Weberg and Warm Spring members of the Snowshoe Formation in Suplee area, Oregon: Lithofacies and Aalenian-early Bajocian ammonoid zonation

“…Tectonic settings for the Snowshoe Formation have been proposed among others by DICKINSON & THAYER (1978) and DICKINSON (1979). A current proposal is that the formation is part of a large successor or collisional basin (DORSEY & LAMASKIN, 2007;LAMASKIN et al, 2009LAMASKIN et al, , 2011, with a suggested accretion to the North America craton prior to Late Jurassic time (LAMASKIN et al, 2015). TAYLOR et al (1984) discussed Jurassic ammonoid provincialism, tectonostratigraphic terranes, and the inferred relative displacement of terranes with respect to one another and the craton.…”