Middle-Late Ordovician Quartzites of Western North America: Local and Distant Source Areas

The Middle to Late Ordovician Eureka Quartzite (and its equivalents) is a unique orthoquartzite deposited along the otherwise carbonate-dominated Lower Paleozoic passive margin of the western North American Cordillera. A north to south decrease in grain size and increase in sediment sorting (Ketner, 1968), and previous detrital zircon provenance studies (Gehrels et al., 1995; Gehrels and Dickinson, 1998; Gehrels, 2000) are interpreted to indicate that the sole source of siliciclastic sediment for these units is the Peace River Arch, British Columbia. This single-source, long-distance transport model, suggests sediment was transported over 2000 km by southerly long-shore currents along the passive margin, and that potentially exposed basement source areas on the Transcontinental Arch east of the passive margin, as well as recycling of underlying Mesoproterozoic to Lower Paleozoic siliciclastic rocks supplied little or no detritus to these sediments.

New U-Pb geochronologic analyses of Middle to Late Ordovician Kinnikinc Quartzite, Idaho, and Late Ordovician Cable Canyon Sandstone, New Mexico detrital zircons by the LA-ICPMS, provide a test for the single-source long-distance transport model. The Middle-Late Ordovician Kinnikinic Quartzite in east-central Idaho was deposited directly on Early Ordovician plutons and Mesoproterozoic metasedimentary rocks. The basal Kinnikinic Quartzite locally contains abundant 1.6-1.7 Ga detrital zircons interpreted to be recycled from the Mesoproterozoic metasedimentary rocks upon which they were deposited. Additionally, samples south of the Snake River Plain contain predominantly Archean (2.6-2.8 Ga) grains derived from the Wyoming Craton. The Cable Canyon Sandstone contains some 1.4 Ga, and many 1.6-1.7 Ga grains interpreted to indicate local anorogenic granites and Yavapai-Matzatzal terranes, respectively, exposed along the Transcontinental Arch. Detrital zircon analyses indicates local sources as well as the Talson-Thelon Orogen (widespread abundance of 1.8 Ga zircons) are the main sediment sources in the western Cordillera during deposition of Middle to Late Ordovician quartzites.