Detrital zircon facies of Cordilleran terranes in western North America
Search GoogleScholar for
Search GSA Today
Paleozoic–Mesozoic basins in Cordilleran terranes of western North America contain detrital zircon U-Pb age distributions that vary over 10–100 Ma in a systematic and predictable manner. A minimum of four detrital zircon age distributions, here termed “detrital zircon facies,” are present: (1) Paleoproterozoic and Archean facies, chiefly found in Paleozoic and early Mesozoic accretionary complexes, is defined by late Archean–early Proterozoic (ca. 2.7–2.3 Ga) and late Proterozoic ages (ca. 2.0–1.6 Ga) with variable quantities of Paleozoic and early Mesozoic ages. (2) Mixed Proterozoic and Phanerozoic facies is found in Early–Late Jurassic basins and is defined by grains spanning ca. 2.0 Ga–160 Ma, derived from eastern-southwestern Laurentian transcontinental sources and enriched by western U.S. and eastern Mexican early Mesozoic plate-margin magmatism. (3) Triassic and Jurassic facies, found in Late Jurassic–Early Cretaceous basins, is defined by Late Jurassic ages (peak ca. 155 Ma) with a subordinate proportion of Triassic ages (peak ca. 230 Ma). (4) Jurassic and Early Cretaceous facies is found in late Early–early Late Cretaceous marginal basins and is defined by Jurassic and Early Cretaceous ages (ca. 200–130 and ca. 130–100 Ma). Detrital zircon U-Pb ages from terranes of western North America record stages of basin formation during phases of the supercontinent cycle and reflect second-order variability in the tectonic setting of an active continental plate margin. At this temporal and spatial scale, the integrated evolution of orogenic, erosion, and sediment-transport systems controls sediment provenance.
Manuscript received 2 Nov. 2011; accepted 6 Jan. 2012.