Detrital zircon facies of Cordilleran terranes in western North America

[摘要] Paleozoic–Mesozoic basins inCordilleran terranes of western North America contain detrital zircon U-Pb age distributionsthat vary over 10–100 Ma in a systematic and predictable manner. A minimum of fourdetrital zircon age distributions, here termed “detrital zircon facies,” are present:(1) Paleoproterozoic and Archean facies, chiefly found in Paleozoic and early Mesozoicaccretionary complexes, is defined by late Archean–early Proterozoic (ca. 2.7–2.3Ga) and late Proterozoic ages (ca. 2.0–1.6 Ga) with variable quantities of Paleozoicand early Mesozoic ages. (2) Mixed Proterozoic and Phanerozoic facies is found inEarly–Late Jurassic basins and is defined by grains spanning ca. 2.0 Ga–160 Ma,derived from eastern-southwestern Laurentian transcontinental sources and enrichedby western U.S. and eastern Mexican early Mesozoic plate-margin magmatism. (3) Triassicand Jurassic facies, found in Late Jurassic–Early Cretaceous basins, is definedby Late Jurassic ages (peak ca. 155 Ma) with a subordinate proportion of Triassicages (peak ca. 230 Ma). (4) Jurassic and Early Cretaceous facies is found in lateEarly–early Late Cretaceous marginal basins and is defined by Jurassic and EarlyCretaceous ages (ca. 200–130 and ca. 130–100 Ma). Detrital zircon U-Pb ages fromterranes of western North America record stages of basin formation during phasesof the supercontinent cycle and reflect second-order variability in the tectonicsetting of an active continental plate margin. At this temporal and spatial scale,the integrated evolution of orogenic, erosion, and sediment-transport systems controlssediment provenance.

[学科分类] 地质学

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