Detrital zircon dating
Detrital zircon dating
Thus, rocks bearing PPA facies may reflect sediment derivation from northwestern Laurentian sources enhanced by plate-margin magmatism or multicycle sediment reworking and tectonic translation of crustal fragments allochthonous to western North America.Regardless of the ultimate source of age-characteristic zircon grains, PPA facies sand was present in arc-basin complexes on the western North American plate margin by mid-Paleozoic time (Harding et al., 2000; Spurlin et al., 2000; cf.
These age distributions vary systematically based on the depositional age and tectonic setting of the basin (cf. Figure 1 Map illustrating present-day location of terranes discussed in this paper, age distribution of Laurentian Precambrian crust, and detrital zircon sample locations: SEYTT—Southeastern Yukon-Tanana terrane; YTT-CM—Yukon-Tanana terrane in Coast Mountains; GRAV—Gravina Belt; MT—Methow-Tyaughton; EFLC—Easton-Fidalgo-Lummi-Constitution; YA—Yellow Aster; IG—Ingalls Graywacke; T-N—Tonga-Nooksack; LM—Lookout Mountain; CH—Coon Hollow; BT—Baker terrane; MI—Mitchell Inlier; SL—Snowshoe and Lonesome fms.; KRC—Klamath River Conglomerate; GAL—Galice; AMQ—Antelope Mountain Quartzite; EHT—Eastern Hayfork terrane; NFT—North Fork terrane; U-GVG—Upper Great Valley Group; T-GVG—“Tithonian” Great Valley Group; LDC-P—Lang-Duncan-Culberton allochthons and Picayune Valley Fm.; M-GVG—Middle Great Valley Group; MAR—Mariposa; JEK—Jurassic–Early Cretaceous; MPP—Mixed Proterozoic and Phanerozoic; and PPA—Paleoproterozoic and Archean. Adapted from Gehrels (2001); Wyld and Wright (2001); De Graaff-Surpless et al. (2006); Brown and Gehrels (2007); Nelson and Gehrels (2007); base modified from Whitmeyer and Karlstrom (2007).
My compilation, observations, and interpretations are specific to the time frame in this geographic range only; they are not intended to be a comprehensive review of Cordilleran provenance and tectonics, but rather, to serve as a starting point for continued investigation at this scale.
The overwhelming fundamental observation from the data is that regardless of interpreted terrane association, at a stratigraphic scale of 10–100 Ma, distinct age distributions are present in the same stratigraphic order along strike of the western North American margin.
(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. and eastern Mexican early Mesozoic plate-margin magmatism.
Noteworthy, non-PPA age distributions in Paleozoic accretionary-subduction complexes of the Klamath Mountains and Sierra Nevada may represent exotic crust, structurally intercalated with PPA-bearing rocks, or may suggest other explanations (e.g., Harding et al., 2000; Wright and Wyld, 2007; Grove et al., 2008). The presence of a transcontinental signature in each of these Early–Late Jurassic basins (Fig. Izsak et al., 2007; Dickinson and Gehrels, 2008a, 2009; La Maskin et al., 2011) suggests proximity to North America and the modern southwestern U. in early Mesozoic time, and that active orogenic structures and the plate-margin arc itself were not barriers to sediment transfer from the craton to the arc.
The age distribution in MPP facies represents transcontinental sand shed from the greater Ouachita-Appalachian orogeny and enriched by southwestern Laurentian sources, as well as early Mesozoic, plate-margin magmatism in the western U. Existing data suggest that these transcontinental sediments were not incorporated into western North American peripheral-arc systems until Early Jurassic time (Fig. 190–185 Ma, Klamath Mountains, North Fork terrane) (Scherer and Ernst, 2008). Lindsley-Griffin et al., 2006), and was subsequently recycled along the margin (Fig.4) (e.g., Scherer et al., 2010; La Maskin et al., 2011). Dickinson and Gehrels, 2003, 2009; Rahl et al., 2003).(3) Triassic and Jurassic facies, found in Late Jurassic–Early Cretaceous basins, is defined by Late Jurassic ages (peak ca. 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.155 Ma) with a subordinate proportion of Triassic ages (peak ca. (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. At this temporal and spatial scale, the integrated evolution of orogenic, erosion, and sediment-transport systems controls sediment provenance.It is not clear why transcontinental sediment was not delivered to arc-basin systems of the western U. during late Paleozoic time coincident with onset of the Alleghanian orogeny in eastern Laurentia (Hatcher, 2010).