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Contrasting early and late Mesozoic petrotectonic evolution of northern California

W.G. Ernst^,1, Cameron A. Snow¹ and Hannah H. Scherer¹

¹ Stanford University, Geological and Environmental Sciences, Building 320, Room 118, Stanford, California 94305-2115, USA

View larger version (67K): [in this window] [in a new window]   Figure 1. Geology of northern California, generalized after U.S. Geological Survey and California Division of Mines and Geology (1966).

View larger version (51K): [in this window] [in a new window]   Figure 2. Geologic map showing terranes of the Klamath Mountains, generalized after Irwin (1994) and Irwin and Wooden (1999). Most terrane boundaries are east-rooting thrust faults. Abbreviations for subterranes are as follows: E—Eastern Hayfork, R—Redding, T—Trinity, W—Western Hayfork, Y—Yreka. SCR—Soap Creek Ridge thrust fault. The Wilson Point thrust (dashed line) juxtaposes Eastern and Western Hayfork subterranes (Wright, 1982), but is not labeled on this simplified compilation.

View larger version (26K): [in this window] [in a new window]   Figure 3. Probability density plots of detrital zircon U-Pb data from North Fork distal turbidites (Scherer and Ernst, 2008). (A) Southern Hayfork Summit area. (B,C) Central Sawyers Bar area.

View larger version (22K): [in this window] [in a new window]   Figure 4. Relative probability-density plots of detrital zircon U-Pb data for sandstone blocks from: (A) the central and southern Klamath Eastern Hayfork terrane (Scherer, 2006); (B) the Antelope Mountain Quartzite, Eastern Klamath Mountains (Wallin et al., 2000); (C) the Harmony Formation, Roberts Mountains allochthon (RMA) (Gehrels et al., 2000a); (D) the Lang-Duncan Peak-Culbertson Lake (LDC) allochthon of the Shoo Fly Complex, Northern Sierra terrane (NST) (Harding et al., 2000); (E) the Picayune Valley Formation of the Northern Sierra terrane (Spurlin et al., 2000).

View larger version (35K): [in this window] [in a new window]   Figure 5. Geologic map showing major terranes and faults of the Sierra Nevada Foothills metamorphic belt (generalized after Edelman and Sharp, 1989; Irwin and Wooden, 1999). Most terrane boundaries are high-angle reverse faults. BBF—Big Bar fault, BMF—Bear Mountain fault, CSFT—Calaveras–Shoo Fly thrust, DF—Downieville fault, DPF—Dogwood Peak fault, GCF—Goodyears Creek fault, GHF—Gillis Hills fault, GM—Grizzly Mountain thrust, HCW—Higgins Corner window, LOW—Lake Oroville window, MF—Melones fault, RBF—Rich Bar fault, SF—Sonora fault, SPF—Spencerville fault, STF—Slate Creek thrust, TT—Taylorsville thrust, UF1—unnamed fault 1.

View larger version (20K): [in this window] [in a new window]   Figure 6. Detrital zircon U-Pb age histograms and superimposed relative-probability curves for five specimens of Mariposa sandstone, each plotted at two scales to highlight the Mesozoic age distributions (Snow and Ernst, 2008). All ages are plotted from 0 to 3500 Ma, with Mesozoic ages plotted from 125 to 225 Ma. The lower four panels are for strata near the base of the Mariposa Formation; PB158A was selected upsection from these four samples.

View larger version (27K): [in this window] [in a new window]   Figure 7. Relative probability-density distribution plots showing only pre-Mesozoic zircons. All pre-200 Ma grains were combined to show the full range represented by the five analyzed Mariposa sandstones samples. References for other detrital zircon distributions are: Bragdon and Baird formations, Eastern Klamath terrane, Gehrels and Miller (2000); Antelope Mountain Quartzite, Wallin et al. (2000); Shoo Fly Complex, Harding et al. (2000); Shoo Fly Overlap, Spurlin et al. (2000); Golconda allochthon, Riley et al. (2000); Antler Overlap, Gehrels and Dickinson (2000); Roberts Mountain allochthon, Gehrels et al. (2000); Black Rock terrane, Darby et al. (2000); Paleozoic Nevada miogeocline; Gehrels et al. (1995).

View larger version (27K): [in this window] [in a new window]   Figure 8. Speculative model for Jurassic plate tectonic evolution of northern California. (A) Transpressive docking of the Eastern Hay-fork–Calaveras amalgam ca. 205–195 Ma. (B) Rifting in the medial Klamath terrane assembly with oceanic crust produced or tectonically inserted both outboard (Rattlesnake Creek) and inboard (North Fork) relative to the Eastern Hayfork terrane ca. 190–165 Ma. (C) Transpression and sedimentation of the Galice-Mariposa formations prior to westward extrusion of the Klamath salient, immediately followed by westward step out of a new convergent plate junction ca. 155–145 Ma. Subduction-generated massive volcanism-plutonism during middle and Late Cretaceous (K) time produced an Andean-type calc-alkaline arc east of the Sierran Foothills (red dashed line shows trend of this ca. 120–85 Ma batholith, after compilation of Irwin, 2003); the northern extension of the batholith apparently lay to the east of the Klamath salient, but has been obscured by overlying Cenozoic rocks of the Cascade and Modoc Plateau provinces.