George E. Gehrels
David S. Harwood
Gary H. Girty
M. J. Soreghan
George E. Gehrels
James P. Harding
2000
<p><span class="EXLDetailsDisplayVal">U-Pb analyses have been conducted on 92 individual <span class="searchword">detrital</span> <span class="searchword">zircon</span> grains from 4 of the main thrust sheets of the <span class="searchword">Shoo</span> <span class="searchword">Fly</span> <span class="searchword">Complex</span>. Samples from the Culbertson Lake allochthon, Duncan Peak allochthon, and Lang sequence yield mainly 1.80-2.10, 2.20-2.45, and 2.55-2.70 Ga ages, which suggests that sediments in these units originated in a cratonal region containing Paleoproterozoic and Archean igneous rocks. These ages match those of basement provinces from the northwestern Canadian shield, suggesting a provenance link with northwestern North <span class="searchword">America</span> during early <span class="searchword">Paleozoic</span> time. The <span class="searchword">Sierra</span> City melange, however, has significantly different <span class="searchword">zircon</span> ages of 551-635 and 1170-1319 Ma, with only a subordinate population of >1.8 Ga grains. These grains apparently were derived originally from an outboard Neoproterozoic-Cambrian(?) volcanic arc and from 1.0-1.7 Ga basement rocks of south-<span class="searchword">western</span> North <span class="searchword">America</span>. The occurrence of all three sets of ages in a sandstone that accumulated outboard of the Lang, Culbertson Lake, and Duncan Peak thrust sheets indicates that most rocks of the Shoo Fly Complex formed inboard of a volcanic arc located in proximity to the southern portion of the Cordilleran margin.</span> </p>
application/pdf
10.1130/0-8137-2347-7.43
en
American Geosciences Institute
Detrital zircon geochronology of the Shoo Fly Complex, northern Sierra terrane, northeastern California
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