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The Upper Jurassic Galice Formation, a metasedimentary unit in the Western Klamath Mountains, formed within an intra-arc basin prior to and during the Nevadan orogeny. New detrital zircon U-Pb age analyses (N = 11; n = 2792) yield maximum depositional ages (MDA) ranging from ca. 160 Ma to 151 Ma, which span Oxfordian to Kimmeridgian time and overlap Nevadan contractional deformation that began by ca. 157 Ma. Zircon ages indicate a significant North American continental provenance component that is consistent with tectonic models placing the Western Klamath terrane on the continental margin in Late Jurassic time. Hf isotopic analysis of Mesozoic detrital zircon (n = 603) from Galice samples reveals wide-ranging εHf values for Jurassic and Triassic grains, many of which cannot be explained by a proximal source in the Klamath Mountains, thus indicating a complex provenance. New U-Pb ages and Hf data from Jurassic plutons within the Klamath Mountains match some of the Galice Formation detrital zircon, but these data cannot account for the most non-radiogenic Jurassic detrital grains. In fact, the in situ Cordilleran arc record does not provide a clear match for the wide-ranging isotopic signature of Triassic and Jurassic grains. When compiled, Galice samples indicate sources in the Sierra Nevada pre-batholithic framework and retroarc region, older Klamath terranes, and possibly overlap strata from the Blue Mountains and the Insular superterrane. Detrital zircon age spectra from strata of the Upper Jurassic Great Valley Group and Mariposa Formation contain similar age modes, which suggests shared sediment sources. Inferred Galice provenance within the Klamath Mountains and more distal sources suggest that the Galice basin received siliciclastic turbidites fed by rivers that traversed the Klamath-Sierran arc from headwaters in the retroarc region. Thus, the Galice Formation contains a record of active Jurassic magmatism in the continental arc, with significant detrital input from continental sediment sources within and east of the active arc. These westward-flowing river systems remained active throughout the shift in Cordilleran arc tectonics from a transtensional system to the Nevadan contractional system, which is characterized by sediment sourced in uplifts within and east of the arc and the thrusting of older Galice sediments beneath older Klamath terranes to the east.
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This content will become publicly available on November 1, 2026
Basement Domains Recorded in the Zircon Geochemistry of the Northern Sierra Nevada Batholith
Abstract The northern Sierra Nevada batholith was emplaced into and across a series of accreted crustal belts that vary considerably in their ages and lithologies. Unlike batholithic segments to the south, the northern Sierra comprises smaller, spatially distinct plutons where geologic relations with the host basement can be observed. Intermediate to felsic plutons were sampled as arc‐perpendicular transects at the latitude of Lake Tahoe and zircon Lu‐Hf and trace element analysis was performed in order to assess the relative impacts of temporal and spatial variability of arc magmatism on zircon geochemistry. Trends through time in the Hf data are complex, whereas there is an abrupt step from juvenile values in plutons intruding western belts (+12.3 to +14.4) to more evolved values in those intruding the Northern Sierra terrane to the east (−0.6 to +5.2). A similar pattern is observed in several zircon trace element signatures, including pronounced steps toward higher U/Yb, Dy/Yb and Ce/Y from the western belts into the Northern Sierra terrane to the east. The step is approximately coincident with the Feather River terrane, which is interpreted to mark the suture between the oceanic lithosphere to the west and the North American continental lithosphere to the east. The observed links between variation in zircon Lu‐Hf and trace element concentration and basement domain indicate that northern Sierran zircons incorporate, and are sensitive to, the crustal tracts into which they are emplaced. Preliminary application of our results to provenance analysis of Great Valley strata indicates changing provenance through time in the adjacent forearc.
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- PAR ID:
- 10659484
- Publisher / Repository:
- Wiley Periodicals LLC on behalf of American Geophysical Union
- Date Published:
- Journal Name:
- Geochemistry, Geophysics, Geosystems
- Volume:
- 26
- Issue:
- 11
- ISSN:
- 1525-2027
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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