32-7 Age and Provenance of the Winterhaven Formation, southeastern California

Session: Latest Research Advances in Structural Geology and Tectonics (Posters)

Presenting Author:

Authors:

Abstract:

The Winterhaven Formation is a succession of variably metamorphosed volcanic and clastic sedimentary rocks exposed in the eastern Chocolate Mountains, north of Yuma, Arizona.  The age, sediment provenance, tectonic setting of deposition, and relation to other sedimentary deposits of the unit has been uncertain.  We collected a sandstone sample from the Winterhaven Formation in the Picacho State Recreation Area, California for zircon U-Pb LA-ICP-MS geochronology and zircon Lu-Hf isotopic analyses to help resolve these questions.  The Winterhaven Formation sample analyzed has a maximum depositional age of 119.7 ± 1.1 Ma (2σ, MSWD = 1, n=10), suggesting it was deposited during the Early Cretaceous.  The population of detrital zircon dates contains two prominent age peaks at ca. 121 Ma and ca. 148 Ma.  The maximum depositional age and age peaks in the Winterhaven Formation sample are similar to published detrital zircon date populations from the lower McCoy Mountains Formation, which outcrops ~75 km north of the study area.  The Winterhaven Formation sample also yielded 5 Archean (> 2.5 Ga) dates that exhibited minor discordance.  Zircons from the 121 Ma age peak have εHf(t) values ranging from of -4 to +6, with an average of εHf(t)= +2 (n=9).  Zircons from the 148 Ma age peak have εHf(t) values ranging from of -18 to +1 (n=10).  The Archean zircons have εHf(t) values ranging from -8 to +11.  There are relatively few known locations of ca. 120 Ma igneous rocks with juvenile isotopic compositions in the southern U.S. Cordillera.  We interpret the ca. 120 Ma detrital zircons to have originated in the western Sierra Nevada batholith (e.g., Fine Gold Intrusive Suite) or western Peninsular Ranges batholith (e.g., Western Zone).  This interpretation implies the Winterhaven Formation had a sediment source located to the west and that the sediment may have traversed the Jurassic to early Cretaceous arc. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7577

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