Masters Thesis

Provenance of the Paleogene Goler Formation, southern California, and implications for basin development in the southwestern US Cordillera

The Paleogene Goler Formation, located east of the southern Sierra Nevada and north of the Garlock Fault, is one of the only basins in the southwestern US Cordillera that preserves early Cenozoic strata and uniquely records tectonic changes along the margin at that time. This study combines new and previously published detrital zircon (DZ) U-Pb analyses to evaluate temporal changes in provenance of the Goler Formation. The Goler Formation comprises about 3.5 km (stratigraphic thickness) of mainly siltstones, sandstones, and conglomerates. The lowest ~800m of strata reflect a complex age spectra dominated by Permian and Triassic peaks (241 and 253 Ma). The middle of the formation (~1200 - 2300 m) is dominated by Middle to Late Jurassic grains (87 - 93%) with a peak age of ca. 165 Ma. The remaining grains have Late Cretaceous ages (100 - 85 Ma). At about 2300 m of stratigraphic thickness a provenance change is recorded where the proportion of Late Cretaceous (87 - 100 Ma) grains increases (up to 35%), and age spectra become more complex; Middle to Late Jurassic grains span a broader range of ages (175 - 145 Ma) and additional subordinate Late Triassic - Early Jurassic populations (peak ages of ca. 195 Ma) are observed. Collectively, these DZ data suggest derivation of the lower Goler Formation from local El Paso Mountain and Argus Range sources to the east, transitioning through time to mixed-source which included the Sierra Nevada and Coso Range. These results align with a model of the Goler Basin forming in a Paleogene supra-detachment basin where provenance was limited to the hanging wall early in its history but switched to a mixed provenance as the footwall (Sierra Nevada) was exhumed.

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