87 Presentaciones de Geociencias en Español: Continuamos con la experiencia en la GSA 2025/Geoscience Presentations in Spanish: Continuing the Experience at GSA 2025, Part I

This session invites Geosciences presentations in Spanish at all proficiency levels; abstracts can be submitted in English or Spanish and they do not count towards the GSA’s limit of one abstract oral presentation per person.

Monday, 20 October 2025
8:00 AM - 12:00 PM
HBGCC, 217B

The Transverse Ranges Arc: The missing link between southwest Laurentia and eastern Antarctica?

Paper number: 87-1
Program: Technical Sessions
Time: 8:05 AM – 8:20 AM

Authors

Abstract

Laurentia constitutes the core of two major Proterozoic supercontinents (Rodinia and Columbia), yet much debate remains on intercontinental connections, notably regarding the western margin. The Mojave crustal province (“Mojavia” of Bennett and DePaolo, 1987) is a key piercing point in all geologic based models, from SWEAT (southwest Laurentia-eastern Antarctica) to the Siberia connection. Despite the importance of Mojavia in Proterozoic paleogeography, most geochemical studies have been focused away from its southwestern margin. Here, we present new U-Pb geochronology and zircon Hf-Lu geochemistry from Paleoproterozoic gneisses in the western Transverse Ranges of southern California and compare our results with data from Wooden et al. (2012), Holland et al. (2018), and proposed continental matches (e.g., eastern Antarctica). Based on our data, we propose a new tectonic block, the “Transverse Ranges Arc”, a sliver of 1.8-2.0 Ga continental crust today found in locations including Frazier, Liebre, and San Gabriel Mountains that we incorporate into a model for Mojavia and Antarctic interaction. 

Ongoing work by the California State Geologic Survey has identified a suite of 1.8-2.0 Ga orthogneisses scattered across various segments of the Transverse Ranges in southern California. This age population is notably absent in eastern Mojavia apart from metasediments and the 1.84 Ga Elves Chasm Gneiss, exposed only in the Grand Canyon. Our study obtained an 1810±24 Ma U/Pb age and inherited components in younger orthogneisses have ages around ~1800 Ma. Lutetium-Hf isotope geochemistry of these zircon populations yielded weighted mean eHf(i) of +2.2 to +6.9, much more juvenile than the -4.1 to -0.9 range of early plutons (~1.79 Ga) in the Mojave interior. In contrast, younger orthogneisses (1754-1690 Ma) yielded eHf(i) compositions (-0.5 to +5.7) similar to other parts of Mojavia, suggesting the two areas have a shared tectonic history after 1.8 Ga. eHf(i) values from ~1.4 to 1.6 Ga zircon rims with similar composition to age-equivalent clasts in eastern Antarctica also support a stable long-lived SWEAT configuration since 1.8 Ga.

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

doi: 10.1130/abs/2025AM-414081

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