204 Paleozoic Tectonics of SW Laurentia Without Borders: Final Amalgamation of Pangea in the USA, Mexico, and South America

We invite contributions that explore the Paleozoic tectonic evolution of southwestern Laurentia during the final assembly of western Pangea. Research on Paleozoic tectonic belts in Gondwana, particularly from Mexico and South America, is especially welcome.

Tuesday, 21 October 2025
1:30 PM - 5:30 PM
HBGCC, 217B

Stratigraphic and provenance variations in the Pennsylvanian Bird Spring and Keeler Basins, east-central California: Implications for Ancestral Rocky Mountain tectonism and continental-scale paleodrainage patterns

Paper number: 204-6
Program: Technical Sessions
Time: 2:55 PM – 3:10 PM

Authors

Abstract

In east-central California and southern Nevada, outcrops of the Pennsylvanian Bird Spring and Keeler Canyon formations preserve the southwestern most stratigraphic record of key late Paleozoic climatic, tectonic, and eustatic changes occurring along the western Laurentia margin. Previous work in the Bird Spring Shelf and Keeler Basin established regional facies trends and deposystem interpretations; however, existing stratigraphic correlations and geochronological data leave unanswered questions pertaining to temporal and spatial provenance shifts, governing tectonic regimes and ties to continental-scale paleodrainage patterns. Here, we present a basin-scale sedimentological, stratigraphic, and geochronological framework along a shelf-to-basin transect of carbonate platform strata on the Bird Spring Shelf to mixed carbonate-siliciclastic deep-water strata in the Keeler Basin. U-Pb detrital zircon results (N=15, n=2989) reveal two provenance trends: (1) Late Mississippian-Early Pennsylvanian strata display peak age modes at 0.42-0.46 Ga and 1.0-1.4 Ga, and 2) Middle-Late Pennsylvanian strata exhibit increased detrital zircon proportions of 1.6-1.7 Ga and minor proportions of 0.42-0.46 Ga and 0.0-1.4 Ga zircons. Top-down forward mixture modeling (detritalPy-mix) results show Upper Mississippian-Lower Pennsylvanian strata in the Bird Spring and Keeler basins sourced from Acadian/Taconic, northern Appalachian, and recycled Franklinian-Ellesmerian sources, but Middle-Upper Pennsylvanian strata sourced from 1.6-1.7 Ga basement cored uplifts associated with the Ancestral Rocky Mountain (ARM) orogen. Paleocurrents from shelf and slope strata at Arrow and Marble canyons indicate a west-northwestward paleoflow, whereas basinal strata observed in the Inyo Mountains indicate south-southwestward paleoflow. We interpret strata along the Bird Spring Shelf and Keeler Basin sourced from westward-oriented fluvial drainage networks with headwaters in the Acadian, Taconic and Grenville orogens. ARM orogenesis during the Middle Pennsylvanian deflected fluvial paleodrainage networks north of the ARM uplifts and likely resulted in the increased proportions of Paleoproterozoic detritus delivered to western Laurentian margin. This study also implies the southwestern extent of the Antler orogen was not an important sediment source for Bird Spring Shelf and Keeler Basin despite its proximity to those basins compared to more distal, eastern sources in the ARM and Grenville orogens. We attribute these new results along the Bird Spring-Keeler Basin transect to record the final remnants of the Paleozoic passive margin system along western Laurentia, representing the southwestern-most ‘sink’ of a +4000 km Laurentian paleodrainage network.

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

doi: 10.1130/abs/2025AM-412319

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.