Provenance of Upper Triassic strata in southwestern North America as suggested by isotopic analysis and chemistry of zircon crystals

Nancy R Riggs, Andrew P. Barth, Carlos M. González-León, Carl E. Jacobson, Joseph L. Wooden, Evan R. Howell, J. Douglas Walker

Research output: Chapter in Book/Report/Conference proceedingChapter

13 Citations (Scopus)

Abstract

The source of volcanic material in the Upper Triassic Chinle Formation on the Colorado Plateau has long been speculated upon, largely owing to the absence of similar-age volcanic or plutonic material cropping out closer than several hundred kilometers distant. These strata, however, together with Upper Triassic formations within El Antimonio and Barranca Group sedimentary rocks in northern Sonora, Mexico, yield important clues about the inception of Cordilleran magmatism in Triassic time. Volcanic clasts in the Sonsela Member of the Chinle Formation range in age from ca. 235 to ca. 218 Ma. Geochemistry of the volcanic clasts documents a hydrothermally altered source region for these clasts. Detrital zircons in the Sonsela Member sandstone are of similar age to the clasts, as are detrital zircons from the El Antimonio and Barranca Groups in Sonora. Most noteworthy about the Colorado Plateau Triassic zircons, however, are their Th/U ratios, which range from ̃1 to 3.5 in both clast and detrital zircons. Thorium/uranium ratios in the Sonoran zircons, in contrast, range from ̃0.4 to ̃1. These data, together with rare-earth-element geochemistry of the zircons, shed light on likely provenance. Geochemical comparisons support correlation of clasts in the Sonsela Member with Triassic plutons in the Mojave Desert in California that are of the same age. Zircons from these Triassic plutons have relatively low Th/U ratios, which correspond well with values from El Antimonio and Barranca Group sedimentary rocks, and support derivation of the strata, at least in part, from northern sources. The Sonsela Member zircons, in contrast, match Th/U values obtained from Proterozoic through Miocene volcanic, volcaniclastic, and plutonic rocks in the eastern and central Mojave Desert. Similarly, rare-earth-element compositions of zircons from Jurassic ignimbrites in the Mojave Desert, though overlapping those of zircons from Mojave Desert plutons, also closely resemble those from Sonsela Member zircons. We use these data to speculate that erosion of Triassic volcanic fi elds in the central to eastern Mojave Desert shed detritus that became incorporated into the Chinle Formation on the Colorado Plateau.

Original languageEnglish (US)
Title of host publicationSpecial Paper of the Geological Society of America
Pages13-36
Number of pages24
Volume487
DOIs
StatePublished - 2012

Publication series

NameSpecial Paper of the Geological Society of America
Volume487
ISSN (Print)00721077

Fingerprint

isotopic analysis
provenance
zircon
Triassic
crystal
clast
desert
pluton
plateau
sedimentary rock
rare earth element
North America
geochemistry
ignimbrite
plutonic rock
thorium
detritus
cropping practice
magmatism
Proterozoic

ASJC Scopus subject areas

  • Geology

Cite this

Riggs, N. R., Barth, A. P., González-León, C. M., Jacobson, C. E., Wooden, J. L., Howell, E. R., & Walker, J. D. (2012). Provenance of Upper Triassic strata in southwestern North America as suggested by isotopic analysis and chemistry of zircon crystals. In Special Paper of the Geological Society of America (Vol. 487, pp. 13-36). (Special Paper of the Geological Society of America; Vol. 487). https://doi.org/10.1130/2012.2487(02)

Provenance of Upper Triassic strata in southwestern North America as suggested by isotopic analysis and chemistry of zircon crystals. / Riggs, Nancy R; Barth, Andrew P.; González-León, Carlos M.; Jacobson, Carl E.; Wooden, Joseph L.; Howell, Evan R.; Walker, J. Douglas.

Special Paper of the Geological Society of America. Vol. 487 2012. p. 13-36 (Special Paper of the Geological Society of America; Vol. 487).

Research output: Chapter in Book/Report/Conference proceedingChapter

Riggs, NR, Barth, AP, González-León, CM, Jacobson, CE, Wooden, JL, Howell, ER & Walker, JD 2012, Provenance of Upper Triassic strata in southwestern North America as suggested by isotopic analysis and chemistry of zircon crystals. in Special Paper of the Geological Society of America. vol. 487, Special Paper of the Geological Society of America, vol. 487, pp. 13-36. https://doi.org/10.1130/2012.2487(02)
Riggs NR, Barth AP, González-León CM, Jacobson CE, Wooden JL, Howell ER et al. Provenance of Upper Triassic strata in southwestern North America as suggested by isotopic analysis and chemistry of zircon crystals. In Special Paper of the Geological Society of America. Vol. 487. 2012. p. 13-36. (Special Paper of the Geological Society of America). https://doi.org/10.1130/2012.2487(02)
Riggs, Nancy R ; Barth, Andrew P. ; González-León, Carlos M. ; Jacobson, Carl E. ; Wooden, Joseph L. ; Howell, Evan R. ; Walker, J. Douglas. / Provenance of Upper Triassic strata in southwestern North America as suggested by isotopic analysis and chemistry of zircon crystals. Special Paper of the Geological Society of America. Vol. 487 2012. pp. 13-36 (Special Paper of the Geological Society of America).
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