Detrital zircon U-Pb geochronology of Cambrian to Triassic miogeoclinal and eugeoclinal strata of Sonora, Mexico

George E Gehrels, John H. Stewart

Research output: Contribution to journalArticle

55 Citations (Scopus)

Abstract

One hundred and eighty two individual detrital zircon grains from Cambrian through Permian miogeoclinal strata, Ordovician eugeoclinal rocks, and Triassic post-orogenic sediments in northwestern Sonora have been analyzed. During Cambrian, Devonian, Permian, and Triassic time, most zircons accumulating along this part of the Cordilleran margin were shed from 1.40-1.45 and 1.62-1.78 Ga igneous rocks that are widespread in the southwestern United States and northwestern Mexico. Zircons with ages of approximately 1.11 Ga are common in Cambrian strata and were apparently shed from granite bodies near the sample site. The sources of 225-280 Ma zircons in our Triassic sample are more problematic, as few igneous rocks of these ages are recognized in northwestern Mexico. Such sources may be present but unrecognized, or the grains could have been derived from igneous rocks of the appropriate ages to the northwest in the Mojave Desert region, to the east in Chihuahua and Coahuila, or to the south in accreted(?) arc-type terranes. Because the zircon grains in our Cambrian and Devonian to Triassic samples could have accumulated in proximity to basement rocks near their present position or in the Death Valley region of southern California, our data do not support or refute the existence of the Mojave-Sonora megashear. Ordovician strata of both miogeoclinal and eugeoclinal affinity are dominated by >1.77 Ga detrital zircons, which are considerably older than most basement rocks in the region. Zircon grains in the miogeoclinal sample were apparently derived from the Peace River arch area of northwestern Canada and transported southward by longshore currents. The eugeoclinal grains may also have come from the Peace River arch region, with southward transport by either sedimentary or tectonic processes, or they may have been shed from off-shelf slivers of continents (perhaps Antarctica?) removed from the Cordilleran margin during Neoproterozoic rifting. It is also possible that the Ordovician eugeoclinal strata are far traveled and exotic to North America.

Original languageEnglish (US)
Pages (from-to)2471-2487
Number of pages17
JournalJournal of Geophysical Research: Space Physics
Volume103
Issue numberB2
StatePublished - Feb 10 1998

Fingerprint

Geochronology
geochronology
Mexico
strata
zircon
Triassic
igneous rocks
Igneous rocks
arches
rocks
igneous rock
basements
rivers
Ordovician
margins
Death Valley (CA)
Rocks
Mojave Desert (CA)
Arches
basement rock

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography
  • Geochemistry and Petrology
  • Geophysics

Cite this

Detrital zircon U-Pb geochronology of Cambrian to Triassic miogeoclinal and eugeoclinal strata of Sonora, Mexico. / Gehrels, George E; Stewart, John H.

In: Journal of Geophysical Research: Space Physics, Vol. 103, No. B2, 10.02.1998, p. 2471-2487.

Research output: Contribution to journalArticle

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