20 The Role of Geochronology in Constraining the Development of Earth’s Lithosphere: Focus on the U.S. South-Central Region, Mexico, and Beyond

Tuesday, 10 March 2020
8:00 AM - 12:00 PM
Meeting Room 202CD

TIMING OF NEOPROTEROZOIC-E. PALEOZOIC RIFTING, DRIFTING, TERRANE TRANSFER AND VOLCANISM, S. LAURENTIA (DEVILS RIVER UPLIFT, MARATHON BASIN, SOLITARIO)

Paper number: 20-3
Program: Theme Sessions
Time: 8:25 AM – 8:45 AM

Authors

Abstract

Integrated zircon U/Pb data (SHRIMP & LA ICP MS), whole-rock geochemical and isotopic data from W. Texas outcrops and cores shed light on evolution of S. Laurentia. Devils River Uplift, Marathon fold-thrust belt, and the Solitario – structural elements spanning ~400 km -- preserve evidence of Rodinia rifting, foundering of Iapetus, the separation of Cuyania from Laurentia and its accretion to Gondwana, accompanied by subduction volcanism.

RODINIA RIFTING (Cryogenian & Eocambrian)

Marathon Basin: First surface samples of Rodinia rift lavas. Cryogenian (706 Ma) basalt and trachyandesite boulders; intraplate rift geochemistry. Felsic tuff boulder (750-700 Ma) also yielded Eocambrian (580-520 Ma) zircons. Solitario: No lavas but rare Cryogenian detrital grains (798-657 Ma) in U. Cambrian- L. Ordovician sediments. Devils River Uplift: Laurentian rift block, Llano Grenvillian basement (1230 Ma), driven back onto the margin during Ouachita collision. Cryogenian (676 Ma) dominant in L€ metaigneous rocks; some Eocambrian (600-500 Ma) present as well.

IAPETUS OPENING, DRIFT PHASE (U. Cambrian-Mid-Ordovician)

Marathon Basin: Iapetus deepening, tectonic instability – extensive olistostromes (tens of meters) in L-MO sediments. Solitario: Headward erosion of drainages and NW-ward shift in provenance. In U€, mainly W. Texas Grenvillian (1281-1002, rare 988-809 Ma), with Granite-Rhyolite Province (1440-1300 Ma) and minor Cryogenian (798-657 Ma). In LO, first Yavapai-Mazatzal and Archean from NW; Wyoming Province Archean reworked into Yavapai-Mazatzal sediments; more abundant in MO. Rare Eocambrian (540-530 Ma). Devils River Uplift: L-M€ – Cryogenian (700-780 Ma) and Eocambrian (500-600 Ma) common in metaigneous and metasedimentary rocks. U€ – Llano Grenvillian dominant (1275-1094 Ma); common Granite-Rhyolite (1500-1300 Ma); no Cryogenian.

TERRANE TRANSFER & SUBDUCTION VOLCANISM (Mid-Ordovician)

In the L-MO the W. Ouachita Basin, Cuyania and W. Gondwana were in proximity at ~26°S. Cuyania was colliding with W. Gondwana at 470 Ma, fueling Famatina subduction volcanism. During peak arc activity (472-468 Ma) ash accumulated in the W. Ouachita-Cuyania Basin. U/Pb ages of magmatic zircons in the Ft. Peña Fm (Solitario, 488-469 Ma) and in Cuyania bentonites are within the same close range.

Geological Society of America Abstracts with Programs. Vol. 52, No. 1

doi: 10.1130/abs/2020SC-343824

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