1 Spanning an Orogen–From the Scandinavian Caledonides of Norway to the Southernmost Appalachians of Alabama I: In Honor of the Career of James F. Tull

Monday, 15 April 2024
8:00 AM - 12:00 PM
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MIDDLE PALEOZOIC SUCCESSOR BASIN SEQUENCES IN THE SOUTHERN APPALACHIAN WESTERN BLUE RIDGE/TALLADEGA BELT: CELEBRATING DECADES OF WORK AND IMPLICATIONS FOR TECTONIC EVOLUTION

Paper number: 1-10
Program: Symposia Sessions
Time: 10:45 AM – 11:05 AM

Authors

  • Mary Lupo Presenting Author
    Florida Geological Survey, Tallahassee, FL
  • Mary Lupo Presenting Author
    Florida State University, Tallahassee, FL
  • James F. Tull
    Florida State University, Tallahassee, FL

Abstract

The s. Appalachian western Blue Ridge/Talladega belt (WBRTB) is a composite metamorphic allochthon located at the junction of GA, NC, & TN and continuing SW into AL. The WBRTB consists of three major thrust sheets containing four structurally isolated, middle Paleozoic successor basin sequences (SBS). These include: 1) the Maggies Mill Fm. (MMF), isolated as fault horses in the Maggies Mill-Citico thrust sheet with no accompanying stratigraphic constraints, 2) the structurally overlying Jacks River Fm. (JRF), nested in the core of the Epperson synclinorium (ES), 3) the Mineral Bluff Gp. (MBG), nested in the core of the Murphy synclinorium (MS) and located SE of the ES and Copperhill anticlinorium (CA), & 4) the Talladega Gp. (TG), the SW extension of the WBRTB. Each SBS is dominated by a distinct sequence of rhythmites and/or calcareous metaturbidites, locally containing olistostromes and polymictic carbonate breccias containing granitic basement clasts. The JRF, MBG, & TG all occur within the main mass of the WBRTB above the Miller Cove fault. The base of each sequence is marked by a regionally extensive low-angle unconformity that steps across underlying units (L. Cambrian to Neoproterozic). Fossil assemblages in the TG, JRF, & MMF SBS constrain their depositional ages to only as old as Silurian-Devonian. The fourth (MBG) is paleontologically dated as post-Cambrian, but structural and stratigraphic relationships confirm a relationship with the along strike TG, and the JRF to the NW across the CA. Furthermore, U-Pb zircon analyses reveal a Silurian crystallization age for the Marble Hill Hornblende Schist, at the base of the MBG. The ES, CA, & MS are large scale, F1, NW overturned, tight to isoclinal folds that formed contemporaneously with peak metamorphism (greenschist to upper amphibolite facies) and contain a pervasive regional axial planar cleavage. Finite strain studies above and below the unconformity indicate that all units experienced a very similar strain history. The region is marked by a single set of regional metamorphic isograds which overprint the SBS. The regional metamorphic, structural, and stratigraphic relationships; and unique biostratigraphic constraints characterizing these successor basin sequences suggest a revised tectonic model detailing the evolution of these post-Taconic sequences.

Geological Society of America Abstracts with Programs. Vol. 56, No. 2

doi: 10.1130/abs/2024SE-398092

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