[Eoas-seminar] Geology Dissertation Defense - Mary Beth Lupo - June 23, 11:00am - Zoom

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Wed Jun 9 14:24:08 EDT 2021

Geology Dissertation Defense - Mary Beth Lupo - June 23, 11:00am
Major Professor: Jim Tull
Topic: M. Lupo Dissertation Defense
Time: Jun 23, 2021 11:00 AM Eastern Time (US and Canada)

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Meeting ID: 688 452 7658
Passcode: Epperson
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Meeting ID: 688 452 7658
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The Epperson synclinorium contains a key sequence of Middle Paleozoic stratigraphy nested within the main mass of the western Blue Ridge-Talladega belt allochthon. For many decades, previous interpretations have assigned these rocks to the Neoproterozoic Wilhite Formation of the Ocoee Supergroup. Fossils from the newly defined Jacks River Formation (formerly Wilhite Formation) provide a revised Silurian-Devonian age assignment to this sequence. The Epperson synclinorium is characterized as a tight to isoclinal, doubly-plunging northwest-overturned, first-order, first-generation fold. It is regionally extensive, spanning >80 km along strike and >11 km across strike, and is considered to be the westernmost complimentary structure to the Copperhill anticlinorium and Murphy synclinorium (west to east respectively). It's western upright limb is mostly structurally removed, as is most of its southern nose, by both the Great Smoky and Alaculsy Valley-Sylco Creek-Miller Cove thrust faults. Within the synclinorium, a regional low-angle unconformity separates Neoproterozoic-Lower Cambrian rift-drift sediments from the nested Middle Paleozoic successor basin sequence (Jacks River Formation). The relationship between the S1 surfaces and F1 folds, their axial planar orientations and pervasiveness suggest that regional metamorphism occurred concurrently with this first-generation fold event.
This allochthon also contains two other successor basin sequences 1) the Lay Dam Formation (Talladega Group, western Blue Ridge-Talladega belt extension) and 2) the Mineral Bluff Group (Murphy synclinorium). Both of these sequences exhibit similar stratigraphic and structural relationships with the respective underlying Lower Cambrian - Lower Ordovician and/or Neoproterozoic units, and are bounded below by low-angle unconformities. A fourth structurally isolated and stratigraphically unconstrained Middle Paleozoic successor basin sequence known as the Maggies Mill Formation is recognized in the neighboring Maggies Mill and Citico thrust sheets. Regional correlations are made possible through a variety of key lithologic indicators and paleontologic recoveries, including: A) distinct lithofacies, including carbonate olistoliths, carbonate breccias containing granite clasts, and both rhythmite and calcareous metaturbidite facies, B) three of these sequences occur within the main mass of western Blue Ridge-Talladega belt stratigraphy and therefore a continuity of both the pre-successor basin and successor basin stratigraphy can be traced across the Copperhill anticlinorium and Cartersville transverse zone, and C) Silurian-Devonian conodont elements and molds recovered from three of the four sequences and a post-Cambrian pelmatozoan echinoderm column in the fourth.
Regionally, a single set of Barrovian metamorphic isograds are mapped continuously across the western Blue Ridge-Talladega belt. These isograds are prograde from the lower greenschist rocks in the Epperson synclinorium to upper amphibolite facies rocks flanking the Murphy synclinorium and are believed to represent a single metamorphic event. The same biotite and garnet isograds mapped along the eastern overturned limb of the Epperson synclinorium and western overturned limb of the Copperhill anticlinorium are present in the Talladega belt. A structural synthesis of the region including finite strain studies cited from previous workers, F1/S1 observations reported here and again by others cited in the text, coupled with regional stratigraphic correlations of stratigraphy both above and below a regionally extensive (?) low-angle unconformity and their Middle Paleozoic assignments, demonstrate that the metamorphism recorded in these rocks must post date Ordovician Taconic-age metamorphism and instead likely record an Alleghanian metamorphic event.
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