61 D20. Structural Geology, Microstructures, and Geochronology

Sunday, 22 March 2020
1:30 PM - 5:30 PM
Lake Fairfax

PUSHING UP DAISIES: DOMAINAL ANALYSIS OF THE TRANSPRESSIONAL EASTERN RALEIGH TERRANE USING COMBINED LITHOLOGIC, STRUCTURAL, AND GEOCHRONOLOGIC DATA

Paper number: 61-5
Program: Technical Sessions
Time: 2:50 PM – 3:10 PM

Authors

Abstract

The Eastern Piedmont fault system (EPFS) is an array of dextral faults dissecting second-order domains into third-order terranes in the southern Appalachian hinterland. The infrastructural Raleigh terrane (Rt) in the NC-VA eastern Piedmont has been correlated with both the ca. 633-528 Ma peri-Gondwanan Carolinia and ca. 1100 and 385 Ma Laurentian Goochland domains. The EPFS separates the western Rt from Carolinia and Goochland along the Nutbush Creek-Lake Gordon fault zones and eastern Rt from Carolinia-affinity terranes along the Macon fault zone.

Three structural domains of metamorphic lithodemes are exposed in the eastern Rt across the Vicksboro-Afton 1:24K Quadrangles. A central domain has biotite zone lithologies, regional foliation, little to no mineral lineation, and few kinematic indicators. New U-Pb zircon analyses from this domain yield unimodal 403 Ma ages on metadacite similar to 403 Ma meta-monzodiorite and 410 Ma metadacite. The western and eastern domains have sillimanite-garnet zone lithologies, penetrative shear foliations and shallow stretch lineation, and dextral kinematic indicators. Three highly strained detrital samples east of the Lake Gordon fault zone in the western domain yield Mesoproterozoic grains and mid-to-late Paleozoic maximum depositional ages while two in the eastern domain yield Mesoproterozoic grains and Early Devonian maximum depositional ages. All domains record shallow-plunging, upright to overturned, open to tight F2 folds refolding shallow-to-steep plunging, moderately inclined to recumbent, tight to isoclinal F1 folds.

Domain differences may indicate dissimilar depths of deformation and east-directed thrusting of the eastern domain over the central domain. Individual domains may be petals formed during Alleghanian transpression and positive flower structure construction in the Rt east of the Nutbush Creek-Lake Gordon fault zones. The 300-297 Ma Rolesville-Wise batholith separates the western and central domains and may have intruded along a cryptic shear zone similar to other regional plutons. Refolding constrains timing of thrusting relative to folding and appears to expose the central domain as a window through the western and eastern domains. The eastern Rt does not appear to be a part of Carolinia but its affinity with Goochland remains equivocal.

Geological Society of America Abstracts with Programs. Vol. 52, No. 2

doi: 10.1130/abs/2020SE-345264

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