Confirmation of the southwest continuation of the Cat Square terrane, southern Appalachian Inner Piedmont, with implications for middle Paleozoic collisional orogenesis

Huebner, Matthew T.; Hatcher, Robert D.; Merschat, Arthur J.

doi:10.2475/02.2017.01

Cited by 13 publications

(6 citation statements)

References 63 publications

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Section: Tectonic Backgroundmentioning

confidence: 99%

“…The Inner Piedmont consists primarily of metasedimentary rocks thought to have been deposited on oceanic crust outboard of the Laurentian margin and developed into an accretionary prism ahead of the Carolina Superterrane (Huebner et al, ; Merschat & Hatcher, ). The region can be divided into a western portion of Laurentian affinity rocks and an eastern portion of Laurentian and Peri‐Gondwanan affinity rocks that accreted onto Laurentia during the Neoacadian orogeny (Huebner et al, ; Merschat & Hatcher, ). The Inner Piedmont is distinguished from the surrounding terranes by the relatively high metamorphic grade of its core (sillimanite I and II grade metamorphic rocks; Huebner et al, ) and is separated from neighboring terranes by highly sheared belts of lower grade rocks (Griffin, ).…”

Section: Tectonic Backgroundmentioning

confidence: 99%

“…The region can be divided into a western portion of Laurentian affinity rocks and an eastern portion of Laurentian and Peri‐Gondwanan affinity rocks that accreted onto Laurentia during the Neoacadian orogeny (Huebner et al, ; Merschat & Hatcher, ). The Inner Piedmont is distinguished from the surrounding terranes by the relatively high metamorphic grade of its core (sillimanite I and II grade metamorphic rocks; Huebner et al, ) and is separated from neighboring terranes by highly sheared belts of lower grade rocks (Griffin, ).…”

Section: Tectonic Backgroundmentioning

confidence: 99%

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Constraints on Appalachian Orogenesis and Continental Rifting in the Southeastern United States From Wide‐Angle Seismic Data

et al. 2019

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The Southeastern United States is an ideal location to understand the interactions between mountain building, rifting, and magmatism. Line 2 of the Suwannee suture and Georgia Rift basin refraction seismic experiment in eastern Georgia extends 420 km from the Inner Piedmont to the Georgia coast. We model crustal and upper mantle V P and upper crustal V S . The most dramatic model transition occurs at the Higgins-Zietz magnetic boundary, north of which we observe higher upper crustal V P and V S and lower V P /V S . These observations support the interpretation of the Higgins-Zietz boundary as the Alleghanian suture. North of this boundary, we observe a low-velocity zone less than 2 km thick at~5-km depth, consistent with a layer of sheared metasedimentary rocks that forms the Appalachian detachment. To the southeast, we interpret synrift sediments and decreasing crustal thickness to represent crustal thinning associated with the South Georgia Rift Basin and subsequent continental breakup. The correspondence of the northern limit of thinning with the interpreted suture location suggests that the orogenic suture zone and/or the Gondwanan crust to the south of the suture helped localize subsequent extension. Lower crustal V P and V P /V S preclude volumetrically significant mafic magmatic addition during rifting or associated with the Central Atlantic Magmatic Province. Structures formed during orogenesis and/or extension appear to influence seismicity in Georgia today; earthquakes localize along a steeply dipping zone that coincides with the northern edge of the South Georgia Basin and the change in upper crustal velocities at the Higgins-Zietz boundary.

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Section: Tectonic Backgroundmentioning

confidence: 99%

Section: Tectonic Backgroundmentioning

confidence: 99%

Section: Tectonic Backgroundmentioning

confidence: 99%

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Constraints on Appalachian Orogenesis and Continental Rifting in the Southeastern United States From Wide‐Angle Seismic Data

et al. 2019

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“…Regional deformation in the eastern Blue Ridge and Inner Piedmont is characterized by shallowly to moderately dipping, NE-SW-oriented foliations, and shallowly plunging, NE-SW-trending lineations (e.g., Merschat et al, 2005;Huebner et al, 2017). Major NE-SW-striking, SE-dipping faults active during the Neoacadian event include the Hollins Line, Brevard, and Chattahoochee faults.…”

Section: Geological Settingmentioning

confidence: 99%

Linking metamorphism, magma generation, and synorogenic sedimentation to crustal thickening during Southern Appalachian mountain building, USA

et al. 2019

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The nature of metamorphism, magma compositions, the spatial distribution of plutons, and foreland sediments reflect, in part, the character and thickness of continental crust. We utilized metamorphic pressure-temperature-time (P-T-t) paths, garnet Sm-Nd ages, zircon U-Pb ages, and pluton compositions to estimate paleocrustal thickness and temporal changes in crustal magma sources in the Blue Ridge of the southernmost Appalachians. Garnet Sm-Nd ages for amphibolite-facies metamorphic rocks range from 331 ± 4 to 320 ± 3 Ma. Low- and high-Sr/Y plutons that intruded these metamorphic rocks have zircon U-Pb ages of 390 ± 1 to 365 ± 1 Ma and 349 ± 2 to 335 ± 1 Ma, respectively. Therefore, garnet growth began during regional metamorphism synchronous with or shortly after intrusion of the youngest high-Sr/Y trondhjemite plutons. Phase diagram sections and thermobarometry indicate that garnet growth initiated at ∼5.8 kbar and 540 °C and grew during temperature increases of 60–100 °C and pressure increases of 2–3 kbar. The older, low-Sr/Y magmas are inferred to have been sourced in the crust at depths <∼30 km, insufficient for garnet to be stable. However, the younger, high-Sr/Y magmas are inferred to have been sourced at >30 km depths where garnet was stable. Hafnium isotopic compositions for all the plutons, but one, exhibit a range from negative initial εHf(i) to weakly positive initial εHf(i), indicating incomplete mixing of dominantly crustal sources. Our data require minimum crustal thicknesses of ∼33 km at 331 Ma; however, Alleghanian crustal thicknesses must have locally reached 39 km, based on crustal reconstruction adding the Alleghanian thrust sheet beneath the eastern Blue Ridge. We infer the presence of hot, tectonically thickened crust during intrusion of the early Alleghanian high-Sr/Y plutons and conclude that garnet growth and plutonism reflect a progressive increase in crustal thickness and depth of magma generation. The crustal thickening was synchronous with deposition of Mississippian to early Pennsylvanian sediments in the foreland basin of the Appalachian orogen between 350 and 320 Ma. This crustal thickening may have preceded emplacement of the Alleghanian thrust sheets onto the North American craton.

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“…1) (Whitmeyer and Karlstrom, 2007). Subsequent to Iapetan rifting but prior to the formation of Pangea, the southeastern Laurentian margin (current orientation) was subjected to a sequence of accretionary events resulting in the addition of the Inner Piedmont and Carolina terranes (also known as Carolinia) (Hibbard, 2000;Miller et al, 2006;Anderson and Moecher, 2009;Huebner et al, 2017). The exact number of accreted terranes and associated orogenic events is still debated (Hibbard et al, 2002;Hatcher et al, 2007;Hatcher, 2010;Hibbard et al, 2010), as are the locations of some of the terrane boundaries and vergence directions of associated subduction zones (Merschat and Hatcher, 2007;Anderson and Moecher, 2009).…”

Section: Introductionmentioning

confidence: 99%

The relative roles of inheritance and long-term passive margin lithospheric evolution on the modern structure and tectonic activity in the southeastern United States

et al. 2018

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We perform inversions for the shear-wave velocity structure of the southeastern United States (SEUS) using Rayleigh-wave phase and amplitude data from the broadband stations of the South Eastern Suture of the Appalachian Margin Experiment (SESAME) and EarthScope Transportable Array (TA). Our tomographic images of shear-wave velocities in the upper mantle beneath the SEUS provide new constraints on the evolution of mantle lithosphere, both from the inheritance of structures from repeated Wilson cycles and from processes that have occurred while at a passive margin setting. Our images also allow us to correlate these structures to evidence of Eocene to recent tectonism observed at the surface. We find evidence for both inherited structures and more recently evolved structures, both of which bear some correlation to observations of ongoing tectonism. Our results suggest that lithospheric mantle continues to evolve while in a passive margin setting and that even relatively "stable" continental mantle lithosphere is subject to episodes of delamination, foundering, and erosion due to processes that are still not well under stood. Our results provide structural constraints on the types of processes that may be ongoing and on possible explanations for the numerous observations of comparatively recent tectonic activity occurring along this passive margin setting. Tectonic History The geologic history of our study area begins with the formation of Rodinia, the supercontinent that juxtaposed the Granite Rhyolite Province of the Laurentian basement against cratons found in present-day South America, Africa, GEOSPHERE

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Confirmation of the southwest continuation of the Cat Square terrane, southern Appalachian Inner Piedmont, with implications for middle Paleozoic collisional orogenesis

Cited by 13 publications

References 63 publications

Constraints on Appalachian Orogenesis and Continental Rifting in the Southeastern United States From Wide‐Angle Seismic Data

Constraints on Appalachian Orogenesis and Continental Rifting in the Southeastern United States From Wide‐Angle Seismic Data

Linking metamorphism, magma generation, and synorogenic sedimentation to crustal thickening during Southern Appalachian mountain building, USA

The relative roles of inheritance and long-term passive margin lithospheric evolution on the modern structure and tectonic activity in the southeastern United States

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