@article{dennis_miller_hibbard_tappa_thunell_2021, title={Gondwanan fragments in the southern Appalachians}, volume={503}, ISSN={["0305-8719"]}, DOI={10.1144/SP503-2019-249}, abstractNote={Abstract Upper-plate and lower-plate asymmetric passive margin fragments are preserved within Carolinia, one of several terranes that rifted from Gondwana in the Furongian (late Cambrian) to form the Rheic Ocean. In the upper plate, 1–2 km of preserved rocks are middle Cambrian (Drumian, Ptychagnostus atavus zone) trilobite-bearing mudstones that lie above an angular unconformity and are the youngest stratified rocks in Carolinia. In the lower plate, 4–5 km of stratigraphy preserved in the Kings Mountain terrane are particularly interesting, because a 4 km thick Cambrian Series 2 clastic sedimentary section increasingly dominated by western Amazonian detritus lies above a Carolinian volcanic arc basement. Here, we describe for the first time the origin and setting of the youngest rocks in the Appalachians of wholly Gondwanan origin.}, journal={PANNOTIA TO PANGAEA: NEOPROTEROZOIC AND PALEOZOIC OROGENIC CYCLES IN THE CIRCUM-ATLANTIC REGION}, author={Dennis, A. J. and Miller, B. V. and Hibbard, J. P. and Tappa, E. and Thunell, R. C.}, year={2021}, pages={469–480} }
 @article{waldron_barr_park_white_hibbard_2015, title={Late Paleozoic strike-slip faults in Maritime Canada and their role in the reconfiguration of the northern Appalachian orogen}, volume={34}, ISSN={["1944-9194"]}, DOI={10.1002/2015tc003882}, abstractNote={Major late Paleozoic faults, many with documented strike‐slip motion, have dissected the Ordovician‐Devonian Appalachian orogen in the Maritime Provinces of Atlantic Canada. Activity alternated between east‐west faults (Minas trend) and NE‐SW faults (Appalachian trend). NW‐SE faults (Canso trend) were probably conjugate to Minas‐trend faults. Major dextral movement, on faults with Appalachian trend, in total between 200 and 300 km, began in the Late Devonian. This movement initiated the Maritimes Basin in a transtensional environment at a releasing bend formed around a promontory in the Laurentian margin and thinned the crust, accounting for the major subsidence of the basin. Appalachian‐trend strike slip continued in the Mississippian but was accompanied by major movement on E‐W Minas‐trend faults culminating around the Mississippian‐Pennsylvanian boundary, juxtaposing the Meguma and Avalon terranes of the Appalachians close to their present‐day configuration. However, strike slip continued during the Pennsylvanian‐Permian interval resulting in transpressional deformation that reactivated and inverted earlier extensional faults. A final major episode of transtension, mainly sinistral, occurred during the Mesozoic opening of the Atlantic Ocean. Restoration of movements on these faults, amounting to several hundred kilometers of slip, explains anomalies in the present‐day distribution of terranes amalgamated during early Paleozoic Appalachian tectonism. In the restored geometry, the Nashoba and Ellsworth terranes of Ganderia are adjacent to one another, and the Meguma terrane lies clearly outboard of Avalonia. A restored post‐Acadian paleogeography, not the present‐day geometry of the orogen, should be used as a basis for reconstructions of its earlier Paleozoic history.}, number={8}, journal={TECTONICS}, author={Waldron, John W. F. and Barr, Sandra M. and Park, Adrian F. and White, Chris E. and Hibbard, James}, year={2015}, month={Aug}, pages={1661–1684} }
 @article{hughes_hibbard_pollock_lewis_miller_2014, title={Detrital Zircon Geochronology Across the Chopawamsic Fault, Western Piedmont of North-Central Virginia: Implications for the Main Iapetan Suture in the Southern Appalachian Orogen}, volume={41}, ISSN={["0315-0941"]}, DOI={10.12789/geocanj.2014.41.052}, abstractNote={The Chopawamsic fault potentially represents the main Iapetan suture, previously unidentified in the southern extent of the Appalachian orogen.  The fault trends through the north-central portion of the western Piedmont of Virginia and separates the composite metaclastic Potomac terrane, commonly interpreted to be of Laurentian affinity, from the Chopawamsic terrane, the remains of a Middle Ordovician volcanic arc of uncertain crustal affinity.  To gain insight on the first-order orogenic significance of the Chopawamsic fault, we report the results of LA–ICP–MS U–Pb analyses of 1,289 detrital zircons from 13 metasedimentary rock samples collected from both sides of the fault.       The near exclusivity of Middle Ordovician zircon grains (ca. 470 – 460 Ma) in four sampled metasedimentary rocks of the Chopawamsic Formation likely represents the detrital recycling of syndepositional Chopawamsic volcanic rocks.  A subset of Cambrian and older grains hint at one or more additional, older sources.       Samples from the Potomac terrane include mostly Mesoproterozoic zircon grains and these results are consistent with previous interpretations that the metaclastic rocks are Laurentian-derived.  The youngest zircons (ca. 550 – 500 Ma) and the age of cross-cutting plutons indicate that at least some parts of the Potomac terrane are Late Cambrian – Early Ordovician.  The results imply temporally discrete and geographically isolated sedimentary systems during deposition of sedimentary rocks in the Chopawamsic and Potomac terranes.       Metasedimentary rocks near Storck, Virginia, previously identified as a successor basin, contain detrital zircon populations that indicate they are actually peri-Gondwanan derived metasedimentary rocks unrelated to a successor basin system; their geographic position between the Laurentian-derived Potomac terrane and the Chopawamsic terrane suggests a peri-Gondwanan affinity for the Chopawamsic arc and geographic separation of the Chopawamsic and Potomac terranes in the Middle Ordovician. Consequently, we tentatively support the hypothesis that the Chopawamsic fault system represents the main Iapetan suture in the southern Appalachian orogen.      Most detrital zircons from samples of the Arvonia successor basin crystallized in the Ordovician—Silurian or Mesoproterozoic.  These data suggest that the Arvonia basin was deposited in the latest Ordovician to Early Silurian only after the Late Ordovician accretion of the Chopawamsic arc to Laurentia.  SOMMAIRELa faille de Chopawamsic représente peut-être la principale suture japétienne, non-reconnue dans prolongement sud de l’orogène des Appalaches.  La faille traverse la portion nord du centre du piedmont ouest de Virginie et sépare le terrane métaclastique de Potomac, d’affinité laurentienne pensait-on, du terrane de Chopawamsic, vestige d’un arc volcanique de l’Ordovicien moyen d’affinité crustale incertain.  Afin de mettre en lumière la signification orogénique première de la faille de Chopawamsic, nous présentons les résultats d’analyses U-Pb par ICP–MS par AL sur 1 289 zircons détritiques provenant de 13 échantillons de roches métasédimentaires prélevés de chaque côté de la faille.     L’existence quasi-exclusive de grains de zircon de l’Ordovicien moyen (env. 470 – 460 Ma) dans quatre roches métasédimentaires de la Formation de Chopawamsic représente vraisemblablement le recyclage détritique des roches volcaniques synsédimentaires de Chopawamsic.  Un sous-ensemble de grains cambriens et plus anciens, évoque l’existence d’une ou plusieurs sources plus anciennes additionnelles.     Les échantillons du terrane de Potomac renferment principalement des grains de zircon du Mésoprotérozoïque, ce qui correspond avec les interprétations antérieures voulant que les roches métaclastiques soient d’origine laurentienne.  Les zircons les plus jeunes (env. 550 – 500 Ma) ainsi que l’âge des plutons qui recoupe l’encaissant indiquent qu’au moins certaines parties du terrane de Potomac sont de la fin du Cambrien ou du début de l’Ordovicien.  Les résultats impliquent l’existence de systèmes sédimentaires distincts au cours du temps, et isolés géographiquement durant le dépôt des roches sédimentaires dans les terranes de Chopawamsic et de Potomac.     Les roches métasédimentaires près de Storck en Virginie, jadis interprétées comme bassin successeur, renferment des populations de zircons détritiques qui indiquent qu’ils proviennent en fait de roches métasédimentaires péri-gondwaniennes sans rapport avec un système de bassin successeur; leur localisation géographique entre le terrane de Potomac issu des Laurentides et le terrane de Chopawamsic porte à penser que l’arc de Chopawamsic est d’affinité péri-gondwanienne, et que les terranes de Chopawamsic et de Potomac à l’Ordovicien moyen étaient séparés géographiquement.   En conséquence il nous semble justifié de proposer que le système de faille de Chopawamsic représente la principale suture japétienne dans le sud de l’orogène des Appalaches.     La plupart des zircons détritiques des échantillons du bassin successeur d’Arvonia ont cristallisés entre l’Ordovicien et le Silurien ou au Mésoprotérozoïque.  Ces données suggèrent que le bassin d’Arvonia s’est rempli de la fin entre l’Ordovicien et le début du Silurien, seulement après l’accrétion de l’arc de Chopawamsic à la Laurentie, à la fin de l’Ordovicien.}, journal={GEOSCIENCE CANADA}, author={Hughes, K. Stephen and Hibbard, James P. and Pollock, Jeffrey C. and Lewis, David J. and Miller, Brent V.}, year={2014}, pages={503–522} }
 @article{castonguay_staal_joyce_skulski_hibbard_2014, title={Taconic Metamorphism Preserved in the Baie Verte Peninsula, Newfoundland Appalachians: Geochronological Evidence for Ophiolite Obduction and Subduction and Exhumation of the Leading Edge of the Laurentian (Humber) Margin During Closure of the Taconic Seaway}, volume={41}, ISSN={["1911-4850"]}, DOI={10.12789/geocanj.2014.41.055}, abstractNote={The Baie Verte Peninsula, western Newfoundland Appalachians, preserves evidence for Early to Mid Ordovician closure of the Taconic seaway, which led to obduction of the Baie Verte oceanic tract (BVOT) ophiolites onto the Laurentian (Humber) margin and Taconic orogenesis. The scarcity of Taconic radiometric ages (and predominance of Silurian (Salinic) data) from the Humber margin rocks (down-going plate) has been problematic, calling into question the intensity and existence of Taconic collisional orogenesis. 40Ar/39Ar and in situ U–Pb geochronology was undertaken on metamorphosed units from the Laurentian basement (Mesoproterozoic East Pond Metamorphic Suite), from the ca. 560 Ma Birchy Complex forming the leading edge of the Humber margin, and from the ca. 490 Ma ophiolitic rocks of the BVOT (Advocate Complex) in order to address this question. Our results confirm evidence of Taconic metamorphism along the Humber margin and at the base of the ophiolites. Ages obtained from the structural base of the Advocate Complex (481–465 Ma) are interpreted to reflect the timing of accretion and internal thickening of the ophiolite, whereas data from the underlying Birchy Complex (467–461 Ma) record the underthrusting and exhumation of the leading edge of the Humber margin along a subduction channel, penecontemporaneously with final obduction of the BVOT. A concordant ca. 465 Ma zircon age and REE data obtained from retrogressed eclogite of the East Pond Metamorphic Suite suggest that the parautochthonous Humber margin was locally subducted to eclogite-facies conditions during the Taconic collision and partly exhumed to amphibolite-facies conditions prior to a strong Silurian (Salinic) tectonometamorphic overprint.SOMMAIRELa péninsule de Baie Verte dans les Appalaches de l’ouest de Terre-Neuve a conservé des indices de la fermeture du bras de mer taconique, qui a mené à l’obduction des ophiolites de la bande océanique de Baie Verte (BOBV) sur la marge laurentienne (Humber) et à l’orogénèse taconique. La rareté des âges radiométriques taconiques (et la prédominance des données siluriennes (saliniques)) provenant des roches de la marge de Humber (i.e. la plaque subductée) a été problématique, mettant en question l’intensité et l’existence de la collision orogénique taconique. De la géochronologie 40Ar/39Ar et U–Pb in situ a été réalisée sur des unités métamorphisés provenant du socle laurentien (la Suite Métamorphique d’East Pond d’âge Mésoprotérozoïque), du Complexe de Birchy daté à ca. 560 Ma formant la partie frontale de la marge de Humber, and des roches ophiolitiques de la BOBV (Complexe d’Advocate) datée à ca. 490 Ma afin de confronter ce questionnement. Nos résultats confirment les indices de métamorphisme taconique le long de la marge de Humber et à la base des ophiolites. Les âges obtenus à la base structurale du Complexe d’Advocate (481–465 Ma) sont interprétés comme reflétant la période d’accrétion et d’épaississement interne de l’ophiolite, tandis que les données du Complexe de Birchy sous-jacent (467–461 Ma) enregistrent le sous-charriage et l’exhumation de la partie frontale de la marge de Humber au sein d’un chenal de subduction, de façon pénécontemporaine à l’obduction finale de la BOBV. Un âge concordant de ca. 465 Ma d’un zircon et les données de terres rares provenant d’une éclogite rétromorphosée de la suite métamorphique d’East Pond suggèrent que la marge de Humber parautochtone a été localement subductée à des conditions du faciès éclogitique durant la collision taconique et partiellement exhumée à des conditions du faciès des amphibolites précédant la forte surimposition tectonométamorphique silurienne (salinique).}, journal={GEOSCIENCE CANADA}, author={Castonguay, Sebastien and Staal, Cees R. and Joyce, Nancy and Skulski, Thomas and Hibbard, James P.}, year={2014}, pages={459–482} }
 @article{hibbard_karabinos_2013, title={Disparate Paths in the Geologic Evolution of the Northern and Southern Appalachians: A Case for Inherited Contrasting Crustal/Lithospheric Substrates}, volume={40}, ISSN={["0315-0941"]}, DOI={10.12789/geocanj.2013.40.021}, abstractNote={Modern understanding of the tectonic evolution of the Appalachian orogen allows for recognition of most of the first-order lithotectonic elements and events of the mountain belt. Comparison of these features and events along the length of the orogen indicates that the northern and southern segments display distinct first-order differences.  Contrasts between these segments existed from the onset of the Appalachian cycle. It has been recognized that Mesoproterozoic basement rock types south of approximately Pennsylvania are different from those to the north and more recently it has been shown that basement rocks in each area display distinct Nd and Pb isotopic signatures. Also, an early, ca. 770–680 Ma, Cryogenian stage of rifting is recorded in the southern Appalachians, but is not documented in the northern part of the orogen. During the Paleozoic Appalachian cycle, the accretion of peri-Gondwanan terranes was partitioned; Carolinia and Suwannee are confined to the southern Appalachians, and Ganderia, Avalonia, and Meguma to the northern Appalachians. Consequential to this partitioning, associated magmatism and some of the attendant tectonism is asymmetrically distributed between the two segments of the orogen. The terminal Appalachian collisional event, the Carboniferous Alleghanian orogeny, is distinctly different in the two segments of the orogen. The volumes of Alleghanian magmatic rocks in the northern and southern Appalachians are distributed asymmetrically and Carboniferous tectonic styles contrast sharply between the two regions. In addition, there is a modern first-order topographic change in the foreland of the orogeny. The southern foreland is characterized by a continuous, elevated plateau, whereas north of the New York promontory, foreland topography is more varied.    Throughout the Appalachian cycle, all of these varied first-order changes occur in the vicinity of the New York promontory, suggesting that the promontory represents an enduring, fundamental boundary in the orogen. The nature and duration of differences between the northern and southern segments of the orogen indicate that this boundary was not an extrinsic ephemeral feature, such as a plate triple junction or hot spot. Rather, we suggest that an intrinsic difference in the Laurentian crustal/lithospheric(?) substrate present from the outset of the Appalachian cycle, as reflected by contrasts in the Mesoproterozoic basement in each segment, could be the root cause of these significant contrasts.SOMMAIREL’état actuel des connaissances sur l’évolution tectonique de l’orogène appalachien nous permet de reconnaître la plupart des éléments et des événements lithotectoniques de premier niveau de la chaîne de montagnes.  La comparaison de ces caractéristiques et événements tout au long de l'orogène permet de distinguer des différences  de premier ordre entre les segments nord et sud.  Des contrastes entre ces segments ont existé depuis le début des Appalaches.  Il a été reconnu que les roches de type socle du Mésoprotérozoïque à partir du sud de la Pennsylvanie environ, diffèrent de celles au nord, et plus récemment, il a été démontré que les roches de socle  dans chacun de ces segments ont des signatures isotopiques Nd et Pb distinctes.  En outre, un début de phase de distension au Cryogénien (770-680 Ma env.) est présent dans le segment sud des Appalaches, mais n'est pas documenté dans le segment nord de l'orogène.  Durant le cycle paléozoïque des Appalaches, l'accrétion des terranes péri-Gondwana a été partagé; les terranes de Carolinia et de Suwannee sont confinés au segment sud des Appalaches, alors que ceux de Ganderia, d’Avalonie, et de Meguma sont confinés au segment nord des Appalaches.  Conséquence de cette répartition, le magmatisme associé ainsi qu’une partie du diastrophisme relié sont répartis de manière asymétrique entre les deux segments de l'orogène.  La phase terminale de collision des  Appalaches, l'orogenèse Carbonifère alléghanienne, est nettement différente dans les deux segments de l'orogène.  Les volumes des roches magmatiques alléghaniennes dans les Appalaches septentrionales et méridionales sont répartis de manière asymétrique et les styles tectoniques carbonifères contrastent fortement entre ces deux régions.  En outre, on observe une différence topographique de premier ordre dans l’état actuel de l'avant-pays de l'orogenèse.  Le segment sud de l'avant-pays est caractérisé par un plateau élevé continu, alors qu’au nord du promontoire de New York, la topographie d'avant-pays est plus diversifiée.    Tout du long du cycle des Appalaches, tous ces changements variés de premier ordre existent au pourtour du promontoire de New York, ce qui permet de penser que le promontoire représente une frontière déterminante durable dans l'orogène.  La nature et la persistance de ces différences entre les segments nord et sud de l'orogène indiquent que cette limite n'était pas une caractéristique éphémère extrinsèque, comme une jonction triple de plaque ou un point chaud.  Nous suggérons plutôt qu'une différence intrinsèque dans la croûte/substrat lithosphérique(?) laurentien existait dès le début du cycle des Appalaches, comme en témoignent les contrastes dans le socle mésoprotérozoïque dans chaque segment, et pourrait être la cause de ces contrastes significatifs.}, journal={GEOSCIENCE CANADA}, author={Hibbard, James and Karabinos, Paul}, year={2013}, pages={303–317} }
 @article{staal_chew_zagorevski_mcnicoll_hibbard_skulski_castonguay_escayola_sylvester_2013, title={Evidence of Late Ediacaran Hyperextension of the Laurentian Iapetan Margin in the Birchy Complex, Baie Verte Peninsula, Northwest Newfoundland: Implications for the Opening of Iapetus, Formation of Peri-Laurentian Microcontinents and Taconic - Grampian Orogenesis}, volume={40}, ISSN={["0315-0941"]}, DOI={10.12789/geocanj.2013.40.006}, abstractNote={The Birchy Complex of the Baie Verte Peninsula, northwestern Newfoundland, comprises an assemblage of mafic schist, ultramafic rocks, and metasedimentary rocks that are structurally sandwiched between overlying ca. 490 Ma ophiolite massifs of the Baie Verte oceanic tract and underlying metasedimentary rocks of the Fleur de Lys Supergroup of the Appalachian Humber margin. Birchy Complex gabbro yielded a Late Ediacaran U–Pb zircon ID–TIMS age of 558.3 ± 0.7 Ma, whereas gabbro and an intermediate tuffaceous schist yielded LA–ICPMS concordia zircon ages of 564 ± 7.5 Ma and 556 ± 4 Ma, respectively. These ages overlap the last phase of rift-related magmatism observed along the Humber margin of the northern Appalachians (565–550 Ma). The associated ultramafic rocks were exhumed by the Late Ediacaran and shed detritus into the interleaved sedimentary rocks. Psammite in the overlying Flat Point Formation yielded a detrital zircon population typical of the Laurentian Humber margin in the northern Appalachians. Age relationships and characteristics of the Birchy Complex and adjacent Rattling Brook Group suggest that the ultramafic rocks represent slices of continental lithospheric mantle exhumed onto the seafloor shortly before or coeval with magmatic accretion of mid-ocean ridge basalt-like mafic rocks. Hence, they represent the remnants of an ocean – continent transition zone formed during hyperextension of the Humber margin prior to establishment of a mid-ocean ridge farther outboard in the Iapetus Ocean. We propose that microcontinents such as Dashwoods and the Rattling Brook Group formed as a hanging wall block and an extensional crustal allochthon, respectively, analogous to the isolation of the Briançonnais block during the opening of the Alpine Ligurian–Piemonte and Valais oceanic seaways.SOMMAIRELe complexe de Birchy de la péninsule de Baie Verte, dans le nord-ouest de Terre-Neuve, est constitué d’un assemblage de schistes mafiques, de roches ultramafiques et de métasédiments qui sont coincés entre des massifs ophiolitiques d’ascendance océanique de la Baie Verte au-dessus, et des métasédiments du Supergroupe de Fleur de Lys de la marge de Humber des Appalaches en-dessous. Le complexe de gabbro de Birchy a donné une datation U-Pb sur zircon ID-TIMS correspondant à la fin de l’Édiacarien, soit 558,3 ± 0,7 Ma, alors qu’un gabbro et un schiste tufacé intermédiaire montrent une datation LA-ICP-MS Concordia sur zircon de 564 ± 7,5 Ma et 556 ± 4 Ma, respectivement. Ces datations chevauchent la dernière phase de magmatisme de rift observée le long de la marge Humber des Appalaches du Nord (565-550 Ma). Les roches ultramafiques associées ont été exhumées vers la fin de l’Édiacarien et leurs débris ont été imbriqués dans des roches sédimentaires. Les psammites de la Formation de Flat Point susjacente ont donné une population de zircons détritiques typique de la marge laurentienne de Humber des Appalaches du Nord. Les relations chronologiques et les caractéristiques du complexe de Birchy et du groupe de Rattling Brook adjacent, permettent de penser que ces roches ultramafiques pourraient être des écailles de manteau lithosphérique continental qui auraient été exhumées sur le plancher océanique peu avant ou en même temps que l’accrétion magmatique de roches mafiques basaltiques de type dorsale médio-océanique. Par conséquent, elles seraient des vestiges d’une zone de transition océan-continent formée au cours de l’hyper-extension de la marge de Humber avant l’apparition d’une dorsale médio-océanique plus loin au large dans l’océan Iapétus. Nous proposons que des microcontinents comme de Dashwoods et du groupe de Rattling Brook ont constitués respectivement un bloc de toit et un allochtone crustal d’extension, de la même manière que le bloc Briançonnais a été isolé lors de l’ouverture des bras océaniques alpins de Ligurie-Piémont et de Valais.}, journal={GEOSCIENCE CANADA}, author={Staal, Cees R. and Chew, Dave M. and Zagorevski, Alexandre and McNicoll, Vicki and Hibbard, James and Skulski, Tom and Castonguay, Sebastien and Escayola, Monica P. and Sylvester, Paul J.}, year={2013}, pages={94–117} }
 @article{hughes_hibbard_miller_2013, title={RELATIONSHIP BETWEEN THE ELLISVILLE PLUTON AND CHOPAWAMSIC FAULT: ESTABLISHMENT OF SIGNIFICANT LATE ORDOVICIAN FAULTING IN THE APPALACHIAN PIEDMONT OF VIRGINIA}, volume={313}, ISSN={["1945-452X"]}, DOI={10.2475/06.2013.03}, abstractNote={The Chopawamsic fault is the most significant boundary in the western Piedmont of north central Virginia; it separates the metaclastic Early Ordovician or older Potomac terrane of Laurentian affinity from the dominantly metavolcanic Middle to Late Ordovician Chopawamsic terrane of unknown cratonic heritage. On regional maps, the Ellisville pluton had previously been depicted as stitching the Chopawamsic fault, although this relationship has never been documented. It has been hypothesized that the Chopawamsic fault marks the suture of the early Paleozoic Iapetus Ocean, which once separated Laurentian and Gondwanan crustal elements. Consequently, it is important to examine the stitching relationship in detail in order to place timing constraints on motion along this fault. We integrate detailed field mapping, kinematic analysis, petrography, major-oxide, trace, and rare earth element geochemistry, and U-Pb zircon geochronology in order to deduce the relationships between the Ellisville pluton, the Chopawamsic fault, and thus, the Potomac and Chopawamsic terranes in central Virginia. Our study reveals local textural and minor geochronologic variations in the Ellisville pluton, whereas composition and geochemistry are mostly homogenous throughout the body. These data, along with 1:24,000 scale mapping, collectively confirm that the Ellisville pluton stitches the Potomac and Chopawamsic terranes across the Chopawamsic fault. New U-Pb zircon geochronological analyses yield ages of ca. 444 Ma and ca. 437 Ma, and indicate that the latest significant movement of the fault occurred before a 443.7 ± 3.3 Ma main phase of magmatism present throughout the Ellisville pluton. These dates, with previously determined crystallization ages from the Chopawamsic terrane, constrain significant movement on the Chopawamsic fault to a ca. 10 million year interval in the Late Ordovician between ca. 453 to 444 Ma. Whether the accretion of the Chopawamsic terrane involved the closing of either a back-arc seaway or a global ocean has yet to be determined; however, based on its timing and kinematic nature, we suggest that the development of the Chopawamsic fault may be related to the Late Ordovician to Early Silurian Cherokee orogeny.}, number={6}, journal={AMERICAN JOURNAL OF SCIENCE}, author={Hughes, K. Stephen and Hibbard, James P. and Miller, Brent V.}, year={2013}, month={Jun}, pages={584–612} }
 @article{hibbard_miller_hames_standard_allen_lavallee_boland_2012, title={Kinematics, U-Pb geochronology, and 40Ar/39Ar thermochronology of the Gold Hill shear zone, North Carolina: The Cherokee orogeny in Carolinia, Southern Appalachians}, volume={124}, ISSN={["1943-2674"]}, DOI={10.1130/b30579.1}, abstractNote={The Gold Hill shear zone is the most prominent pre-Carboniferous structure in the Southern Appalachian peri-Gondwanan tract of Carolinia. Common perception, based on indirect evidence, holds that it is an Acadian, dextral strike-slip shear zone. However, our recent structural and geochronologic studies directed at the shear zone indicate that it is a complex structure in both time and space. Structural studies in central North Carolina kinematically link deformation in the shear zone to regional shortening structures in both the hanging wall and footwall and indicate that there was a sinistral component to the deformation. Collectively, these structures constitute a regional sinistral transpressional system. We obtained nine new U-Pb zircon ages (Ediacaran–Devonian) and 12 new 40 Ar/ 39 Ar muscovite ages (Late Ordovician–Middle Mississippian); these data, in conjunction with the regional geology indicate that the shear zone has ∼12 km of stratigraphic throw and that the main motion on the zone was Late Ordovician. Collectively, geologic relations, structures, and the distribution of 40 Ar/ 39 Ar ages indicate that the shear zone was reactivated in the Late Devonian and the Middle Mississippian. The regional Late Ordovician–Silurian sinistral transpressive system, of which the Gold Hill shear zone is part, represents the most widespread tectonism documented in Carolinia; it overlaps in time with the Ordovician–Silurian Cherokee unconformity in Laurentian strata and Late Ordovician–Silurian suprasubduction-zone magmatism and metamorphism in peri-Laurentian rocks and consequently is considered a manifestation of the Southern Appalachian Cherokee orogeny, marking the accretion of Carolinia to Laurentia.}, number={5-6}, journal={GEOLOGICAL SOCIETY OF AMERICA BULLETIN}, author={Hibbard, James P. and Miller, Brent V. and Hames, Willis E. and Standard, Issac D. and Allen, John S. and Lavallee, Sarah B. and Boland, Irene B.}, year={2012}, pages={643–656} }
 @article{pollock_hibbard_2010, title={Geochemistry and tectonic significance of the Stony Mountain gabbro, North Carolina: Implications for the Early Paleozoic evolution of Carolinia}, volume={17}, ISSN={["1342-937X"]}, DOI={10.1016/j.gr.2009.09.009}, abstractNote={Carolinia comprises a collection of Neoproterozoic–Early Paleozoic magmatic arc and sedimentary terranes that were amalgamated and accreted to Laurentia in the early to middle Paleozoic. In central North Carolina, mafic rocks of the Stony Mountain gabbro intrude sub-aqueous volcanic and sedimentary rocks and submarine epiclastic sedimentary rocks of the Albemarle Group. The age of the Stony Mountain gabbro is constrained to the Early Cambrian–Middle Ordovician. Field relations indicate that the gabbro represents the final phase of magmatism following the eruption and deposition of the Neoproterozoic–earliest Cambrian Albemarle Group, yet the gabbro pre-dates regional metamorphism and tectonism related to the Late Ordovician accretion of Carolinia to Laurentia. The Stony Mountain gabbro has a sub-alkaline basaltic composition, variable TiO2, MgO and Ni/Cr values. The rocks have a geochemical signature typical of island-arcs; the degree of LREE enrichment, prominent negative Nb anomalies and Nb/Th ratios are all features of low-K to medium-K tholeiitic basalts in modern island-arc, subduction-related lavas. Isotope data are dominated by juvenile compositions that are consistent with derivation from lithospheric and asthenospheric sources during decompression melting of the mantle. The Stony Mountain gabbro records subduction zone magmatism in a rifted island arc setting and can be modeled as the product of ~ 10–15% hydrous partial melting of variable mixtures of MORB- and OIB-like mantle sources overprinted by a minor subducted-slab derived hydrous fluid component. By analogy with modern settings the rocks of the Stony Mountain gabbro are comparable to MORB-like to OIB-type enriched rocks from the Lau Island and Sumisu Rift and are interpreted to have formed within an evolving Early Paleozoic island arc–back arc rift–basin system. The presence of an Early Cambrian arc–back arc rift system in Carolinia is broadly coeval with arc–back arc volcanism in other peri-Gondwanan blocks of the Appalachians and may be related to the Early Paleozoic opening of the Rheic Ocean.}, number={2-3}, journal={GONDWANA RESEARCH}, author={Pollock, Jeffrey C. and Hibbard, James P.}, year={2010}, month={Mar}, pages={500–515} }
 @article{pollock_hibbard_sylvester_2009, title={Early Ordovician rifting of Avalonia and birth of the Rheic Ocean: U-Pb detrital zircon constraints from Newfoundland}, volume={166}, ISSN={["0016-7649"]}, DOI={10.1144/0016-76492008-088}, abstractNote={Abstract: Avalonia is the largest accreted crustal block in the Appalachian orogen and comprises a collection of late Neoproterozoic volcano-sedimentary sequences that are overlain by a Palaeozoic platformal sedimentary succession. Detrital zircons from the Conception Group are dominated by 570–620 Ma ages and contain a significant component generated by erosion of coeval igneous arc-volcanic rocks. Overlying samples from the Cuckold and Crown Hill formations are dominated by Neoproterozoic populations with ages between 600 and 650 Ma and are interpreted to be derived from the underlying calc-alkaline arc-plutonic rocks. Early Palaeozoic platform units are dominated by c. 620 Ma zircons with lesser Mesoproterozoic and Palaeoproterozoic zircons. The range of detrital zircon ages is inconsistent with a West African provenance and suggests that Avalonia originated along the Gondwanan margin of the Amazon craton. The influx of Mesoproterozoic and Palaeoproterozoic detritus in the Avalonian platform suggests a major change in tectonic regime. The prominent change in provenance is interpreted to be related to separation of Avalonia from Gondwana during the Early Ordovician opening of the Rheic Ocean. The Redmans Formation is interpreted to represent the rift–drift transition of the Rheic Ocean, which imposes important constraints on the palaeotectonic evolution of Avalonia. Supplementary material: U–Pb isotopic data of LA-ICP-MS analysis of detrital zircons are available at http://www.geolsoc.org.uk/SUP18346.}, journal={JOURNAL OF THE GEOLOGICAL SOCIETY}, author={Pollock, Jeffrey C. and Hibbard, James P. and Sylvester, Paul J.}, year={2009}, month={May}, pages={501–515} }
 @article{hibbard_pollock_brennan_samson_secor_2009, title={Significance of New Ediacaran Fossils and U-Pb Zircon Ages from the Albemarle Group, Carolina Terrane of North Carolina}, volume={117}, ISSN={["1537-5269"]}, DOI={10.1086/600863}, abstractNote={The Albemarle Group is one of the major defining stratigraphic units of the Carolina terrane, the best‐known division of the southern Appalachian peri‐Gondwanan block of Carolinia. As such, the group is a significant factor in the correlation of Carolinia with other peri‐Gondwanan blocks both in the Appalachians and globally. The traditionally held Ediacaran age of the group has been in question for more than a decade because of a report of Late Cambrian and younger fossils from two quarries in the group. The fossil report led to a major revision of the stratigraphy and structural reinterpretation of the Carolina terrane. Our recent studies have focused on the stratigraphy, paleontology, and geochronology of the Cid Formation in the vicinity of one of the reported Paleozoic fossil locales. Contrary to the structural reinterpretation of the Albemarle Group, Cid mudstone is shown to be in conformable and gradational contact with Flat Swamp felsic volcanics of the Cid Formation; we have obtained a precise U‐Pb zircon age of 
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 @article{hibbard_waldron_2009, title={Truncation and translation of Appalachian promontories: Mid-Paleozoic strike-slip tectonics and basin initiation}, volume={37}, ISSN={["0091-7613"]}, DOI={10.1130/g25614a.1}, abstractNote={Accreted terranes of the Appalachian Iapetan and peri-Gondwanan realms display structural trends that are mainly concordant with promontories and embayments in the Laurentian margin, indicating that during accretion, the shape of the continental margin acted as a template around which accreted terranes were molded. In North Carolina and New-foundland, post-accretion transcurrent motion appears to be recorded by displaced outboard portions of promontories, no longer concordant with those in Laurentia. A bend in structural trends confined to the peri-Gondwanan realm at the North Carolina–South Carolina state line is interpreted to represent the dextrally displaced outboard portion of the Virginia promontory. In Newfoundland, the Hermitage flexure is interpreted as a dextrally displaced Laurentian promontory that originated along strike to the northeast. In both places, promontories were truncated and dextrally translated for ~220–250 km by a Devonian–Mississippian orogen-parallel transcurrent system, which may well have extended for the length of the eastern Laurentian margin. South of the nearby St. Lawrence promontory, extreme thinning of Appalachian crust beneath the Maritimes Basin is consistent with extension at a releasing stepover. Estimates of extension are consistent with those obtained from promontory offsets.}, number={6}, journal={GEOLOGY}, author={Hibbard, James and Waldron, John W. F.}, year={2009}, month={Jun}, pages={487–490} }
 @misc{hibbard_van staal_rankin_2007, title={A comparative analysis of pre-Silurlan crustal building blocks of the northern and the southern Appalachian orogen}, volume={307}, ISSN={["1945-452X"]}, DOI={10.2475/01.2007.02}, abstractNote={The New York promontory serves as the divide between the northern and southern segments of the Appalachian orogen. Antiquated subdivisions, distinct for each segment, implied that they had lithotectonic histories that were independent of each other. Using new lithotectonic subdivisions we compare first order features of the pre-Silurian orogenic ’building blocks’ in order to test the validity of the implication of independent lithotectonic histories for the two segments. Three lithotectonic divisions, termed here the Laurentian, Iapetan, and the peri-Gondwanan realms, characterize the entire orogen. The Laurentian realm, composed of native North American rocks, is remarkably uniform for the length of the orogen. It records the multistage Neoproterozoic-early Paleozoic rift-drift history of the Appalachian passive margin, formation of a Taconic Seaway, and the ultimate demise of both in the Middle Ordovician. The Iapetan realm encompasses mainly oceanic and magmatic arc tracts that once lay within the Iapetus Ocean, between Laurentia and Gondwana. In the northern segment, the realm is divisible on the basis of stratigraphy and faunal provinciality into peri-Laurentian and peri-Gondwanan tracts that were amalgamated in the Late Ordovician. South of New York, stratigraphic and faunal controls decrease markedly; rock associations are not inconsistent with those of the northern Appalachians, although second-order differences exist. Exposed exotic crustal blocks of the peri-Gondwanan realm include Ganderia, Avalonia, and Meguma in the north, and Carolinia in the south. Carolinia most closely resembles Ganderia, both in early evolution and Late Ordovician-Silurian docking to Laurentia. Our comparison indicates that, to a first order, the pre-Silurian Appalachian orogen developed uniformly, starting with complex rifting and a subsequent drift phase to form the Appalachian margin, followed by the consolidation of Iapetan components and ending with accretion of the peri-Gonwanan Ganderia and Carolinia. This deduction implies that any first-order differences between northern and southern segments post-date Late Ordovician consolidation of a large portion of the orogen.}, number={1}, journal={AMERICAN JOURNAL OF SCIENCE}, author={Hibbard, James P. and Van Staal, Cees R. and Rankin, Douglas W.}, year={2007}, month={Jan}, pages={23–45} }
 @article{carter_hibbard_tubrett_sylvester_2006, title={Detrital zircon geochronology of the Smith River Allochthon and Lynchburg Group, southern Appalachians: Implications for Neoproterozoic-Early Cambrian paleogeography}, volume={147}, ISSN={["1872-7433"]}, DOI={10.1016/j.precamres.2006.01.024}, abstractNote={A detrital zircon geochronological study was undertaken to provide insight into the Neoproterozoic-Early Cambrian paleo-continental affinity of the Smith River Allochthon (SRA). The SRA has been depicted by some authors to represent a distal facies equivalent of the Lynchburg Group, a rift-related sequence that originated along the Laurentian margin during the Neoproterozoic-Early Cambrian opening of the Iapetus Ocean. Other workers, however, have interpreted the SRA as being exotic with respect to Laurentia and possibly of Gondwanan origin. The most predominant detrital age population in both terranes ranges from 0.9 to 1.25 Ga. Both terranes also contain minor populations ranging from 0.75 to 0.9 Ga and 1.3 to 1.4 Ga. The SRA also contains a minor population ranging from 1.4 to 1.5 Ga. The youngest detrital zircon ages in both terranes are <900 Ma. Uranium (U) concentrations in the zircons were also determined. The U concentration versus age plot of the SRA samples is similar to that of the Lynchburg Group. The majority of the grains in both terranes contain less than 500 ppm U, with the Lynchburg Group zircons containing a higher mean U concentration than the SRA (307 ppm versus 226 ppm). The striking similarities of the detrital zircon age and chemical data for the SRA and Lynchburg Group samples suggest that the SRA and Lynchburg Group share a common provenance along the Laurentian margin. These data conflict with electron microprobe (EPMA) monazite geochronological data that document an Early Cambrian tectonothermal event in the SRA. The eastern Laurentian margin was in the rift-to-drift transition by the Early Cambrian, so a tectonothermal event along the Laurentian margin at this time is difficult to envision. Based on the striking similarities of the detrital zircon data, we suggest that the SRA is most likely a distal facies equivalent of the Lynchburg Group, and thus of Laurentian origin, even though it records an Early Cambrian tectonothermal event. This interpretation is consistent with some interpretations of peri-Laurentian affinity for other terranes in the Piedmont zone of the southern Appalachians.}, number={3-4}, journal={PRECAMBRIAN RESEARCH}, author={Carter, Brad T. and Hibbard, James P. and Tubrett, Mike and Sylvester, Paul}, year={2006}, month={Jul}, pages={279–304} }
 @article{hibbard_tracy_henika_2003, title={Smith River allochthon: A southern Appalachian peri-Gondwanan terrane emplaced directly on Laurentia?}, volume={31}, ISSN={["0091-7613"]}, DOI={10.1130/0091-7613(2003)031<0215:sraasa>2.0.co;2}, abstractNote={The Smith River allochthon is in a southern Appalachian belt of metaclastic rocks that has traditionally been considered to be of peri-Laurentian origin. New Th-U-Pb monazite ages confirm that the allochthon was involved in an Early Cambrian tectonothermal event, indicate that it was exotic with respect to adjacent Laurentian rocks, and indicate that it is likely of Gondwanan origin. The allochthon may form a new link between the Appalachians and the Pampean terrane of western South America; in addition, its position in the orogen has implications for recent models of the opening of the Iapetus.}, number={3}, journal={GEOLOGY}, author={Hibbard, JP and Tracy, RJ and Henika, WS}, year={2003}, month={Mar}, pages={215–218} }
 @misc{hibbard_stoddard_secor_dennis_2002, title={The Carolina Zone: overview of Neoproterozoic to Early Paleozoic peri-Gondwanan terranes along the eastern flank of the southern Appalachians}, volume={57}, ISSN={["1872-6828"]}, DOI={10.1016/S0012-8252(01)00079-4}, abstractNote={The Carolina Zone is an amalgamation of mainly Neoproterozoic–Early Paleozoic metaigneous-dominated terranes that are clustered along the eastern flank of the southern Appalachians. These terranes are distinguished from other divisions of the orogen by a commonality in gross geologic content and by their close spatial association. They are considered exotic relative to Laurentia on the basis of stratigraphic and tectonic evolution, paleontology, and position in the orogen analogous to that of exotic terranes in the northern Appalachians. They are probably peri-Gondwanan in origin. Within this first-order identity, the terranes exhibit remarkable heterogeneity, with respect to deposition, magmatism, and tectonothermal overprint. The depositional–magmatic history of the zone is viewed in three broad stages, including: (I) pre-600 Ma, (II) ca. 590–560 Ma, and (III) younger than ca. 550 Ma. Although each stage records significant felsic volcanism, there are few compelling stratigraphic linkages between terranes. Stage III plutonism may form a link between the two largest terranes in the zone. The isotopic evolution of the zone reflects the stratigraphic heterogeneity; isotopically juvenile magmatism in some terranes is coeval with more crustally evolved magmatism in others. The tectonothermal history of the zone is heterogeneous, producing a patchwork of suprastructural and infrastructural elements of different ages. Major tectonothermal events responsible for this pattern span the Neoproterozoic–earliest Cambrian, the Late Ordovician–Silurian, and the late Paleozoic. Evidence for regionally extensive events in the zone is sparse and such a fundamental concept as its time of accretion to Laurentia is speculative. The central Piedmont shear zone, a late Paleozoic ductile thrust that defines the western limit of the Carolina Zone, marks the final emplacement of the zone against Laurentian elements.}, number={3-4}, journal={EARTH-SCIENCE REVIEWS}, author={Hibbard, JP and Stoddard, EF and Secor, DT and Dennis, AJ}, year={2002}, month={May}, pages={299–339} }
 @article{hibbard_2000, title={Docking Carolina: Mid-Paleozoic accretion in the southern Appalachians}, volume={28}, ISSN={["0091-7613"]}, DOI={10.1130/0091-7613(2000)28<127:dcmait>2.0.co;2}, abstractNote={Accretion of the extensive Carolina zone to Laurentia is one of the most critical unresolved problems in southern Appalachian tectonics. Synthesis of southern Appalachian tectonism reveals three lines of evidence from across the orogen that indicate a Late Ordovician to Silurian time of accretion. A tectonic unconformity in native Laurentian rocks, an extensive magmatic pulse in the Piedmont zone of the orogen, and active uplift in the Carolina zone are all related to this accretionary event. Structural geometries in the Carolina zone suggest that accretion involved sinistral transpression. This new model for Carolina accretion is consistent with models for the accretion of northern Appalachian peri-Gondwanan terranes; collectively their timing and mode of accretion to Laurentia place tectonic constraints on Paleozoic global reconstructions.}, number={2}, journal={GEOLOGY}, author={Hibbard, J}, year={2000}, month={Feb}, pages={127–130} }
 @article{wortman_samson_hibbard_1998, title={Precise timing, constraints on the kinematic development of the Hyco shear zone: Implications for the central Piedmont shear zone, southern Appalachian orogen}, volume={298}, ISSN={["0002-9599"]}, DOI={10.2475/ajs.298.2.108}, abstractNote={The recently discovered Hyco shear zone is a major tectonic boundary that separates terranes (Milton and Carolina) with sharply contrasting rock types, structural and metamorphic histories, and Nd isotopic compositions. Precise U-Pb zircon dates for an orthogneiss, a granitic gneiss, and synkinematic granites within the Hyco shear zone constrain the timing of motion, deformation, and metamorphism along this fundamental southern Appalachian structure. The synkinematic Yanceyville granite gneiss yields an upper intercept date of 335.4+ or -2.2 Ma. The syn-to late-synkinematic Kilgore granite crystallized at 327+ or -1.5 Ma. A Neoproterozoic hornblende gneiss from the northern portion of the zone yields a lower intercept date of 322.5+ or -2.7 Ma, which is interpreted to reflect the timing of deformation and metamorphism. The crystallization age of the Farmers Lake granite, a late-synkinematic intrusion, is 319.6+ or -0.7 Ma. These new dates document that the Hyco shear zone was active by mid-Mississippian time and that deformation and metamorphism were in their final stages by latest Mississippian time. The Hyco shear zone is considered the northernmost segment thus far recognized of the central Piedmont shear zone, an orogen-scale structure within the southern Appalachians that separates rocks of uncertain crustal affinity in the Piedmont zone from exotic, arc-related rocks of the Carolina zone. Comparison of the kinematic history of the Hyco shear zone with kinematic histories of more southerly segments of the central Piedmont shear zone indicates that Alleghanian deformation and metamorphism probably occurred contemporaneously along the entire shear zone. These observations are permissive of a model for the central Piedmont shear zone as an Alleghanian ductile shear zone that may extend from Georgia into the central Appalachians.}, number={2}, journal={AMERICAN JOURNAL OF SCIENCE}, author={Wortman, GL and Samson, SD and Hibbard, JP}, year={1998}, month={Feb}, pages={108–130} }
 @article{vines_hibbard_shell_1998, title={Structural geology of the High Rock granite: Implications for displacement along the Hyco Shear zone, North Carolina}, volume={37}, number={4}, journal={Southeastern Geology}, author={Vines, J. A. and Hibbard, J. P. and Shell, G. S.}, year={1998}, pages={163-} }
 @article{hibbard_shell_bradley_samson_wortman_1998, title={The Hyco shear zone in North Carolina and southern Virginia: Implications for the Piedmont zone Carolina zone boundary in the southern Appalachians}, volume={298}, ISSN={["0002-9599"]}, DOI={10.2475/ajs.298.2.85}, abstractNote={The recently recognized Hyco shear zone is a first-order structure in the southern Appalachians that separates sharply contrasting rocks of the Carolina and Milton terranes in north central North Carolina and southern Virginia. Traditionally, this boundary has been viewed as a comformable contact between infrastructural Milton rocks and suprastructural Carolina rocks. In contrast, our work indicates that shallowly dipping, sillimanite gneisses of the Milton terrane comprise the footwall of the ductile shear zone whereas moderately to steeply-dipping greenschist to amphibolite facies Carolina terrane gneisses and metavolcanics form the hangingwall. The Hyco shear zone has a sharply arcuate surface trace: it trends east-northeast in the area of Hyco Lake, North Carolina, and abruptly changes trend to north-northeast near the North Carolina-Virginia state line. The zone is moderately to steeply south-southeast-dipping along the Hyco Lake segment, and structures there indicate dominantly dextral strike slip. Along the Virginia segment, the zone is moderately to shallowly east-dipping, with structures indicating thrusting of the Carolina terrane over the Milton terrane. Timing constraints on synkinematic plutons indicate that the shear zone is an early Alleghanian feature. The geometry, kinematics, and timing of the shear zone are compatible with the interpretation that the Hyco Lake and Virginia segments of the zone represent lateral and frontal ramps, respectively, in an overall Alleghanian thrust regime. Recognition of the shear zone in conjunction with geological, geophysical, and isotopic contrasts across the zone negates established views that the Milton rocks are a comformable, higher grade portion of the Carolina terrane. These contrasting features, instead, are remarkably similar to those found along the central Piedmont suture, the tectonic boundary between the Piedmont and Carolina zones from South Carolina to central North Carolina. We propose that the Hyco shear zone is the northern equivalent of this structure; thus, our new data on the Hyco shear zone have significant regional implications concerning the nature, timing, and kinematics of this zone boundary.}, number={2}, journal={AMERICAN JOURNAL OF SCIENCE}, author={Hibbard, JP and Shell, GS and Bradley, PJ and Samson, SD and Wortman, GL}, year={1998}, month={Feb}, pages={85–107} }