Distinct groupings of late Neoproterozoic tectonomagmatic and depositional events at 760 Ma, 685-670 Ma, 635-590 Ma and 590-545 Ma are recognized within the peri-Gondwanan margin of the Newfoundland Appalachians. This pre-Iapetan orogenic activity resulted in amalgamation of distinctive tectonic packages prior to deposition of a shale-rich platformal cover of terminal Neoproterozoic to Early Ordovician age, east of the Appalachian central mobile belt. The late Neoproterozoic successions chronicle, in part, the development of segments of a larger peri-Gondwanan orogenic system that was dispersed prior to, and variously reworked during, the protracted evolution of the southern Iapetus Ocean.The oldest orogenic events yet identified in the Newfoundland Avalonian belt occurred at and prior to 760 Ma and are manifest by the accumulation of submarine mafic volcanic rocks, the emplacement of oceanic gabbros, and the associated deposition of unique clastic and carbonate olistostromes. As early as 685 Ma, arc-related volcanic and associated arc-root plutonic complexes of felsic to intermediate composition developed along the orogenic belt in an overall contractional environment. These complexes, which are preserved together with amphibolite gneisses and associated intrusive rocks, were inhomogeneously deformed and then uplifted prior to the onset of widespread (635-590 Ma) volcanism, marine sedimentation, and coeval calc-alkaline plutonism, the products of which were deposited upon or emplaced into the 685-670 Ma basement. Locally, pre-600 Ma rocks have been inhomogeneously deformed prior to a complex volcanic, plutonic, and structural event (590-545 Ma), partly extensional and partly contractional in nature, during which the classical Ediacaranbearing and younger sedimentary successions of the Avalonian belt accumulated.Diverse tectonic elements that evolved prior to the Cambrian were variably dispersed at several times, perhaps most significantly during late Neoproterozoic orogenesis. Pronounced terminal Neoproterozoic and early Paleozoic tectonothermal events were recorded on the inboard Iapetan margin of the belt, while elsewhere, terminal Neoproterozoic through Cambro-Ordovician platformal sediments were deposited, in most cases without apparent hiatus. These contrasting peri-Gondwanan terranes were reamalgamated and again dispersed during complex transpressional orogenesis of Silurian age related to closure of the Iapetus Ocean, and ensuing collision of Gondwanan and Laurentian elements of the Appalachian orogen.

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The Grand Bruit Fault Zone of southern Newfoundland is a fundamental structure within Late Precambrian basement on the Gondwanan margin of the Appalachian orogen. Within the fault zone, a sequence of structures documents changes in the sense of ductile displacement from (1) reverse dip slip, to (2) dextral strike slip, to (3) sinistral oblique slip, and, finally, to (4) dextral lateral offsets. Fault movements along this structure were punctuated by emplacement of a variety of plutons and minor intrusions which, when precisely dated, allow these movements to be bracketed at between 571 Ma and 564 Ma, 497 Ma and 427 Ma, 424 Ma and 420 Ma, and 421 Ma and 387 Ma, respectively. The tectonic evolution of the Gondwanan inlier of southern Newfoundland is mirrored, in large part, by the record of mylonite development within the Grand Bruit Fault Zone. These tectonic events are attributable to well‐constrained, regional orogenic events of both the Pan‐African and Appalachian cycles. Newly formed shear zones in the fault zone reactivate parts of much older faults of similar regional orientation and are, in some cases, kinematically indistinguishable from the ancestral structures. Integration of precise geochronological data with the sequence of overprinted fault structures demonstrates that, although the role of progressive deformation in shear zone development was important, the observed disposition of structures and rock units is primarily a function of polyorogenic accretion. As a multiple‐reactivated structural lineament in a Gondwanan basement inlier, the fault zone exerted fundamental control over the tectonic development of the leading edge of the convergent southeast margin of the orogen.

The Sops Head Complex of Badger Bay, central Newfoundland, includes olistostromal and tectonized mélanges and marks the Red Indian Line, the boundary between the peri-Gondwanan Exploits and peri-Laurentian Notre Dame subzones of the oceanic Dunnage Zone. Basalts in the olistostromal mélange preserve peperitic contacts with mudstone and limestone within slumped sedimentary units, demonstrating that magmatism was coeval with olistostrome formation. Conodonts from the limestones date these events as late Darriwilian ("Llandeilian," Middle Ordovician) in age. The conodont fauna consists entirely of North Atlantic Faunal Realm elements, suggesting a peri-Gondwanan or mid-Iapetan provenance for limestone of the Sops Head Complex. Basalt geochemistry suggests magmatism in a mature volcanic-arc to back-arc setting. The Sops Head Complex shows similarities in age, provenance, and stratigraphic setting to the Dunnage Mélange, suggesting that the two units are correlative.

Only one specimen of a Silurian graptolite has ever been recorded from Newfoundland, and it was not identifiable below generic level. The graptolite assemblage discussed and figured here, from a sequence of turbidites on Upper Black Island, northcentral Newfoundland, includes the first positively identified Silurian taxa from the province, and provides the first unequivocal evidence of Silurian oceanic sedimentation in the Dunnage Zone. The graptolite taxa include Rastrites peregrinus (Barrande), Coronograptus? sp. cf. C. gregarius (Lapworth), Monograptus austerus sequens Hutt?, Orthograptus insectiformis (Nicholson), Monograptus spp. indet., "Climacograptus"? sp., and Glyptograptus? sp. This assemblage demonstrates that the strata, previously assigned to the Middle Ordovician Lawrence Harbour Formation, are actually Aeronian (middle Llandovery) in age and that the turbidites considerably postdate both the Lawrence Harbour and Point Leamington formations of the Exploits Subzone. Furthermore, the graptolite fauna is similar to that found in coeval sediments in the United Kingdom and Scandinavia but unlike any assemblages known from elsewhere in North America. This suggests the presence of open oceanic conditions, or deep marginal basins during the Llandovery hosting graptolites with European affinities, and raises the possibility that at least part of the Iapetus Ocean was still open in central Newfoundland during Early Silurian times. Jusqu'i prksent, un seul spCcimen de graptolite silurien a Ct C enregistrC i Terre-Neuve, et il n'a pu Ctre identifie au deli du I niveau gknerique. L'association de graptolites discutte et illustrCe ici, provenant d'une sCquence de turbidites sur I'ile Upper Black, au centre-nord de Terre-Neuve, inclut pour la premiltre fois un taxon silurien clairement identifik dans cette province, 1 et dCmontre aussi pour la premibre fois, et sans Cquivoque, la prCsence de stdiments ocCaniques siluriens dans la Zone de I Dunnage. Le taxon de graptolites inclut Rastrites peregrinus (Barrande), Coronograptus? sp. cf. C. gregarius (Lapworth), I I Monograptus austerus sequens Hutt?, Orthograptus insectifomis (Nicholson), Monograptus spp. indCt., << Climacogratus D? sp. et Glyptograptus? sp. Cette association dCmontre que les strates, assignkes anttrieurement i la Formation de Lawrence 1 Harbour d'bge ordovicien moyen, sont vkritablement d'bge aCronien (LlandovCrien moyen), et que les turbidites postdatent considCrablement les formations de Lawrence Harbour et de Point Leamington de la Sous-zone d'Exploits.En plus, cette faune de graptolites est semblable B celle trouvCe dans les sCdiments accumulCs simultanCment dans le Royaume-Uni et la Scandinavie, mais elle se distingue de toutes associations connues ailleurs en AmCrique du Nord. Ce qui suggbre la prtsence de conditions ocCaniques ouvertes, ou de bassins marginaux profonds habites par des graptolites d'affinitCs europCennes durant le Llando-

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