ABSTRACT The Baie Verte Line in western Newfoundland marks a suture zone between (1) an upper plate represented by suprasubduction zone oceanic crust (Baie Verte oceanic tract) and the trailing continental Notre Dame arc, with related upper-plate rocks built upon the Dashwoods terrane; and (2) a lower plate of Laurentian margin metasedimentary rocks with an adjoining ocean-continent transition zone (Birchy Complex). The Baie Verte oceanic tract formed during closure of the Taconic seaway in a forearc position and started to be obducted onto the Laurentian margin between ca. 485 and 476 Ma (early Taconic event), whereas the Birchy Complex, at the leading edge of the Laurentian margin, was subducted to maximum depths as calculated by pseudosection techniques (6.7–11.2 kbar, 315–560 °C) by ca. 467–460 Ma, during the culmination of the Taconic collision between the trailing Notre Dame arc and Laurentia, and it cooled isobarically to 9.2–10.0 kbar and 360–450 °C by 454–449 Ma (M 1 ). This collisional wedge progressively incorporated upper-plate Baie Verte oceanic tract rocks, with remnants preserved in M 1 high-pressure, low-temperature greenschist-facies rocks (4.8–8.0 kbar, 270–340 °C) recording typical low metamorphic gradients (10–14 °C/km). Subsequently, the early Taconic collisional wedge was redeformed and metamorphosed during the final stages of the Taconic cycle. We relate existing and new 40 Ar/ 39 Ar ages between 454 and 439 Ma to a late Taconic reactivation of the structurally weak suture zone. The Taconic wedge on both sides of the Baie Verte suture zone was subsequently strongly shortened (D 2 ), metamorphosed (M 2 ), and intruded by a voluminous suite of plutons during the Salinic orogenic cycle. Calculated low- to medium-pressure, low-temperature M 2 conditions in the Baie Verte oceanic tract varied at 3.0–5.0 kbar and 275–340 °C, with increased metamorphic gradients of ~17–25 °C/km during activity of the Notre Dame arc, and correlate with M 2 assemblages in the Birchy Complex. These conditions are associated with existing Salinic S 2 white mica 40 Ar/ 39 Ar ages of ca. 432 Ma in a D 2 transpressional shear zone and synkinematic intrusions of comparable age. A third metamorphic event (M 3 ) was recorded during the Devonian with calculated low-pressure, low-temperature conditions of 3.2–3.8 kbar and 315–330 °C under the highest metamorphic gradients (23–30 °C/km) and associated with Devonian–early Carboniferous isotopic ages as young as 356 ± 5 Ma. The youngest ages are related to localized extension associated with a large-scale transtensional zone, which reused parts of the Baie Verte Line suture zone. Extension culminated in the formation of a Middle to Late Devonian Neoacadian metamorphic core complex in upper- and lower-plate rocks by reactivation of Baie Verte Line tectonites formed during the Taconic and Salinic cycles. The Baie Verte Line suture zone is a collisional complex subjected to repeated, episodic structural reactivation during the Late Ordovician Taconic 3, Silurian Salinic, and Early–Late Devonian Acadian/Neoacadian orogenic cycles. Deformation appears to have been progressively localized in major fault zones associated with earlier suturing. This emphasizes the importance of existing zones of structural weakness, where reactivation took place in the hinterland during successive collision events.

Location Coachman's Harbour is located along the northwest coast of Baie Verte, on the Baie Verte Peninsula, Newfoundland (Fig. 1). The peninsula is accessible from the Trans-Canada Highway along Newfoundland 72, the Baie Verte highway. Coachman's Harbour is located at the end of a branch road leading east off the Baie Verte highway, approximately 15 mi (25 km) north of the community of Baie Verte (Fig. 1). Ophiolitic mélanges are best exposed at two coastal locali-ties on opposite sides of Coachman's Harbour, one near Flat Point and the other at the town picnic site (Fig. 2). For the locality near Flat Point, take the first left off the branch road, near the bottom of the hill leading to the harbour. Proceed for approx-imately 0.5 mi (0.8 km) to a lane that branches to the right; turn down the lane and park. The locality is immediately to the east-southeast along the coast. The picnic site locality is located at the end of the Coachman's Harbour branch road, near the southeastside of South Cove. Park approximately 1,000 ft (300 m) fromthe end of the road and proceed southeastward on foot to thepicnic site; the locality is along the Baie Verte coast, directlybelow the picnic grounds. No permission is necessary to visiteither locality.

Abstract Dashwoods is a composite peri-Laurentian terrane in Newfoundland and forms the basement to the Early Ordovician to Silurian Notre Dame arc. The southern part of Dashwoods is characterized by paragneiss that is intruded by Early Ordovician to Late Silurian plutons and affected by polyphase Taconic to Salinic deformation and high-grade metamorphism. The crystalline basement of Dashwoods is not exposed and pre-Middle Ordovician paragneiss is investigated herein to constrain the provenance of Dashwoods. SHRIMP U–Pb zircon analysis of the paragneiss yielded metamorphic rims ranging from c. 500 to 395 Ma and abundant detrital grain cores ranging from c. 1853 to 546 Ma. The presence of abundant Tonian dates differentiates Dashwoods from the adjacent Humber Margin in Newfoundland, and Hebridean and Grampian terranes in the British Isles. The detrital provenance of Dashwoods is most similar to the Baie Verte Margin in Newfoundland, and Tyrone Complex and Dalradian Supergroup in Ireland. These data suggest that Dashwoods and the Baie Verte Margin originated near the Rockall promontory and were subsequently emplaced outboard of the Humber Margin by Ordovician to Carboniferous motion along the Baie Verte–Brompton Line.