NORTH AMERICA/Northern Appalachians 81 Bartholomew MJ (eds.) Geological Society of America Memoir 197, pp 459 475 Boulder, CO: Geological Society of America Faill RT (1998) A geologic history of the north central Ap palachians Part 1: Orogenesis from the Mesoproterozoic through the Taconic orogeny; Part 2: The Appalachian basin from the Silurian through the Carboniferous American Journal of Science 297: 551 569, 729 761 Faill RT (1998) A geologic history of the north central Appalachians Part 3: The Alleghany orogeny American Journal of Science 298: 131 179 Hatcher RD Jr (2001) Rheological partitioning during mul tiple reactivation of the Paleozoic Brevard Fault Zone, Southern Appalachians, USA In: Holdsworth RE, Strachan RA, Macloughlin JF, and Knipe RJ (eds.) The Nature and Significance of Fault Zone Weakening: Geological Society of London Special Publication 186, pp 255 269 London: Geological Society of London Hatcher RD Jr (2002) The Alleghanian (Appalachian) orogeny, a product of zipper tectonics: rotational transpressive continent continent collision and closing of ancient oceans along irregular margins In: Catala´n JRM, Hatcher RD Jr, Arenas R, and Garcı´a FD (eds.) Variscan Appalachian dynamics: The Building of the Late Paleozoic Basement: Geological Society of America Special Paper 394, pp 199 208 Boulder, CO: Geological Society of America Hatcher RD Jr, Thomas WA, and Viele GW (eds.) (1989) The Appalachian Ouachita orogen in the United States: The Geology of North America, vol F Boulder, CO: Geological Society of America Hibbard JP, Stoddard EF, Secor DT Jr, and Dennis AJ (2002) The Carolina zone: overview of Neoproterozoic to early Paleozoic peri Gondwanan terranes along the eastern flank of the southern Appalachians Earth Science Reviews 57: 299 339 Thomas WA, Becker TP, Samson SD, and Hamilton MA (2004) Detrital zircon evidence of a recycled orogenic foreland provenance for Alleghanian clastic wedge sand stones Journal of Geology 112: 23 37 Northern Appalachians C R van Staal, Geological Survey of Canada, Ottawa, ON, Canada ß 2005, Elsevier Ltd All rights reserved Introduction The Appalachian Orogen is a remarkably linear, north-east-trending, Palaeozoic mountain belt that generally follows the eastern seaboard of North America, with the segment between Long Island Sound and Newfoundland (Figure 1) being referred to as the Northern Appalachians Prior to the Mesozoic opening of the Atlantic Ocean, the Appalachians continued into the Caledonides of the British Isles and Scandinavia, forming a long linear mountain chain that was created by the closing of the Iapetus (Cambrian–Early Devonian) and Rheic (Devonian–Carboniferous) Oceans Iapetus started to open at the end of the Neoproterozoic (about 570 Ma) as a result of the final breakup of the supercontinent Rodinia, and had achieved a width of about 5000 km by the end of the Cambrian (500–490 Ma) The south-facing margin of ancient North America (Laurentia), which was then situated near the equator in a roughly east–west orientation, defined the northern limit of Iapetus The northern margin of Gondwana, a large continent centred on the south pole and comprising present-day Africa, Australia, Antarctica, India, and large parts of South America, represented the southern limit of Iapetus (Figure 2) The large Gondwanan landmass was assembled as a result of late Neoproterozoic to Early Cambrian collisions; thus the opening of Iapetus overlapped in time with the final assembly of Gondwana The Rheic Ocean opened when the Avalonian microcontinent rifted from Gondwana during the Early to Middle Ordovician The Rheic Ocean was host to several small continental terranes, including Meguma, which were accreted to Laurentia before the final Carboniferous arrival of Gondwana and the formation of the Pangaean supercontinent Tectonostratigraphical Divisions The tectonic architecture and the evolution of the distinctive rock assemblages in the Northern Appalachians are generally described within a framework of tectonostratigraphical zones and subzones The concept of zonal divisions, based on sharp contrasts in lithology, stratigraphy, fauna, structure, geophysics, plutonism, and metallogeny of Early Palaeozoic and older rocks, was first introduced more than 30 years ago by Harold Williams, following detailed studies of the well-exposed coastal sections in Newfoundland The identification of these zonal divisions throughout the Northern Appalachians implies a common geological evolution within each zone and highlights the usefulness of each in tectonic analysis From west to east, the Northern Appalachians have been divided into the Humber, Dunnage, Gander, Avalon, and Meguma zones (Figure 1) The Humber