Terrane history of the Iapetus Ocean as preserved in the northern Appalachians and western Caledonides

Carbonate production and reef building under ferruginous seawater conditions in the Cambrian rift branches of the Avalon Zone, Newfoundland

“…The Appalachian Orogen of North America comprises scattered blocks of the early Palaeozoic Avalonian microcontinent, such as parts of south‐eastern New England, the Caledonian Highlands from New Brunswick, the Antigonish and Cobequid Highlands in Nova Scotia, southern Cape Breton Island and the Avalon Zone (south‐east Newfoundland) and surrounding islands (e.g. Van Staal et al ., 1998; Waldron et al ., 2022). The Avalon Zone is bounded to the north‐west by the Dover–Hermitage Bay Fault (DHBF; Fig.…”

“…Based on Cambrian biogeographic, palaeoclimatic, palaeomagnetic and facies arguments, Baltica and the Avalonian and AOMNA rifts were established in low to mid‐latitude, southern positions (Nance et al ., 2012; Waldron et al ., 2022; Murphy et al ., 2023). Strong Cambrian Epoch 2 trilobite‐based biogeographic links shared by the three sectors (Fletcher, 2006; Álvaro et al ., 2013b) evolved to a single Miaolingian Acado–Baltic Province (Sdzuy, 1972).…”

“…In contrast, where stretching gradients were low, the relative basement stability led to the growth of giant reef complexes as fault‐bounded blocks progressively coalesced into larger composite intra‐rift platforms (for example, Anti‐Atlas and Ossa‐Morena rift transects of the AOMNA Rift; Soulaimani et al ., 2003; Álvaro et al ., 2006; Álvaro & Debrenne, 2010; Álvaro et al ., 2013a; Pouclet et al ., 2018). Interpretation of the carbonate production and the record of climatically sensitive indicators along the margins of the subtropical to temperate Cambrian rifts that fringed West Gondwana (and probably Baltica), prior to and during the Ordovician opening of the Rheic Ocean (Van Staal et al ., 1998; Nance et al ., 2012; Waldron et al ., 2022), is essential to the improvement of existing palaeogeographical models. This paper, which complements a former report of sedimentological features from the same palaeogeographical area (Álvaro, 2021), presents: (i) an analysis and review of the sedimentary and oceanographic factors that controlled the nucleation, growth and demise of the microbial–shelly carbonate factories developed in a Cambrian rift transect preserved in the Avalon Zone of south‐east Newfoundland; (ii) an interpretation of the palaeoecological patterns and evolution within the transect, according to the redox conditions and phosphate availability; and (iii) a comparison of reefal and non‐reefal frameworks with neighbouring rift‐related and passive‐margin settings in similar low to mid‐latitudes.…”

Trace Element Characteristics of Pyrite and Arsenopyrite from the Golden Ridge Gold Deposit, New Brunswick, Canada: Implications for Ore Genesis

“…At first, the Canadian Appalachians were divided into 'tectonostratigraphic zones', i.e., Humber, Dunnage, Gander, Avalon, and Meguma, and subzones separated by major crustal-scale faults [25,26]; these initial subdivisions changed as a better understanding was obtained regarding the geological evolution of these zones that encompassed distinct tectonic elements and were separated by major faults [27][28][29]. Currently, the Humber zone refers to the remnants of Laurentia's Appalachian margin during the Cambrian and Ordovician, and the Dunnage zone groups the remaining fragments of several continental and oceanic arc terranes in the Iapetus Ocean that were subsequently accreted to Laurentia [30]. The Gander, Avalon, and Meguma zones represent peri-Gondwanan (Ganderia, Avalonia, and Meguma) provenance microcontinents also accreted to Laurentia [31][32][33][34].…”

Unconformity-bounded rift sequences in Terreneuvian–Miaolingian strata of the Caledonian Highlands, Atlantic Canada: Reply

“…Together with the presence of carbonate strata in the Caledonian Highlands and more broadly in the Avalon Zone, and the presence of Terreneuvian-Cambrian Epoch 2 reefs and mud-mounds in western Avalonia (see descriptions in Landing et al, 2017), these data discredit these supposed climatically sensitive lithologies and facies used to separate "subpolar" Avalonia from the subtropical Moroccan margin of Gondwana. Landing et al should also take into consideration paleomagnetic data, which place Avalonia in mid-latitudes during this time interval (e.g., McNamara et al, 2001;Hamilton and Murphy, 2004;Waldron et al, 2022), and blatantly close to Morocco (Wen et al, 2020).…”