Detrital zircon ages from Neoproterozoic and Early Paleozoic conglomerate and sandstone units of New Brunswick and coastal Maine: implications for the tectonic evolution of Ganderia

Abstract

Detrital zircon ages were determined for conglomerate and sandstone samples from six fault-bounded belts in New Brunswick and coastal Maine. Formations sampled included the Martinon (Brookville belt), Flagg Cove (Grand Manan Island belt), Matthews Lake (New River belt), Ellsworth (Ellsworth belt), Calais (St. Croix belt), and Baskahegan Lake (Miramichi belt). Their maximum age of deposition is based on the youngest detrital zircon population and minimum age of deposition based on stratigraphic, paleontological, and cross-cutting intrusive relationships. The determined range of depositional ages are: Martinon between 602 ± 8 (youngest zircons) and 546 ± 2 Ma (age of cross-cutting intrusion); Flagg Cove between 574 ± 7 (youngest zircons) and 535 ± 3 Ma (age of cross-cutting intrusion); Matthews Lake between 539 ± 5 (youngest zircons) and 514 ± 2 Ma (age of overlying volcanic rocks); Ellsworth between 507 ± 6 (youngest zircons) and 504 ± 3 Ma (age of overlying volcanic rocks); Calais between 510 ± 8 (youngest zircons) and 479 ± 2 Ma (graptolite zone); and Baskahegan Lake between 525 ± 6 (youngest zircons) and 488 ± 2 Ma (graptolite zone).All samples are dominated by Neoproterozoic (Gondwanan) zircon populations. The Early Paleozoic Matthews Lake, Ellsworth, and Calais formations contain main population peaks at 539 ± 5 Ma, 545 ± 4 Ma, and 556 ± 7 Ma, respectively, consistent with derivation mainly from magmatic rocks of the Brookville, Grand Manan Island, and/or New River belts, previously dated at ~553 to ~528 Ma. In contrast, the main peak in the Early Paleozoic Baskahegan Lake Formation is older at 585 ± 5 Ma. The main peak in the Neoproterozoic to Early Cambrian Flagg Cove Formation is at 611 ± 7 Ma with a secondary peak at 574 ± 7 Ma; the former was likely derived from locally exposed igneous units dated at ~618 to ~611 Ma. The Neoproterozoic Martinon Formation exhibits dominant peaks at 674 ± 8 Ma and 635 ± 4 Ma. Ganderian basement gneiss dated at ~675 Ma and intruded by plutonic rocks dated at ~584 Ma in the Hermitage Flexure of Newfoundland are possible sources for these older zircon components in the Martinon and Baskahegan Lake formations. Plutonic rocks in the New River belt dated at ~629 to ~622 Ma may be the source of the younger component in the Martinon Formation.The samples also contain a small number of Mesoproterozoic, Paleoproterozoic, and Archean zircon grains, the latter as old as 3.23 Ga. The presence of zircons in the range 1.07 to 1.61 Ga is consistent with an origin along the periGondwanan margin of Amazonia rather than West Africa. The general similarity of zircon provenance for samples from New Brunswick and coastal Maine suggests that all the Ganderian belts were part of a single microcontinent rifted from the Amazonian craton.The Grand Manan Island and New River belts both record two distinct periods of Neoproterozoic arc magmatism (~629 to ~611 Ma and at ~553 to ~535 Ma) whereas the Brookville belt experienced only a single period of arc magmatism lasting from ~553 to ~528 Ma. ...

A Review of Proterozoic to Early Paleozoic Lithotectonic Terranes in New Brunswick, Canada and their Tectonic Evolution during Penobscot, Taconic, Salinic and Acadian Orogenesis

“…It was previously referred to as the Mascarene terrane by Fyffe and Fricker (1987), because the nature of the basement rocks beneath the Silurian Mascarene cover was poorly known at the time (Hay 1968;Rast and Currie 1976). Basement rocks of the New River terrane trend toward coastal Maine, where they may underlie Penobscot volcanic rocks of the Ellsworth terrane (Stewart et al 1995;Fyffe et al 2009). The Ellsworth and New River terranes are cut internally by multiple faults constituting a large dextral transcurrent fault system that includes Acadian strike-slip duplexes of Late Silur-Copyright © Atlantic Geology, 2011 Fyffe et al -A review of Proterozoic to Early Paleozoic lithotectonic terranes … ian to Early Devonian age (Leger and Williams 1986;West et al 1992West et al , 1995Stewart et al 1995;Hibbard et al 2006;Lin et al 2007;van Staal et al 2009).…”

“…Specifically, Avalonia separated from the West African craton or northeastern Amazonia (McNamara et al 2001;Murphy et al 2002;Thompson et al 2007Thompson et al , 2010; van Staal et al 2009;van Staal and Barr in press), and Ganderia separated from northwestern Amazonia Schultz et al 2008;Fyffe et al 2009). Contemporaneous extension along the Gondwanan margin and Kerr 1997).…”

“…Both of these formations represent older passive-margin sequences unrelated to Iapetus closure (Hofmann 1974;Nance 1987;Currie 1991;White and Barr 1996). The Ashburn and Martinon formations cannot be older than 1.23 ± 0.003 Ga and 602 ± 8 Ma, respectively, according to their youngest contained detrital zircon populations (Barr et al 2003c;Fyffe et al 2009). The Brookville Gneiss, a unit of paragneiss and orthogneiss, is in sheared contact with the Green Head Group; the orthogneiss yielded a U-Pb zircon date of 605 ± 3 Ma Dallmeyer et al 1990).…”

Age and petrology of the Machias Seal Island quartz monzodiorite, the southernmost rocks in New Brunswick, Canada

“…Fyffe, 2003). The similarity between Grand Manan Island and the New River terrane in rock types, Sm-Nd isotopic characteristics, and ages has been used to infer a link between those two areas, and for including both of them, as well as the Brookville terrane, in Ganderia (Barr et al 2003;Miller et al 2007;Fyffe et al 2009). As documented in detail by Barr et al (2003) and also discussed in subsequent papers (e.g., Miller et al 2007;Fyffe et al 2009), differences in rock types and ages indicate that none of these areas is likely to be related to the Avalonian Caledonia terrane.…”

“…Geological studies on nearby Grand Manan Island (Fig. 1) have not resolved that problem, as rocks there have equivocal terrane affinity (e.g., Miller et al 2007;Fyffe et al 2009). However, they most resemble those of the New River terrane of southern New Brunswick, suggesting that the Ganderian Kingston and Brookville belts, as well as Avalonia and Meguma, all lie outboard of Grand Manan Island (Fig.…”