Detrital zircon signatures in Precambrian and Paleozoic sedimentary units in southern New Brunswick – more pieces of the puzzle

Abstract

Southern New Brunswick consists of a complex collage of fault-bounded belts of Late Neoproterozoic igneous and metamorphic rocks, Early Paleozoic sedimentary, metamorphic and igneous units, and overlying Carboniferous sedimentary rocks. The area also contains the boundary between the Avalonian and Ganderian terranes as interpreted in the northern Appalachian orogen. New detrital zircon ages reported here provide improved understanding of depositional ages and provenance of diverse Neoproterozoic to Carboniferous rocks in this complex area. Detrital zircon data from samples with Neoproterozoic maximum depositional ages indicate a dominantly Gondwanan provenance with a strong influence from the Amazonian craton. However, quartzite from The Thoroughfare Formation on Grand Manan Island contains dominanly 2 Ga zircon grains, consistent with derivation from the West African Craton. The age spectrum is similar to that from the Hutchins Island Quartzite in the Isleboro block in Penobscot Bay, Maine, strengthening the previously proposed correlation between the two areas. Cambrian samples also show prominent peri-Gondwanan provenance with strong influence from Ediacaran to Early Cambrian arc magmatism. The maximum depositional ages of these samples are consistent with previous interpretations of Cambrian ages based on fossil correlations and field data. A Carboniferous sample from Avalonia shows a significant contribution from Devonian magmatism as the youngest detrital component, although its depositional age based on field relationships is Carboniferous. The results exemplify the need to integrate multiple datasets in making interpretations from detrital zircon data.

Cambrian syn‐rift tectonic pulses at unconformity‐bounded carbonates in the Avalon Zone of Newfoundland, Canada

“…Zircon data are also compatible with a Furongian to Early Ordovician separation of Avalonia from Gondwana based on (a) the presence of Mesoproterozoic (1.6‒1.0 Ga) and the absence of Palaeoproterozoic (2.5‒1.6 Ga) zircon grains in the Ediacaran rocks, which suggest that the source was the Amazonian craton; changing into (b) the absence of Mesoproterozoic zircon grains and the addition of 2000– and 800–Ma zircon populations in ‘lower Cambrian’ clastic rocks (Barr et al., 2012; McNamara et al., 2001; Pollock et al., 2009; Satkoski et al., 2010). This change in detrital zircon populations and drainage patterns has been interpreted in different ways, such as: (a) a progressive Ediacaran‒Cambrian rifting of Avalonia from the Amazonian margin coeval with the generation of topographical barriers along the Gondwanan margin, in a manner analogous to the Cenozoic rise of the Andes or the creation of the Basin‐and‐Range topography in the Western USA (Murphy, Fernández‐Suárez et al., 2004; Murphy, Pisarevsky et al., 2004); or (b) a transtensional rifting along dextral shearing strike‐slip faults from its original location, along the Amazonian margin, towards positions closer to the West African craton before starting its journey to Laurentia (for a recent updated revision of inherited zircon grains, see Barr et al., 2019).…”

U-Pb detrital zircon analysis of sedimentary rocks of the southeastern New England Avalon terrane in the U.S. Appalachians: Evidence for a separate crustal block

“…In Avalonian rocks in Canada, previous detrital zircon analyses yielded a predominant ca. 750-500 Ma population, and scattered ages up to Archean, suggesting an Amazonian origin (Keppie et al, 1998;Barr et al, 2003Barr et al, , 2012Barr et al, , 2019Murphy et al, 2004;Pollock et al, 2009;Satkoski et al, 2010;Henderson et al, 2016). Inherited zircon in igneous rocks in Avalonia yielded ca.…”

Age and tectonic setting of the Quinebaug-Marlboro belt and implications for the history of Ganderian crustal fragments in southeastern New England, USA

“…Considerable isotopic overlap exists between rocks identified as Ganderia and Avalonia (Fig. 25), and additional work is needed to fully characterize these two peri-Gondwanan terranes in southeastern New England and Atlantic Canada (Kerr et al, 1995;Samson et al, 2000;Barr et al 2003Barr et al , 2010Barr et al , 2019Murphy et al, 2009;van Staal and Barr, 2012). Our data compiled with Avalonian data (Fig.…”

“…2.2-2.0 Ga found in Avalonia yet they do show peaks from ca. 620-570 Ma which are common in both Ganderia and Avalonia (Pollock et al, 2009;Barr et al, 2019).…”