Stratigraphy, sedimentology and structure of the Oak Bay and Waweig formations, Mascarene Basin: implications for the paleotectonic evolution of southwestern New Brunswick

Abstract

The northwestern margin of the Mascarene Basin is preserved within a southeasterly dipping homocline in the Oak Bay area of southwestern New Brunswick. The Mascarene Group in this area comprises up to 600 m of massive, resedimented conglomerate of the Oak Bay Formation and approximately 4200 m of volcanic and resedimented volcaniclastic and siliciclastic sandstone and mudstone of the conformably overlying Waweig Formation. The Waweig Formation is formally subdivided into three members: a lower volcaniclastic-and felsic volcanic-dominated Campbell Point Member (~600 m thick), a medial grey to black shale-and mafic volcanic-dominated Sawyer Brook Member (-300 to 600 m thick), and an upper siliciclastic-dominated Simpson Comer Member with minor associated volcanic rocks (-3000 m thick). Five lithofacies recognized in the well-exposed Campbell Point Member include: (i) bedded tuffaceous sandstone facies, (it) chaotic tuffaceous sandstone facies, (iii) waterlain pyroclastic facies, (tv) medium-to thick-bedded sandstone facies, and (v) thin-bedded mudstone facies, all of which are products of sediment gravity flows. The massive conglomerates of the Oak Bay Formation were deposited as debris flows contemporaneous with faulting along the margin of the basin. Strata within the homocline possess a pervasive S, cleavage oriented approximately 35° oblique to bedding and a locally developed S2 cleavage; minor folds are rare and folds related to Sj are absent.Correlation with a more complete Siluro-Devonian sequence in an adjacent fault block in Maine suggests that the Oak Bay and Waweig formations are Late Silurian (Ludlovian-Pridolian). The volcanic centres in Maine were potential sources of much of the epiclastic and pyroclastic detritus in the Waweig Formation. Distinctive stratigraphic sections in more highly deformed fault blocks farther to the southeast attest to the composite architecture of the Mascarene Basin. Existing paleontological evidence may indicate that subsidence of these blocks occurred progressively later to the northwest as a result of sequential downfaulting.Consideration of the regional relationships between the Mascarene Basin with respect to the St. Croix Terrane and Fredericton Trough to the northwest and the New River Terrane to the southeast suggests that the basin developed by backarc rifting from the Silurian to Early Devonian and was flanked by a Late Ordovician to Silurian volcanic arc (Kingston Arc) to the southeast. 35, 59-84(1999) 0843-5561/99/010059-26S4.90/0

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

“…3), New River basement rocks of Panel C extend beneath the Silurian rocks of the Mascarene Group and beneath the Saint George Batholith as far north as the Turtle Head-Pendar Brook Fault (Thomas and Willis 1989;Whalen et al 1996a;Fyffe et al 1999;King and Barr 2004). Although basement rocks are concealed beneath Mascarene cover in the Passamaquoddy Bay area, the apparent westward continuation of Panel C into the Penobscot Bay area of Maine is overlain only in part by Silurian volcanic rocks.…”

“…In the Oak Bay area north of the Saint George Batholith (Figs. 3, 4), conglomerate of the Oak Bay Formation along the northern boundary of the Mascarene Basin is conformably overlain by light pink, fine-grained sandstone and siltstone; felsic crystal tuff; coarse-grained, volcaniclastic sandstone; and lesser mafic tuff and black shale of the Waweig Formation (Pickerill 1976;Fyffe et al 1999). A felsic tuff in the Waweig Formation yielded an Early Silurian (Llandoverian) U-Pb zircon date of 438 ± 4 Ma (Miller and Fyffe 2002).…”

“…More complexly deformed, steeply dipping rocks of the Mascarene Group to the southeast of the St. George-Fanning Brook Fault include limestones of the Upper Ordovician Goss Point Formation, quartzose sandstone of the Lower Silurian Back Bay Formation, and felsic and mafic tuffs of the Letete Formation (Cumming 1967;Donohoe 1973Donohoe , 1978Johnson and McLeod 1996;Fyffe et al 1999;McLeod et al 2001). Felsic tuff in the Letete Formation yielded an Early Silurian (Llandoverian) U-Pb zircon date of 437 ± 7 Ma (Miller and Fyffe 2002), coeval with felsic volcanism in the Kingston Group.…”

“…Dextral movement along this fault has juxtaposed the basal conglomerate of the Lower Silurian Oak Bay Formation against polydeformed Lower Ordovician black shale of the Calais Formation at Oak Bay and against Upper Ordovician quartzose sandstone of the Kendall Mountain Formation along strike to the northeast (Figs. 3, 4) (Ruitenberg and Ludman 1978;Gates 1989;Fyffe et al 1999;Park et al 2008;Thorne et al 2008).…”

“…Since 1990, in particular, a large amount of new stratigraphic, geochemical, geochronological, and structural data have been collected by van Staal and co-workers at the Geological Survey of Canada; Sandra Barr and students at Acadia University; Damian Nance at Ohio University; and staff of the Geological Surveys Branch at the New Brunswick Department of Natural Resources. This work involved detailed mapping of dozens of quadrangles throughout southern New Brunswick (Fyffe and Riva 1990;McLeod et al 1992McLeod et al , 2001McLeod 1995McLeod , 1997White 1996a, b, 1999;Johnson and McLeod 1996;White and Barr 1996;Currie and McNicoll 1999;Fyffe et al 1999;Fyffe 2001Fyffe , 2005Fyffe and Grant 2001;Barr et al 2002) and northern New Brunswick (Wilson 1990(Wilson , 2000(Wilson , 2002van Staal and Fyffe 1995;van Staal et al 2003;.…”