A review of Proterozoic to Early Paleozoic lithotectonic terranes in ...

atlantic geology . volume 47 . 2011 213
Fig. 1. Lithotectonic divisions of the northeastern Appalachian orogen (after Hibbard et al. 2006).
tailed stratigraphic charts that accompany this text serve as an
update to those presented in an earlier terrane analysis of New
Brunswick by Fyffe and Fricker (1987).
GEOLOGICAL OVERVIEW OF
NEW BRUNSWICK TERRANES
Ruitenberg et al. (1977) were the first to describe a geological
zonation of New Brunswick and to present a general plate
tectonic model explaining the development of these zones. Subsequently,
Fyffe and Fricker (1987) applied the terrane concept
of Coney et al. (1980) to better constrain the timing of tectonic
events in the various zones by introducing the terms Avalonian,
Mascarene, St. Croix, Miramichi, and Elmtree terranes
(Figs. 2, 3). These terranes, following the concept of Williams
(1978, 1979), were distinguished on the basis of their distinctive
Lower Paleozoic lithotectonic sequences as compared with
adjacent fault blocks. The gathering of much new information
since the publication of Fyffe and Fricker (1987) has resulted
in the recognition of additional terranes in New Brunswick,
those being the Popelogan terrane of northern New Brunswick;
and the Caledonia, Brookville, New River, and Annidale terranes
of southern New Brunswick (Figs. 2, 3). The stratigraphy
and plutonic histories of these terranes are summarized below
in order to provide the regional geological context in which
to describe the Paleozoic plate tectonic evolution of the New
Brunswick segment of the Appalachian orogen. For detailed
kinematic analyses of some of the terrane-bounding faults in
New Brunswick, the reader is referred to Brown and Helmstaedt
(1970), Brown (1972), Garnett and Brown (1973), Park
et al. (1994, 2008), de Roo and van Staal (1994), and van Staal
and de Roo (1995).
The type Penobscot unconformity between Cambrian to
Lower Ordovician and Middle Ordovician sequences was defined
in north-central Maine by Neuman (1964) and subsequently
was recognized in northeastern New Brunswick by
Fyffe (1976, 1982). However, geological mapping and geochronological
studies only recently have provided definitive
evidence of Penobscot orogenesis in southern New Brunswick
(Johnson et al. 2009). Specifically, the Ganderian terranes in
the south (New River and Annidale, Fig. 3) have been shown
to contain Penobscot-related magmatism and tectonism. Consequently,
this paper emphasizes integrating the tectonic evolution
of the Ganderian terranes in southern New Brunswick
with those in the north. The northern terranes (Miramichi,
Elmtree, and Popelogan) are dominated by the previously
documented development and destruction of the Tetagouche
backarc basin, events that culminated in a younger period of
Late Ordovician to Silurian Salinic orogenesis (van Staal 1987,
1994; van Staal et al. 1990, 1991, 1996, 1998, 2003; van Staal
and Fyffe 1991, 1995).
As now understood, both of the microcontinents of Ganderia
and Avalonia are exotic to Laurentia, having rifted from
different parts of the Gondwanan margin by opening of the
Rheic Ocean in the Early Paleozoic. Specifically, Avalonia separated
from the West African craton or northeastern Amazonia
(McNamara et al. 2001; Murphy et al. 2002; Thompson et al.
2007, 2010; van Staal et al. 2009; van Staal and Barr in press),
and Ganderia separated from northwestern Amazonia (van
Staal et al. 1996, 2009; Schultz et al. 2008; Fyffe et al. 2009).
Contemporaneous extension along the Gondwanan margin
Fyffe et al. – A review of Proterozoic to Early Paleozoic lithotectonic terranes …
Copyright © Atlantic Geology, 2011