Extensional development of the Fundy rift basin, southeastern Canada

Abstract

The Fundy rift basin of Nova Scotia and New Brunswick, Canada, is part of the Eastern North American rift system that formed during the breakup of Pangaea. Integrated seismic-reflection, field, digital-elevation and aeromagnetic data indicate that the Fundy rift basin underwent two phases of deformation: syn-rift extension followed by post-rift basin inversion. Inversion significantly modified the geometries of the basin and its rift-related structures. In this paper, we remove the effects of inversion to examine the basin's extensional development. The basin consists of three structural subbasins: the Fundy and Chignecto subbasins are bounded by low-angle, NE-striking faults; the Minas subbasin is bounded by E-to ENE-striking faults that are steeply dipping at the surface and gently dipping at depth. Together, these linked faults form the border-fault system of the Fundy rift basin. Most major faults within the border-fault system originated as Palaeozoic contractional structures. All syn-rift units imaged on seismic profiles thicken towards the border-fault system, reflecting extensional movement from Middle Triassic (and possibly Permian) through Early Jurassic time. Intra-rift unconformities, observed on seismic profiles and in the field, indicate that uplift and erosion occurred, at least locally, during rifting. Based on seismic data alone, the displacement direction of the hanging wall of the border-fault system of the Fundy rift basin ranged from SW to SE during rifting. Field data (i.e. NEstriking igneous dykes, sediment-filled fissures and normal faults) indicate NW-SE extension during Early Jurassic time, supporting a SE-displacement direction. With a SE-displacement direction, the NE-striking border-fault zones of the Fundy and Chignecto subbasins had predominantly normal dip slip during rifting, whereas the E-striking border-fault zone of the Minas subbasin had oblique slip with left-lateral and normal components. Sequential restorations of seismic-reflection profiles (coupled with projections from onshore geology) show that the Fundy rift basin underwent 10-20 km of extension, most of which was accommodated by the border-fault system, and was considerably wider and deeper prior to basin inversion. Post-rift deformation tilted the eastern side of the basin to the northwest/north, producing significant uplift and erosion.

Rift-basin development: lessons from the Triassic–Jurassic Newark Basin of eastern North America

“…1), like the Newark Basin, were much larger during the final stages of rifting than they are today. For example, recent studies using seismic, field and/or vitrinitereflectance data show that the Fundy Basin (Withjack et al 1995(Withjack et al , 2009(Withjack et al , 2010, the Taylors were once larger, but subsequent erosion has reduced their widths considerably. These studies, together with this study of the Newark Basin and the mapped distribution of the rift basins ( Fig.…”

Stratigraphic and temporal context and faunal diversity of Permian-Jurassic continental tetrapod assemblages from the Fundy rift basin, eastern Canada

“…described by Olsen and Et-Touhami (2008), and the other in the foreshore at Lower Economy (45.3962°N, 63.9716°W) described in detail by Withjack et al (2009). The unconformity is also evident in the Consolidated Beacon Resources Ltd. Line 10 seismic profile described by Withjack et al (2010) over the Economy peninsula.…”

“…This is probably the best area to see the TS II -TS III unconformity in the Fundy basin. Withjack et al (2009) described less well-exposed outcrops of the unconformity on the cliffs and foreshore at Lower Economy. There, basal conglomeratic sandstones of the Red Head Member, gently dipping 16° west-southwest, rest unconformably on the Upper Carboniferous Mabou Group (Fig.…”

“…A3) on the shore. However, in the foreshore, where the Red Head Member dips 20° west and strikes 171°, it rests with a highly angular unconformity on Wolfville strata that dip on average about 57° south-southeast and strike 111° (Withjack et al 2009, fig. 11a).…”

An integrated study of Permo-Triassic basins along the North Atlantic passive margin: implication for future exploration

“…It represents a large complex Triassic half-graben (Wade et al 1996) with a strikeslip component of movement Withjack et al 1995Withjack et al , 2009 and is subdivided into three sub-basins; amongst them the easternmost Minas sub-basin shows the most extensive outcrops and preservation of sequences (Fig. 12).…”