Deep seismic reflection data from the Bay of Fundy and Gulf of Maine: tectonic implications for the northern Appalachians

Abstract

Three deep-penetration seismic reflection profiles were collected off southwest Nova Scotia to determine the crustal structure and geometry beneath the Avalon and Meguma zones of the Appalachian Orogen in Canada. Onshore geological features have been traced seawards using new gravity and magnetic anomaly maps. The seismic data can also be correlated with the previous United States Geological Survey profile in the central Gulf of Maine.Two seismically distinct lower crustal blocks are identified: the Avalon and Sable lower crustal blocks, separated by a major north-dipping reflection zone that cuts the entire crust. The recognition of the Sable block adds a fourth block to the three already identified in the Canadian Appalachians. The Sable block is overlain by the Meguma Zone. The Avalon Zone overlies at least the northern part of the Avalon lower crustal block. Although offshore extension of geological features is not unequivocal, it appears that a north-dipping reflection zone southwest of Nova Scotia marks the site of Devonian thrusting of Avalon Zone over Meguma Zone. In the Bay of Fundy to the north, two south-dipping reflection zones are interpreted as major thrusts, possibly placing Avalon lower crust over a unit with different tectonic affinities. The Fundy Fault is a Carboniferous thrust within the Avalon block along the coast of New Brunswick; this was reactivated during Mesozoic extension as a transtensional fault. Extensional displacement farther southwest was probably accommodated along east-west-trending faults and small rift basins associated with them.

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

“…1). Geophysical data from the area (e.g., Hutchinson et al 1988;Keen et al 1991) are not sufficiently detailed to enable resolution of these details, but the results of this study are consistent *Analysed (except samples NB04-183b and c) by X-ray Fluorescence at the Regional Geochemical Centre, Saint Mary's University, Halifax, Nova Scotia. Major elements and some trace elements were measured using fused glass disks and other trace elements were measured using pressed powder pellets.…”

The Grand Manan Terrane of New Brunswick: Tectonostratigraphy and Relationship to the Gondwanan Margin of the Iapetus Ocean

“…Alternatively, the thrusting events on Grand Manan Island may be related to emplacement of Avalonia over Ganderia during the Acadian Orogeny (cf. Keen et al 1991). Similar thrusts are present along the Fundy coast on the mainland of New Brunswick, the Kennebecasis -Pocologan Fault being a prime example (Fig.…”

Petrology and U-Pb geochronology of buried Avalonian plutonic rocks on southeastern Cape Cod

“…The exact location of the Avalon-Meguma boundary in the Gulf of Maine is a matter of some debate. This boundary is well defined in northern Nova Scotia (see summary by Keen et al, 1991), from where it turns southeastward into the Gulf of Maine (Fig. 1).…”