Structure and development of the southeast Newfoundland continental passive margin: derived from SCREECH Transect 3

Abstract

SUMMARY New seismic reflection data from the Grand Banks of Newfoundland and the Newfoundland Basin add to the growing knowledge of the composition, structure and history of this non‐volcanic margin. Geophysical imaging is now approaching the extent of that done previously on the conjugate margin along Iberia, providing a valuable database for the development of rifting models. Two parallel profiles over the shelf platform image deep crustal fabric representing Precambrian or possibly Appalachian deformation as well as Mesozoic extension. Progressively more intense extension of continental crust is imaged oceanwards without the highly reflective detachments frequently seen on profiles off Galicia. A landward‐dipping event ‘L’ is imaged sporadically and appears to be analogous to a similar event on the Iberian IAM9 profile. The transition zone is probably exposed serpentinized mantle as interpreted off the Iberian margin although there appears to be a difference in the character of ridge development and reflectivity. The distinctive ‘U’ reflection identified previously at the base of the Newfoundland Basin deep water sedimentary section and recently identified as one or more thin basalt sills is imaged on newly presented profiles that connect previously published profiles SCR3 and SCR2 showing that ‘U’ is highly regular and continuous except where interrupted by basement highs. ‘U’ is also seen to have a major impact on the ability to image underlying basement. A full transect beginning over completely unextended continental crust through to oceanic crust has provided a data set from which estimates of extension and the pre‐rifting location of the present continental edge can be made. Two estimates were obtained; 85 km based on faulting and 120 km based on crustal thickness.

Comparison of lithosphere structure across the Orphan Basin–Flemish Cap and Irish Atlantic conjugate continental margins from constrained 3D gravity inversions

“…2) have revealed a 120 km wide transitional zone outboard of volcanic basement, drilled within 30 km of thinned continental crust during the Deep Sea Drilling Project . This zone of transitional crust was subdivided into a landward 70 km zone of topographically subdued, exhumed serpentinized mantle peridotites (Bullock & Minshull 2005) similar to transitional crust interpreted further south on the Iberian and Newfoundland margins (Boillot et al 1987;Pickup et al 1996;Whitmarsh et al 1996;Chian et al 1999;Dean et al 2000;Lau et al 2006b;Sibuet et al 2007a;Tucholke & Sibuet 2007;Deemer et al 2009;Welford et al 2010b), and a less well-constrained 50 km zone of exhumed serpentinized basement ridges identified to the south on both margins (Boillot et al 1980;Beslier et al 1993;Shipboard Scientific Party 1998;Dean et al 2000;Henning et al 2004;van Avendonk et al 2006;Welford et al 2010b). …”

Structure and rifting evolution of the northern Newfoundland Basin from Erable multichannel seismic reflection profiles across the southeastern margin of Flemish Cap

“…1) are ideal locations for studying the dynamics of rifting since most of their extensional crustal structures have not been altered or obscured by magmatic processes. Consequently, these margins have been the focus of significant geophysical investigation (Boillot et al 1980, 1987; Shipboard Scientific Party 1987; Keen & de Voogd 1988; Mauffret et al 1989, Todd & Reid 1989; Tucholke et al 1989; Whitmarsh et al 1990; Pinheiro et al 1992, Beslier et al 1993; Whitmarsh et al 1993; Reid 1994; Sibuet et al 1995; Funck et al 2003, Henning et al 2004; Hopper et al 2004, 2006; Lau et al 2006a,b, Shillington et al 2006; van Avendonk et al 2006, Clark et al 2007; Afilhado et al 2008; Deemer et al 2009). While early attention was focused on central Iberia and Galicia Bank, seismic data coverage over the Newfoundland and Flemish Cap margins has increased to the point that better comparisons and interpretations are now possible for the conjugate pair.…”

“…On the Iberian and Galicia Bank margins, the nature of the transition zone has been well constrained from seismic profiling accompanied by extensive drilling. In the Newfoundland Basin, an increasing number of seismic surveys have illuminated the transition zone but with only one drillhole available for ground truthing (Shipboard Scientific Party 2004; Müntener & Manatschal 2006; Tucholke & Sibuet 2007), significant debate remains regarding the nature of this transitional crust (Lau et al 2006a,b; Shillington et al 2006; van Avendonk et al 2006, 2009; Deemer et al 2009).…”

Crustal structure of the Flemish Cap Continental Margin (eastern Canada): an analysis of a seismic refraction profile

“…Pickup et al 1996; Dean et al 2000; Shillington et al . 2006; Van Avendonk et al 2006; Deemer et al 2009). In the MCS profile, the morphology changes from a muted to a higher relief basement and the reflectivity becomes more disruptive around the ridge, which has the appearance of an extrusion of either volcanic and/or serpentinized mantle.…”