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North Atlantic bathymetric map (Smith & Sandwell 1997) showing features of the conjugate margins of the Newfoundland –Iberia rift. Boxes locate Figures 2 & 3. White dashed lines show Palaeozoic sutures and terrane boundaries in continental crust (after Keen et al. 1990; Silva et al. 2000) and black lines delineate major rift basins. Yellow line in the Tagus Abyssal Plain locates refraction profile of Pinheiro et al. (1992) (Fig. 4g, section I1). AM, Armorican Massif; BB, Bay of Biscay; CA, Collector magnetic anomaly; CIZ, Central Iberian Zone; CZ, Cantabrian Zone; F, Flemish Pass Basin; FC, Flemish Cap; GB, Galicia Bank; GI, Galicia Interior Basin; GRB, Gorringe Bank; GZ, Galicia-Tr ́s-os-Montes Zone; H, Horseshoe Basin; IAA, Ibero-Armorican Arc that presumably connected to the northern European sutures prior to opening of the Bay of Biscay; IAP, Iberia Abyssal Plain; J, Jeanne d’Arc Basin; JAR, J Anomaly Ridge; L, Lusitanian Basin; MAR, Mid-Atlantic Ridge; MEG, Meguma Terrane; MTR, Madeira– Tore Rise; NNB, northern Newfoundland Basin; NS, Newfoundland Seamounts; O, Orphan Basin; OMZ, Ossa Morena Zone; P, Porto Basin; SB, Salar– Bonnition Basin; SENR, Southeast Newfoundland Ridge; SNB, southern Newfoundland Basin; SPZ, South Portuguese Zone; TAP, Tagus Abyssal Plain; TS, Tore Seamounts; W, Whale Basin; WZ, Western Asturian–Leonese Zone.
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The Newfoundland-Iberia rift is considered to be a type example of a non-volcanic rift. Key features of the conjugate margins are transition zones (TZs) that lie between clearly continental crust and presumed normal (Penrose-type) oceanic crust that appears up to 150-180 km farther seaward. Basement ridges drilled in the Iberia TZ consist of exhume...
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... Newfoundland margin is dominated by a broad, shallow-water (,100 m) platform that forms the Grand Banks (Fig. 1). This platform is formed by thick continental crust (27 -35 km: Reid 1988;) that is deeply incised by large, deep rift basins. The seaward edge of the plat- form is a seaward-dipping basement hinge zone that runs mostly beneath the continental slope from the southern transform margin of the Grand Banks northwards to Flemish Cap. Along ...
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... Iberia margin contrasts with the Newfoundland margin in that it has a much nar- rower continental shelf and limited development of rift basins in thick continental crust (Fig. 1). The principal rift basin in the shallow Iberia margin is the Lusitanian Basin, which is roughly co-linear with the Porto Basin beneath the continen- tal shelf and slope and with the deep-water Galicia Interior Basin to the north. Thinned continental crust underlies both the Galicia Interior Basin and Galicia Bank to the west ( Boillot ...
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... seismic reflection and magnetic- anomaly studies that Tithonian-Hauterivian sea- floor spreading formed the TZ, prior to a westward ridge jump at chron M10. However, a refraction profile shot over this area ( Pinheiro et al. 1992) ident- ified exceptionally thin 'crust' (2 km) that overlies mantle with low velocities of 7.6-7.9 km s 21 ( Fig. 4g, section I1), very much like the IAM9 base- ment farther north under the Iberia Abyssal Plain. Pinheiro et al. (1992) interpreted the Tagus basement to be formed by sea-floor spreading beginning at chron M11, but they noted that the low mantle velocities may indicate widespread serpentiniza- tion. In the conjugate Newfoundland TZ, Reid (1994) ...
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... and not topography. Three sections are arranged from south to north (left to right) for each of the Newfoundland (N) and Iberia (I) margins. Sections N3 and I3 are conjugates, I2 is offset about 25 km south of N2 at anomaly M0, and N1 and I1 are approximately conjugate. Locations of sections are shown in Figures 2 and 3 (I1 is located in Fig. 1). Pale blue and pale green colours indicate thickness of interpreted oceanic and transitional 'crust', respectively. These have compressional wave velocities in the range of 3.5-7.2 km s 21 and commonly exhibit steep velocity gradients. The oceanic layer is anomalously thick at the young end of section I2 because the profile intersects ...
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... the southern margin of the rift from about the time of chron M4 to a time younger than M0 (Tucholke & Ludwig 1982) (Fig. 4c; see the subsec- tion on 'Rift magmatism' later). The anomaly amplitude is highest at the southern edge of the rift in the area of the Southeast Newfoundland Ridge (SENR), J Anomaly Ridge (JAR) and Madeira-Tore Rise (MTR) (Fig. 1); away from this area the high amplitude is confined to the zone around chrons M1 and M0 ( Rabinowitz et al. 1978). Within the Newfoundland-Iberia rift the anomaly gradually loses its high amplitude north of the Newfoundland Seamounts and Tore Seamount on the Newfoundland and Iberia margins, respect- ively (bold lines, Figs 2 & 3). ...
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... M3 on the Iberia margin ( Figs 3 & 4g, section I2), is serpentinized peridotite with minor gabbro intrusions ( Whitmarsh et al. 1998). Base- ment at Site 1277 near anomaly M1 off Newfound- land is also serpentinized peridotite beneath a thin interval of allochthonous basaltic, gabbroic and ser- pentinite debris (Figs 2 & 4g, section N2; see also Fig. 10 later) ( Tucholke et al. 2004). It is well known that serpentinized peridotites can have compressional-wave velocities ranging from less than 5 km s 21 up to normal mantle velocities of 8þ km s 21 , depending on the degree of serpentini- zation (e.g. Christensen 2004). Thus, in the absence of other constraints such as Poisson's ratio ...
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... Newfoundland- Iberia rift developed was an assemblage of Precam- brian-Palaeozoic rocks that accreted during the closing of the Palaeozoic Iapetus and Rheic oceans. Along the present Atlantic Canadian margin these rocks form the Appalachian Orogen, and from NW to SE they appear in three terranes comprising the Dunnage, Gander and Avalon zones ( Fig. 1) (Williams & Hatcher 1982, 1983. The Avalon Zone occupies easternmost Newfound- land and most of the Grand Banks platform. Another zone (Meguma) lies south of the Avalon terrane at the southern edge of the Grand Banks, and a prominent magnetic anomaly (Collector Anomaly) marks its northern boundary. The first three terranes were ...
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... basement of the Iberia margin was accreted by closure of Palaeozoic ocean basins and suturing during the Hercynian (Variscan) orogeny in approximately Middle Devonian -Carboniferous time, i.e. at the same time as the late Acadian and Alleghenian orogenies in North America. In Iberia, the accreted terranes have NW-SE orientations (Fig. 1); offshore, they are thought to have curved back to the NE and east to form the Ibero-Armorican Arc, continuous with approximately east-west sutures in NW France (Armorican Massif ), SW Britain and Germany (Ziegler 1982;Capdevila & Mougenot 1988;Silva et al. 2000). These terranes were intruded by large granitoid batholiths both during ...
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... between Newfoundland and Iberia occurred primarily in two phases. The initial phase occurred in the Late Triassic -earliest Jurassic, at which time rift basins formed over a broad region within the Grand Banks (e.g. Jeanne d'Arc, Whale and Horseshoe basins; Fig. 1) and the Iberia margin (Lusitanian Basin, possibly Porto and Galicia Interior basins: Murillas et al. 1990). The Grand Banks basins accumulated siliciclastic 'red-bed' sediments during Carnian-Norian time, and these were suc- ceeded by evaporite deposits that reached into the earliest Jurassic (Hettangian-Sinemurian) in both the Grand ...
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... the rift dates to the Barremian-early Aptian (approxi- mately chron M4 to younger than M0; Fig. 4c) (Tucholke & Ludwig 1982). At this time the SENR and JAR formed on the North American side of the plate boundary, and the conjugate MTR and perhaps parts of Gorringe Bank (GRB; later deformed during the Cenozoic) were emplaced on the Iberia side (Fig. 1). Magmatism was centred at the southern edge of the rift in the position of the SENR -GRB, and at approximately chron M2-M0 (Barremian) it was channelled both southwards along the Mid-Atlantic Ridge axis to form the JAR -MTR (Tucholke & Ludwig 1982) and north- wards into the Newfoundland -Iberia rift to form comparable basement edifices ...
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... SENR -GRB, and at approximately chron M2-M0 (Barremian) it was channelled both southwards along the Mid-Atlantic Ridge axis to form the JAR -MTR (Tucholke & Ludwig 1982) and north- wards into the Newfoundland -Iberia rift to form comparable basement edifices that reach toward the present positions of the Newfoundland Sea- mount and Tore Seamounts (Fig. 1) ...
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... magmatism in the Newfoundland Basin is observed in the form of diabase sills that were injected into sediments at and below the U reflec- tion at ODP Site 1276 during late Albian -early Cenomanian time (105 -98 Ma;Hart & Blusztajn 2006). These sills are not clearly observed in seismic reflection records around the drill site (Fig. 10), but probable sills at this stratigraphic level appear in profiles from the southern part of the basin (Fig. 11). The source of the magma is uncertain, but it may have been associated with for- mation of the Newfoundland Seamounts near the centre of the basin (Karner & Shillington 2005); a single age date indicates that one of these ...
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... into sediments at and below the U reflec- tion at ODP Site 1276 during late Albian -early Cenomanian time (105 -98 Ma;Hart & Blusztajn 2006). These sills are not clearly observed in seismic reflection records around the drill site (Fig. 10), but probable sills at this stratigraphic level appear in profiles from the southern part of the basin (Fig. 11). The source of the magma is uncertain, but it may have been associated with for- mation of the Newfoundland Seamounts near the centre of the basin (Karner & Shillington 2005); a single age date indicates that one of these sea- mounts formed at 97.7 + 1.5 Ma (Sullivan & Keen 1977). Only minor magmatism of this age is documented on the ...
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... there is a conflict between pre- viously described evidence for extension during Barremian-Aptian time and the corresponding structural and stratigraphic record as imaged in seismic reflection records both over continental crust of Galicia Bank and over the Newfoundland and Iberia TZs. Sediments of this age in seismic sequence 4 off Iberia and sequence A off Newfoundland (Fig. 4b) are mostly horizontal, and they rarely are faulted or show splayed reflec- tions that we would expect if they were deposited over rotating fault blocks during extension (Figs 5-15). ...
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... below the U reflection (Aptian event) is poorly imaged because of the strong reflectivity of U, because of low impedance contrasts, or both. Short sections of high-amplitude reflections near the level of U probably are diabase sills, similar to those drilled at this stratigraphic level at ODP Site 1276 in the northern part of the basin (see Fig. ...
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... significant change in crustal thickness from the outer limit of continental crust (Fig. 2) seaward to the end of the refraction profile on approximately 114 Ma crust (Fig. 4g, section N2). Although Van Avendonk et al. (2006) interpreted most of this as thin oceanic crust, the recovery of peridotite basement at ODP Site 1277 seaward of anomaly M1 (Fig. 10) suggests that the basement may be domi- nantly exhumed mantle. A similar conclusion might be drawn for the Iberia side, where peridotite basement was drilled at ODP Site 1070 near anomaly M2 (open circle at youngest peridotite ridge: Fig. 4g, section I2) (Whitmarsh & Wallace ...
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... by several notable features in reflection profiles. Normally they are relatively flat-lying and their internal reflections are parallel to subparallel (Figs 5, 6, 8 & 9). Where reflections diverge, their spacing usually increases toward basin centres rather than towards footwall fault blocks. Faulting and rotation of the sequences (e.g. Fig. 10) are not common but are observed in scattered locations, including the eastern margin of Galicia Bank (PérezGussinyé et al. 2003). Thus, most basins accumu- lated sediments in the absence of obvious ...
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... sequence 4 fills valleys between peridotite ridges on the Iberia margin, its reflectivity appears to be related to the basement composition. The rounded shape of peridotite ridge crests, as well as possible slumps and debris slides (Figs 12 & 14), suggests that the serpentinite was weak and mobile. In fact, drilling of peridotite ridges within the rift has consistently recovered serpentinite breccias and olis- tostromes that reflect mass wasting of the serpenti- nized basement (Whitmarsh et al. 1998;Tucholke et al. 2004). ...
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... other cases, mass wasting from both peridotite ridges and continental fault blocks is demonstrated by chaotic fill (Figs 7b & 12) and by instances where sequence 4 laps high onto the bounding fault blocks (Figs 6b & 8c). Where cored at ODP Sites 897 and 899 (see Fig. 12a), these materials are serpentine-rich olistostromes and breccias that were emplaced before faulting and uplift of the underlying peridotite ridges ( Comas et al. 1996;Gibson et al. 1996). ...
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... other cases, mass wasting from both peridotite ridges and continental fault blocks is demonstrated by chaotic fill (Figs 7b & 12) and by instances where sequence 4 laps high onto the bounding fault blocks (Figs 6b & 8c). Where cored at ODP Sites 897 and 899 (see Fig. 12a), these materials are serpentine-rich olistostromes and breccias that were emplaced before faulting and uplift of the underlying peridotite ridges ( Comas et al. 1996;Gibson et al. 1996). Thus, some ridge-flank deposits identified in reflection profiles may predate exten- sion (e.g. Fig. 12b, right-hand side), although thickening of ...
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... 6b & 8c). Where cored at ODP Sites 897 and 899 (see Fig. 12a), these materials are serpentine-rich olistostromes and breccias that were emplaced before faulting and uplift of the underlying peridotite ridges ( Comas et al. 1996;Gibson et al. 1996). Thus, some ridge-flank deposits identified in reflection profiles may predate exten- sion (e.g. Fig. 12b, right-hand side), although thickening of the deposits in valleys shows that mass wasting also occurred during or after the fault- ing. Elsewhere, the ridge-flank deposits clearly were emplaced following extension, and their configur- ation shows that they were derived largely from the local topography (Figs 6b & ...
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... above patterns are not well defined in sequence A in the Newfoundland Basin, although rounding of presumed serpentinite ridges and poss- ible displacement of allochthonous blocks and debris are observed (Figs 10a & 13). Tucholke et al. (1989) observed rare instances where the Aptian event (U reflection) at the top of the sequence appears to truncate basement topography. ...
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... et al. (1989) observed rare instances where the Aptian event (U reflection) at the top of the sequence appears to truncate basement topography. A similar possible occurrence is shown on the left of Figure 13b. If these basement highs consisted of exceptionally weak serpentinite, it is conceivable that their exposed tops were eroded away by mass wasting or even by passing turbidity currents. ...
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... is masked ( Figs 11 & 15). Either the impedance of sequence A is so high that signal penetration is limited, the impe- dance contrast with basement is small (e.g. the shallow basement is strongly serpentinized), or both. In the northern part of the basin the masking is reduced, although deeper structure often is still difficult to detect (Fig. 10a). A major unconformity was eroded across the southern Grand Banks during the Early Cretaceous in response to deformation and doming associated with the Avalon uplift (e.g. Grant et al. 1988), and it is likely that coarse clastics shed from this region help to account for the strong reflectivity in at least the central to southern New- ...
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... et al. 1988), and it is likely that coarse clastics shed from this region help to account for the strong reflectivity in at least the central to southern New- foundland Basin. Off Iberia the Aptian event (orange reflection) is locally strong, but it generally has lower amplitude than off Newfoundland and it seldom masks underlying structure except where debris has been shed from peridotite ridges (Figs 6a & 14). ...
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... sequences 3 and B characteristically lap unconformably onto underlying sequences 4 and A, respectively (Figs 5-8 & 12 -15). This implies either a tectonic event or a sharp change in sedimen- tation pattern, or both, at the Aptian -Albian boundary. ...
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... A, late Aptian (Fig. 16a). Up to this time, sea floor was being emplaced primarily by exhumation of subcontinental mantle, and in-plane tensile stres- ses were elevated throughout the rift. The plates extended internally in local weak zones, probably where existing faults were highly serpentinized. Mass wasting and slumps contributed coarse, reflec- tive, ...
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... B, Aptian-Albian boundary (Fig. 16b). Normal sea-floor spreading began in latest Aptian -earliest Albian time. This introduction of heat and melt at the plate boundary caused in-plane tensile stress to drop sharply, resulting in a pulse of relative compression in the adjoining plates. The compression may have amplified topo- graphy in the deep basins and thus briefly ...
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... change in stress regime probably also caused differential vertical motions on the proximal continental margins, sti- mulating erosion and sediment transport to the (a) Section of ISE 10 multichannel reflection profile SW of Galicia Bank, just north of the ODP Leg 149-173 drilling transect. Location in Figure 3 (ISE 10W). Magnetic anomalies M1 and M3 are identified. ...
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... C, Albian (Fig. 16c). Following the Aptian event, relaxation of stresses reduced long- wavelength flexural topography, and sediment flux to the basins was attenuated. Slopes on basement highs also equilibrated, and there no longer was sig- nificant mass wasting from these sources. Fine- grained turbidity currents spread widely across the basins and lapped ...
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... continental crust probably soled out in serpentinized mantle, the continental faults overall were probably stronger than those in the exhumed mantle. Thus, we suggest that during Barremian-Aptian time there was very limited extension in continental crust and that most intra- plate extension occurred within areas of exhumed, serpentinized mantle (Fig. ...
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... that the period of amag- matic rifting leading to this event can be protracted if the extension rate is low and if the lithosphere is homogeneous, or if the lithosphere is heterogeneous and zones of crustal and mantle weakness are offset from one another. In the Newfoundland -Iberia rift, both the heterogeneity of the prerift Palaeozoic crust (Fig. 1) and the observed spatial and temporal shifts in the locus of rifting suggest that the latter may be the case. Reston & Phipps Morgan (2004) proposed that the onset of sea-floor spreading might be triggered by invasion of melt and heat from an adjacent rift segment or mantle plume. In the present instance, this seems unlikely because ...
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... character of the Aptian event is consistent with this postulated stress change. Relative com- pression may have amplified local basement topo- graphy and stimulated mass wasting, as suggested by chaotic deposits at the top of sequence 4 off Iberia (Figs 8c & 14b). It may also have enhanced the curvature of the Aptian-event reflection and even caused reverse faulting (Fig. 13b). ...
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... event is consistent with this postulated stress change. Relative com- pression may have amplified local basement topo- graphy and stimulated mass wasting, as suggested by chaotic deposits at the top of sequence 4 off Iberia (Figs 8c & 14b). It may also have enhanced the curvature of the Aptian-event reflection and even caused reverse faulting (Fig. 13b). Unfortu- nately, any reverse faulting that may have devel- oped on the Iberia margin has been obscured by the effects of Cenozoic compression (e.g. Fig. 12) (Boillot et al. 1979;Masson et al. ...
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... suggested by chaotic deposits at the top of sequence 4 off Iberia (Figs 8c & 14b). It may also have enhanced the curvature of the Aptian-event reflection and even caused reverse faulting (Fig. 13b). Unfortu- nately, any reverse faulting that may have devel- oped on the Iberia margin has been obscured by the effects of Cenozoic compression (e.g. Fig. 12) (Boillot et al. 1979;Masson et al. ...
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... is likely that the stress change was accompanied by long-wavelength differential verti- cal motions along the proximal margins (Fig. 16b). Numerical models indicate that release of in-plane tensile stress would cause uplift of the proximal rift basin (lower continental slope and continental rise), subsidence of the distal rift basin and the outer shelf, and uplift of the inner shelf and coastal plain (e.g. Braun & Beaumont 1989;Kooi & Cloetingh 1992). Details of ...
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... numerical models (e.g. Kooi & Cloetingh 1992) suggest that the long-wavelength vertical dis- tortion of the lithosphere caused by relative com- pression would have decayed rapidly (Fig. 16c). With the introduction of a new and relatively stable stress regime, regional flux of coarse sedi- ments in debris flows and turbidity currents would have been sharply curtailed. Slope stabilization probably also resulted in a rapid reduction of mass wasting in local basins between basement ridges on the distal margins. Thus, ...
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... Newfoundland margin is dominated by a broad, shallow-water (,100 m) platform that forms the Grand Banks (Fig. 1). This platform is formed by thick continental crust (27 -35 km: Reid 1988;) that is deeply incised by large, deep rift basins. The seaward edge of the plat- form is a seaward-dipping basement hinge zone that runs mostly beneath the continental slope from the southern transform margin of the Grand Banks northwards to Flemish Cap. Along ...
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... Iberia margin contrasts with the Newfoundland margin in that it has a much nar- rower continental shelf and limited development of rift basins in thick continental crust (Fig. 1). The principal rift basin in the shallow Iberia margin is the Lusitanian Basin, which is roughly co-linear with the Porto Basin beneath the continen- tal shelf and slope and with the deep-water Galicia Interior Basin to the north. Thinned continental crust underlies both the Galicia Interior Basin and Galicia Bank to the west ( Boillot ...
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... seismic reflection and magnetic- anomaly studies that Tithonian-Hauterivian sea- floor spreading formed the TZ, prior to a westward ridge jump at chron M10. However, a refraction profile shot over this area ( Pinheiro et al. 1992) ident- ified exceptionally thin 'crust' (2 km) that overlies mantle with low velocities of 7.6-7.9 km s 21 ( Fig. 4g, section I1), very much like the IAM9 base- ment farther north under the Iberia Abyssal Plain. Pinheiro et al. (1992) interpreted the Tagus basement to be formed by sea-floor spreading beginning at chron M11, but they noted that the low mantle velocities may indicate widespread serpentiniza- tion. In the conjugate Newfoundland TZ, Reid (1994) ...
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... and not topography. Three sections are arranged from south to north (left to right) for each of the Newfoundland (N) and Iberia (I) margins. Sections N3 and I3 are conjugates, I2 is offset about 25 km south of N2 at anomaly M0, and N1 and I1 are approximately conjugate. Locations of sections are shown in Figures 2 and 3 (I1 is located in Fig. 1). Pale blue and pale green colours indicate thickness of interpreted oceanic and transitional 'crust', respectively. These have compressional wave velocities in the range of 3.5-7.2 km s 21 and commonly exhibit steep velocity gradients. The oceanic layer is anomalously thick at the young end of section I2 because the profile intersects ...
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... the southern margin of the rift from about the time of chron M4 to a time younger than M0 (Tucholke & Ludwig 1982) (Fig. 4c; see the subsec- tion on 'Rift magmatism' later). The anomaly amplitude is highest at the southern edge of the rift in the area of the Southeast Newfoundland Ridge (SENR), J Anomaly Ridge (JAR) and Madeira-Tore Rise (MTR) (Fig. 1); away from this area the high amplitude is confined to the zone around chrons M1 and M0 ( Rabinowitz et al. 1978). Within the Newfoundland-Iberia rift the anomaly gradually loses its high amplitude north of the Newfoundland Seamounts and Tore Seamount on the Newfoundland and Iberia margins, respect- ively (bold lines, Figs 2 & 3). ...
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... M3 on the Iberia margin ( Figs 3 & 4g, section I2), is serpentinized peridotite with minor gabbro intrusions ( Whitmarsh et al. 1998). Base- ment at Site 1277 near anomaly M1 off Newfound- land is also serpentinized peridotite beneath a thin interval of allochthonous basaltic, gabbroic and ser- pentinite debris (Figs 2 & 4g, section N2; see also Fig. 10 later) ( Tucholke et al. 2004). It is well known that serpentinized peridotites can have compressional-wave velocities ranging from less than 5 km s 21 up to normal mantle velocities of 8þ km s 21 , depending on the degree of serpentini- zation (e.g. Christensen 2004). Thus, in the absence of other constraints such as Poisson's ratio ...
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... Newfoundland- Iberia rift developed was an assemblage of Precam- brian-Palaeozoic rocks that accreted during the closing of the Palaeozoic Iapetus and Rheic oceans. Along the present Atlantic Canadian margin these rocks form the Appalachian Orogen, and from NW to SE they appear in three terranes comprising the Dunnage, Gander and Avalon zones ( Fig. 1) (Williams & Hatcher 1982, 1983. The Avalon Zone occupies easternmost Newfound- land and most of the Grand Banks platform. Another zone (Meguma) lies south of the Avalon terrane at the southern edge of the Grand Banks, and a prominent magnetic anomaly (Collector Anomaly) marks its northern boundary. The first three terranes were ...
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... basement of the Iberia margin was accreted by closure of Palaeozoic ocean basins and suturing during the Hercynian (Variscan) orogeny in approximately Middle Devonian -Carboniferous time, i.e. at the same time as the late Acadian and Alleghenian orogenies in North America. In Iberia, the accreted terranes have NW-SE orientations (Fig. 1); offshore, they are thought to have curved back to the NE and east to form the Ibero-Armorican Arc, continuous with approximately east-west sutures in NW France (Armorican Massif ), SW Britain and Germany (Ziegler 1982;Capdevila & Mougenot 1988;Silva et al. 2000). These terranes were intruded by large granitoid batholiths both during ...
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... between Newfoundland and Iberia occurred primarily in two phases. The initial phase occurred in the Late Triassic -earliest Jurassic, at which time rift basins formed over a broad region within the Grand Banks (e.g. Jeanne d'Arc, Whale and Horseshoe basins; Fig. 1) and the Iberia margin (Lusitanian Basin, possibly Porto and Galicia Interior basins: Murillas et al. 1990). The Grand Banks basins accumulated siliciclastic 'red-bed' sediments during Carnian-Norian time, and these were suc- ceeded by evaporite deposits that reached into the earliest Jurassic (Hettangian-Sinemurian) in both the Grand ...
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... the rift dates to the Barremian-early Aptian (approxi- mately chron M4 to younger than M0; Fig. 4c) (Tucholke & Ludwig 1982). At this time the SENR and JAR formed on the North American side of the plate boundary, and the conjugate MTR and perhaps parts of Gorringe Bank (GRB; later deformed during the Cenozoic) were emplaced on the Iberia side (Fig. 1). Magmatism was centred at the southern edge of the rift in the position of the SENR -GRB, and at approximately chron M2-M0 (Barremian) it was channelled both southwards along the Mid-Atlantic Ridge axis to form the JAR -MTR (Tucholke & Ludwig 1982) and north- wards into the Newfoundland -Iberia rift to form comparable basement edifices ...
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... SENR -GRB, and at approximately chron M2-M0 (Barremian) it was channelled both southwards along the Mid-Atlantic Ridge axis to form the JAR -MTR (Tucholke & Ludwig 1982) and north- wards into the Newfoundland -Iberia rift to form comparable basement edifices that reach toward the present positions of the Newfoundland Sea- mount and Tore Seamounts (Fig. 1) ...
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... magmatism in the Newfoundland Basin is observed in the form of diabase sills that were injected into sediments at and below the U reflec- tion at ODP Site 1276 during late Albian -early Cenomanian time (105 -98 Ma;Hart & Blusztajn 2006). These sills are not clearly observed in seismic reflection records around the drill site (Fig. 10), but probable sills at this stratigraphic level appear in profiles from the southern part of the basin (Fig. 11). The source of the magma is uncertain, but it may have been associated with for- mation of the Newfoundland Seamounts near the centre of the basin (Karner & Shillington 2005); a single age date indicates that one of these ...
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... into sediments at and below the U reflec- tion at ODP Site 1276 during late Albian -early Cenomanian time (105 -98 Ma;Hart & Blusztajn 2006). These sills are not clearly observed in seismic reflection records around the drill site (Fig. 10), but probable sills at this stratigraphic level appear in profiles from the southern part of the basin (Fig. 11). The source of the magma is uncertain, but it may have been associated with for- mation of the Newfoundland Seamounts near the centre of the basin (Karner & Shillington 2005); a single age date indicates that one of these sea- mounts formed at 97.7 + 1.5 Ma (Sullivan & Keen 1977). Only minor magmatism of this age is documented on the ...
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... there is a conflict between pre- viously described evidence for extension during Barremian-Aptian time and the corresponding structural and stratigraphic record as imaged in seismic reflection records both over continental crust of Galicia Bank and over the Newfoundland and Iberia TZs. Sediments of this age in seismic sequence 4 off Iberia and sequence A off Newfoundland (Fig. 4b) are mostly horizontal, and they rarely are faulted or show splayed reflec- tions that we would expect if they were deposited over rotating fault blocks during extension (Figs 5-15). ...
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... below the U reflection (Aptian event) is poorly imaged because of the strong reflectivity of U, because of low impedance contrasts, or both. Short sections of high-amplitude reflections near the level of U probably are diabase sills, similar to those drilled at this stratigraphic level at ODP Site 1276 in the northern part of the basin (see Fig. ...
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... significant change in crustal thickness from the outer limit of continental crust (Fig. 2) seaward to the end of the refraction profile on approximately 114 Ma crust (Fig. 4g, section N2). Although Van Avendonk et al. (2006) interpreted most of this as thin oceanic crust, the recovery of peridotite basement at ODP Site 1277 seaward of anomaly M1 (Fig. 10) suggests that the basement may be domi- nantly exhumed mantle. A similar conclusion might be drawn for the Iberia side, where peridotite basement was drilled at ODP Site 1070 near anomaly M2 (open circle at youngest peridotite ridge: Fig. 4g, section I2) (Whitmarsh & Wallace ...
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... by several notable features in reflection profiles. Normally they are relatively flat-lying and their internal reflections are parallel to subparallel (Figs 5, 6, 8 & 9). Where reflections diverge, their spacing usually increases toward basin centres rather than towards footwall fault blocks. Faulting and rotation of the sequences (e.g. Fig. 10) are not common but are observed in scattered locations, including the eastern margin of Galicia Bank (PérezGussinyé et al. 2003). Thus, most basins accumu- lated sediments in the absence of obvious ...
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... sequence 4 fills valleys between peridotite ridges on the Iberia margin, its reflectivity appears to be related to the basement composition. The rounded shape of peridotite ridge crests, as well as possible slumps and debris slides (Figs 12 & 14), suggests that the serpentinite was weak and mobile. In fact, drilling of peridotite ridges within the rift has consistently recovered serpentinite breccias and olis- tostromes that reflect mass wasting of the serpenti- nized basement (Whitmarsh et al. 1998;Tucholke et al. 2004). ...
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... other cases, mass wasting from both peridotite ridges and continental fault blocks is demonstrated by chaotic fill (Figs 7b & 12) and by instances where sequence 4 laps high onto the bounding fault blocks (Figs 6b & 8c). Where cored at ODP Sites 897 and 899 (see Fig. 12a), these materials are serpentine-rich olistostromes and breccias that were emplaced before faulting and uplift of the underlying peridotite ridges ( Comas et al. 1996;Gibson et al. 1996). ...
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... other cases, mass wasting from both peridotite ridges and continental fault blocks is demonstrated by chaotic fill (Figs 7b & 12) and by instances where sequence 4 laps high onto the bounding fault blocks (Figs 6b & 8c). Where cored at ODP Sites 897 and 899 (see Fig. 12a), these materials are serpentine-rich olistostromes and breccias that were emplaced before faulting and uplift of the underlying peridotite ridges ( Comas et al. 1996;Gibson et al. 1996). Thus, some ridge-flank deposits identified in reflection profiles may predate exten- sion (e.g. Fig. 12b, right-hand side), although thickening of ...
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... 6b & 8c). Where cored at ODP Sites 897 and 899 (see Fig. 12a), these materials are serpentine-rich olistostromes and breccias that were emplaced before faulting and uplift of the underlying peridotite ridges ( Comas et al. 1996;Gibson et al. 1996). Thus, some ridge-flank deposits identified in reflection profiles may predate exten- sion (e.g. Fig. 12b, right-hand side), although thickening of the deposits in valleys shows that mass wasting also occurred during or after the fault- ing. Elsewhere, the ridge-flank deposits clearly were emplaced following extension, and their configur- ation shows that they were derived largely from the local topography (Figs 6b & ...
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... above patterns are not well defined in sequence A in the Newfoundland Basin, although rounding of presumed serpentinite ridges and poss- ible displacement of allochthonous blocks and debris are observed (Figs 10a & 13). Tucholke et al. (1989) observed rare instances where the Aptian event (U reflection) at the top of the sequence appears to truncate basement topography. ...
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... et al. (1989) observed rare instances where the Aptian event (U reflection) at the top of the sequence appears to truncate basement topography. A similar possible occurrence is shown on the left of Figure 13b. If these basement highs consisted of exceptionally weak serpentinite, it is conceivable that their exposed tops were eroded away by mass wasting or even by passing turbidity currents. ...
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... is masked ( Figs 11 & 15). Either the impedance of sequence A is so high that signal penetration is limited, the impe- dance contrast with basement is small (e.g. the shallow basement is strongly serpentinized), or both. In the northern part of the basin the masking is reduced, although deeper structure often is still difficult to detect (Fig. 10a). A major unconformity was eroded across the southern Grand Banks during the Early Cretaceous in response to deformation and doming associated with the Avalon uplift (e.g. Grant et al. 1988), and it is likely that coarse clastics shed from this region help to account for the strong reflectivity in at least the central to southern New- ...
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... et al. 1988), and it is likely that coarse clastics shed from this region help to account for the strong reflectivity in at least the central to southern New- foundland Basin. Off Iberia the Aptian event (orange reflection) is locally strong, but it generally has lower amplitude than off Newfoundland and it seldom masks underlying structure except where debris has been shed from peridotite ridges (Figs 6a & 14). ...
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... sequences 3 and B characteristically lap unconformably onto underlying sequences 4 and A, respectively (Figs 5-8 & 12 -15). This implies either a tectonic event or a sharp change in sedimen- tation pattern, or both, at the Aptian -Albian boundary. ...
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... A, late Aptian (Fig. 16a). Up to this time, sea floor was being emplaced primarily by exhumation of subcontinental mantle, and in-plane tensile stres- ses were elevated throughout the rift. The plates extended internally in local weak zones, probably where existing faults were highly serpentinized. Mass wasting and slumps contributed coarse, reflec- tive, ...
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... B, Aptian-Albian boundary (Fig. 16b). Normal sea-floor spreading began in latest Aptian -earliest Albian time. This introduction of heat and melt at the plate boundary caused in-plane tensile stress to drop sharply, resulting in a pulse of relative compression in the adjoining plates. The compression may have amplified topo- graphy in the deep basins and thus briefly ...
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... change in stress regime probably also caused differential vertical motions on the proximal continental margins, sti- mulating erosion and sediment transport to the (a) Section of ISE 10 multichannel reflection profile SW of Galicia Bank, just north of the ODP Leg 149-173 drilling transect. Location in Figure 3 (ISE 10W). Magnetic anomalies M1 and M3 are identified. ...
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... C, Albian (Fig. 16c). Following the Aptian event, relaxation of stresses reduced long- wavelength flexural topography, and sediment flux to the basins was attenuated. Slopes on basement highs also equilibrated, and there no longer was sig- nificant mass wasting from these sources. Fine- grained turbidity currents spread widely across the basins and lapped ...
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... continental crust probably soled out in serpentinized mantle, the continental faults overall were probably stronger than those in the exhumed mantle. Thus, we suggest that during Barremian-Aptian time there was very limited extension in continental crust and that most intra- plate extension occurred within areas of exhumed, serpentinized mantle (Fig. ...
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... that the period of amag- matic rifting leading to this event can be protracted if the extension rate is low and if the lithosphere is homogeneous, or if the lithosphere is heterogeneous and zones of crustal and mantle weakness are offset from one another. In the Newfoundland -Iberia rift, both the heterogeneity of the prerift Palaeozoic crust (Fig. 1) and the observed spatial and temporal shifts in the locus of rifting suggest that the latter may be the case. Reston & Phipps Morgan (2004) proposed that the onset of sea-floor spreading might be triggered by invasion of melt and heat from an adjacent rift segment or mantle plume. In the present instance, this seems unlikely because ...
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... character of the Aptian event is consistent with this postulated stress change. Relative com- pression may have amplified local basement topo- graphy and stimulated mass wasting, as suggested by chaotic deposits at the top of sequence 4 off Iberia (Figs 8c & 14b). It may also have enhanced the curvature of the Aptian-event reflection and even caused reverse faulting (Fig. 13b). ...
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... event is consistent with this postulated stress change. Relative com- pression may have amplified local basement topo- graphy and stimulated mass wasting, as suggested by chaotic deposits at the top of sequence 4 off Iberia (Figs 8c & 14b). It may also have enhanced the curvature of the Aptian-event reflection and even caused reverse faulting (Fig. 13b). Unfortu- nately, any reverse faulting that may have devel- oped on the Iberia margin has been obscured by the effects of Cenozoic compression (e.g. Fig. 12) (Boillot et al. 1979;Masson et al. ...
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... suggested by chaotic deposits at the top of sequence 4 off Iberia (Figs 8c & 14b). It may also have enhanced the curvature of the Aptian-event reflection and even caused reverse faulting (Fig. 13b). Unfortu- nately, any reverse faulting that may have devel- oped on the Iberia margin has been obscured by the effects of Cenozoic compression (e.g. Fig. 12) (Boillot et al. 1979;Masson et al. ...
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... is likely that the stress change was accompanied by long-wavelength differential verti- cal motions along the proximal margins (Fig. 16b). Numerical models indicate that release of in-plane tensile stress would cause uplift of the proximal rift basin (lower continental slope and continental rise), subsidence of the distal rift basin and the outer shelf, and uplift of the inner shelf and coastal plain (e.g. Braun & Beaumont 1989;Kooi & Cloetingh 1992). Details of ...
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... numerical models (e.g. Kooi & Cloetingh 1992) suggest that the long-wavelength vertical dis- tortion of the lithosphere caused by relative com- pression would have decayed rapidly (Fig. 16c). With the introduction of a new and relatively stable stress regime, regional flux of coarse sedi- ments in debris flows and turbidity currents would have been sharply curtailed. Slope stabilization probably also resulted in a rapid reduction of mass wasting in local basins between basement ridges on the distal margins. Thus, ...
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Citations
... A prerequisite to correctly reconstruct the Alpine Tethys and Adria Microcontinent paleogeographic evolution is to kinematically restore the present-day Atlantic margins to their pre-rift stage, to constrain the relative position of Iberia and Adria prior to their separation (Fig. 1b). Past plate kinematic reconstructions of the Iberia microplate were based on the restoration of the magnetic anomaly M0/J and did not incorporate the restoration of the up to 400 km extension accommodated by intracontinental deformation prior to the onset of seafloor spreading (Tucholke et al. 2007;Sibuet et al. 2007;Sutra et al. 2013). These restorations predicted a Late Jurassic to Aptian ocean in the Pyrenean domain that was subducted during the Albian (Sibuet et al. 2004;Vissers and Meijer 2012;van Hinsbergen et al. 2020), inconsistent with existing observations made in the Pyrenean domain (Chevrot et al. 2015). ...
In plate kinematic reconstructions, the restoration of rifted margins and their fossil equivalents exposed in orogens remains challenging. Tight fit reconstructions rely on the mapping of margins rift domains, their restoration to their pre-rift crustal thickness, and the removal of the oceanic and exhumed mantle domains. At present-day margins, high-resolution wide-angle seismic imaging allows mapping and measurement of rift domains; however, restoring fossil margins is trickier because they are largely overprinted and partially lost during convergence. Here, we present a new kinematic model for the Mesozoic rifting along the Tethys–Atlantic junction, which relies on two assumptions: (1) the width of the fossil Alpine Tethys rift domains was comparable to that of their present-day analogs, and (2) the necking zones of the former tectonic plates can be mapped, dated and used as kinematic markers. This reproducible workflow allows us, for the first time, to restore the rifted margins of the Alpine Tethys. Our reconstruction shows: (1) a westward propagation of extension through the Ionian, Alpine Tethys and Pyrenean rift systems from the Triassic to the Cretaceous, (2) the segmentation of the Mesozoic Tethyan rifted margins by strike-slip corridors, (3) the opening of an oceanic gateway at 165 Ma as mantle was exhumed along the entire Alpine Tethys and (4) the subdivision of the Mesozoic oceanic domain into compartments that were later consumed during subduction. This new model is supported by published data from the Alps, the Ionian Sea, the Pyrenees and the southern North Atlantic.
Graphical abstract
... Ma; Tucholke et al. (2007)), creating the modern southern North Atlantic Ocean (Kristoffersen, 1978;Haworth & Keen, 1979;Tucholke et al., 1989;Sibuet et al., 2012). Mesozoic rift evolution in Atlantic Canada involved a rift axis parallel to, but not coincident with, the earlier rift axis that formed the Iapetus Ocean (Williams, 1984), and a reorientation of the extension direction over time from NW-SE in the Triassic, perpendicular to Appalachian trends, to W-E during the Late Jurassic to Early Cretaceous (Tucholke et al., 1989;Grant & McAlpine, 1990), and finally to SW-NE during the Late Cretaceous (Tucholke et al., 2007) interplay between rifting processes and inherited structures contributed to the northward increase in complexity for the Atlantic Canada offshore margins, with the development of failed rift arms and the isolation of continental blocks like the Flemish Cap (Funck et al., 2003;Hopper et al., 2007;Sibuet et al., 2007b;Welford et al., 2012;Yang & Welford, 2023). ...
... Ma; Tucholke et al. (2007)), creating the modern southern North Atlantic Ocean (Kristoffersen, 1978;Haworth & Keen, 1979;Tucholke et al., 1989;Sibuet et al., 2012). Mesozoic rift evolution in Atlantic Canada involved a rift axis parallel to, but not coincident with, the earlier rift axis that formed the Iapetus Ocean (Williams, 1984), and a reorientation of the extension direction over time from NW-SE in the Triassic, perpendicular to Appalachian trends, to W-E during the Late Jurassic to Early Cretaceous (Tucholke et al., 1989;Grant & McAlpine, 1990), and finally to SW-NE during the Late Cretaceous (Tucholke et al., 2007) interplay between rifting processes and inherited structures contributed to the northward increase in complexity for the Atlantic Canada offshore margins, with the development of failed rift arms and the isolation of continental blocks like the Flemish Cap (Funck et al., 2003;Hopper et al., 2007;Sibuet et al., 2007b;Welford et al., 2012;Yang & Welford, 2023). ...
Atlantic Canada encompasses geological evidence of the orogenic and rifting episodes that inspired the development of the theory of plate tectonics and the fundamental concept of the Wilson cycle. To provide a regional crustal-scale view that can complement surface mapping studies and sparse seismological investigations, an onshore-offshore 3-D constrained gravity inversion methodology is proposed involving incorporation of topography and an inversion mesh that is laterally variable in terms of its maximum depth extent. A 3-D density anomaly model for the entirety of Atlantic Canada and its environs is generated, with the inverted density distribution structure and extracted isodensity surfaces showing excellent correspondence with independent and co-located controlled source and passive seismic constraints. The full density model and crustal thicknesses from this work are made freely available so that they may be used for further study, for instance as inputs for deformable plate reconstruction modelling.
... The WIM is the Atlantic-facing passive margin of the Iberian micro-continent. The margin is traditionally subdivided into three Break-up and seafloor spreading is considered to be diachronous along strike, with first oceanic crust forming in the Late Jurassic in the southern segment and at the Aptian-Albian boundary in the central and northern segments (Nirrengarten et al., 2017;Pereira et al., 2016;Pereira & Alves, 2012;Sibuet et al., 2004;Tucholke et al., 2007 A fourth unit, present in western Iberia but not clearly extending offshore is the Galicia-Trás-os-Montes Zone (GTMZ), a nappe stack of peri-Gondwanan units thrust over the Central Iberian Zone ...
CONTROL ID: 3961513
(1) Begoña Amigo Marx
(2) Oscar Fernandez
(3) Josep Poblet
1. Repsol, Madrid, Spain.
2. University of Vienna
3. Universidad de Oviedo, Spain.
The West Iberian Margin (WIM) is a natural laboratory for studying the evolution of riftedcontinental margins. It has been used to demonstrate and test various methods and techniques. Despite itsfrequent use as an archetypal passive margin, one of the most remarkable features of this margin is it strongalong strike variability. The details of this variability and its causes have not been thoroughly explored to date.In this study we aim to characterize the present-day three-dimensional structure and properties of the pre-riftVariscan basement, and to reconstruct the pre-rift basement structure of the margin tying it to the Variscanorogen identified onshore.
In the analysis we present here, we try to understand the distribution of Variscan basement provinces inoffshore Iberia by using integrated interpretation and modelling. The aim of this study is (i) to estimate thetectonic stretching of the margin by means of an iterative structural interpretation using 2D and 3D seismicdata, constrained by well logs and gravity data used in the construction of 2.5D gravity models across thecontinental, transitional and oceanic domains of the margin; (ii) to understand how the lithologic composition ofthe Variscan basement affected Mesozoic rifting; (iii) to correlate continental Variscan domains with thedistribution of equivalent domains in the Western Iberian Margin; and (iv) to provide insights into the causesthat may explain the along strike variability in the present day structure of the margin.
The correlation between the Variscan domains onshore and the basement under the WIM highlights theimportance of structural inheritance. We measure extension from the proximal to the distal margin, restoredoffshore domains to the undeformed state, and analyzed how basement lithology controlled the developmentof three distinct margin geometries that we have identified in the WIM. We provide an estimate of the amountof extension of the margin and how it partitioned into the upper and lower crust (which deformed ductilely) andhow these balances with overall crust extension. This study proposes a correlation of onshore and offshorebasement domains that highlights the relevance of structural inheritance in the architecture of the extensionalsystem and provides indications that can be used to account for along-strike variability in the present-daystructure of the WIM. This study also helps to understand the nature of basement on other margins dependingon rift geometry and how it affects margin thermal regime.
... Most of the volcanic rock occurrences remain poorly characterized in terms of their eruptive age, crust-mantle sources, whole-rock geochemical compositions, depositional environments, and tectonic significance. Igneous rocks generated in modern, non-plume-related rifts, such as the Newfoundland-Iberia system, provide essential information for deciphering the temporal and structural evolution of continental margins (e.g., Whitmarsh et al., 2001;Manatschal, 2004;Jagoutz et al., 2007;Tucholke et al., 2007;Keen et al., 2014) because tectonism and magmatism are linked during rifting. For example, decompression melting can be a result of lithospheric extension, and the ability to precisely date igneous rocks associated with lithospheric thinning provides temporal constraints on this process (e.g., Jagoutz et al., 2007). ...
... Peron-Pinvidic et al. (2010) discusses the possibility Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/doi/10.1130/GES02613.1/5940339/ges02613.pdf by guest of off-axis magmatism persisting for tens of millions of years after breakup caused by thermal and/or compositional perturbations (i.e., convection cells) in the mantle and variations in lithospheric thickness that arise from rifting. Some Mesozoic and younger continental margins have been studied by geophysical surveys, oceanic drilling, and oceanic floor bathymetry, which allows an in-depth understanding of continental extension through time (e.g., Tucholke et al., 2007;Peron-Pinvidic et al., 2013;Soares et al., 2012;Alves and Cunha, 2018;Zhao et al., 2021). For example, the Newfoundland (SE Grand Banks)-Iberia rift system is divided into several structural domains that run parallel to the rift axis and formed sequentially as extension migrated out toward the area of eventual breakup (Peron-Pinvidic et al., 2013). ...
The breakup of the supercontinent Rodinia and development of the western Laurentian rifted margin are in part recorded by Neoproterozoic to mid-Paleozoic igneous and sedimentary rock successions in the Canadian Cordillera. New bedrock mapping and volcanic facies analysis of Early Ordovician mafic rocks assigned to the Menzie Creek Formation in central Yukon allow reconstruction of the depositional environment during the volcanic eruptions, whole-rock geochemical data constrain the melting depth and crust-mantle source regions of the igneous rocks within the study area, and zircon U-Pb age studies provide determination of the precise timing of sub- marine eruptions. Menzie Creek Formation volcanic rocks are interlayered with continental slope strata and show lithofacies consistent with those of modern seamount systems. Representative seamount facies contain several kilometers of hyaloclastite breccia and pillow basalt with rare sedimentary rocks. Menzie Creek Formation seamounts form a linear array parallel to the Twopete fault, an ancient extensional or strike-slip fault that localized magmatism along the nascent western Laurentian margin. Zircon grains from two volcanic successions yielded high-precision chemical abrasion–thermal ionization mass spectrometry (CA-TIMS) dates of ca. 484 Ma (Tremadocian), which are interpreted as the age of eruption. Menzie Creek Formation rocks are alkali basalt and have oceanic-island basalt–like geochemical compositions. The whole-rock trace element and Nd-Hf isotope compositions are consistent with the partial melting of subcontinental lithospheric mantle at ~75–100 km depth. Post-rift, Early Ordovician seamounts in central Yukon record punctuated eruptive activity along a rift-related fault, the separation of a continental fragment from western Laurentia, or the oblique post-breakup kinematics from the counterclockwise rotation of Laurentia that facilitate local extension in the passive margin.
... The dominant structural controls on its development follow the NNE and NW trends of the Caledonian-Variscan orogenic basement formed at the end of the Palaeozoic (Wilson et al., 1989;Pastor Galán et al., 2015). The Lusitanian Basin palaeogeographic position, close to the triple junction formed by the African, Iberian and North American plates (Fernandéz, 2019), conditioned its tectono-sedimentary evolution in two main rift phases between Newfoundland Grand Banks and the Iberia margin: the Late Triassic-Middle Jurassic rift 1 and Late Jurassic-Early Cretaceous rift 2 ( Fig. 3; Tucholke et al., 2007). The influence of Tethys Ocean waters remained active during both rift phases. ...
... During the Late Triassic rift phase, continental red beds (Silves Formation) filled an extensive area of multiple half-graben basins (Pena dos Reis et al., 2017) that were eventually overlain by evaporites (Dagorda Formation) and a thick carbonate succession (Coimbra Formation, Brenha and Candeeiros groups; Wilson et al., 1989;Azerêdo, 1998;Tucholke et al., 2007;Leleu et al., 2016;Nirrengarten et al., 2017;Pena dos Reis et al., 2017). Most of the Early-Middle Jurassic was a time of relative tectonic quiescence characterising the post-rift stage with the development of a carbonate ramp depositional system (Azerêdo and Wright, 2004;Duarte et al., 2017). ...
... The Middle-Upper Jurassic disconformity marks the end of the Late Triassic-Middle Jurassic rift phase. This event is related to a very prolonged extension episode that created a hyperextended rift and, probably, the oceanic crust between conjugated basin margins that evolved to continental breakup from the Barremian to the Aptian (Alves et al., 2002;Tucholke et al., 2007;Dinis et al., 2008;Manspeizer, 2015;Nirrengarten et al., 2017;Fernandéz, 2019;Causer et al., 2020). This extension created several sub-basins filled with carbonate platform deposits (Cabaços and Montejunto formations), mixed carbonate-clastic, basinal (Abadia Formation) and continental to shallow-marine (Alcobaça Formation) deposits, overlain by continental to coastal strata (Lourinhã and Farta Pão formations ;Hill, 1988;Leinfelder and Wilson, 1998;Rasmussen et al., 1998;Alves et al., 2002;Dinis et al., 2008;Schneider and Fürsich, 2009;Mateus et al., 2013;Taylor et al., 2014). ...
Field Course in Sequence Stratigraphy (Lusitanian Basin, Portugal): cyclicity and reservoir zonation in shallow-marine setting.
... Continent-Ocean Transition (COT) is defined as a transition zone lying between the continental crust and unequivocal oceanic crust (Whitmarsh and Sawyer, 1996;Tucholke et al., 2007;Reston, 2009), which preserves key tectono-magmatic interaction from rifting to drifting at rifted margin (Peron-Pinvidic and Osmundsen, 2016;Tugend et al., 2018). The timing of the onset of decompression melting relative to the crustal thinning and magmatic budget can lead to diverse architecture and morphologies of COTs in rifted margins (Tugend et al., 2018). ...
... The amount of magmatism accompanying the extension varies dramatically at rifts and margins, with the high and low magmatic budgets corresponding to magma-rich and magma-poor rifted margins, respectively (Reston, 2009;Shillington et al., 2009;Tugend et al., 2018;Peron-Pinvidic et al., 2013;Peron-Pinvidic and Osmundsen, 2016). Magma-poor rifted margins (e.g., the Iberia-Newfoundland and Angola-Brazil conjugate margins), typified by hyper-extended continental crust and exhumed mantle, offer optimal sites for investigating lithospheric extension (e.g., Tucholke et al., 2007;Rosenbaum et al., 2008;Franke, 2013;Liu et al., 2022Liu et al., , 2023. The depth-dependent extension model predicts that the lithosphere stretches as a laminate with extension modes varying with depth because of the rheological contrasts between different layers (e.g., Reston, 2007;Beaumont, 2011, 2014). ...
... During the Mesozoic and Cenozoic, the Iberian plate occupied a key tectonic position between two evolving geodynamic contexts resulting from the relative plate motion of Africa, North America and Europe. Most of the plate reconstructions define two main kinematic phases for this tectonic setting (Fernandez, 2019;Macchiavelli et al., 2017;Schettino & Turco, 2011;Sibuet et al., 2012;Tucholke et al., 2007;Vergés & Fernàndez, 2012;Vissers & Meijer, 2012): ...
... In the first kinematic phase, Iberia experienced WNW to ENE extensional and transtensional stresses at the western and northwestern margin resulting in large rift basins (e.g. Fernandez, 2019;Péron-Pinvidic & Manatschal, 2009;Schettino & Turco, 2011;Tucholke et al., 2007). Afterwards, a complex phase of transpressional to compressional stresses was triggered by the N-S convergence, initially located along the Iberia-Europe boundary and subsequently along the Iberia-Africa boundary (e.g. ...
... The Lusitanian Basin paleogeographic position, close to the Africa, Iberia and North America triple junction (Fernandez et al., 2019), conditioned its tectonosedimentary evolution in two main rift phases separated by a regional Callovian-Oxfordian unconformity ( Figure 2): the first in the Late Triassic-Middle Jurassic (Rift phase I), and a second Late Jurassic-Early Cretaceous phase (Rift phase II) (e.g. Azerêdo et al., 2002;Tucholke et al., 2007). ...
A detailed structural analysis of the fracture network exposed in the Jurassic strata is used to reconstruct the Lusitanian Basin's brittle tectonic history related to the Meso-Cenozoic paleostress trajectories of the Iberian plate. Structural analysis is made by high-resolution virtual outcrop models and orthophoto mosaics, along with information obtained in the field. The paleostress regime is determined based on the fault-slip inversion method. Structural features are predominantly NNE-SSW, NE-SW and NW-SE-trending extensional fractures, including joints, veins, normal faults, and ~E-W-oriented strike-slip faults. These structures remained active in the early basin evolution and were repeatedly reactivated by shearing and contraction. The chronological succession and paleostress reconstruction revealed three tectonic regimes (i) NE-oriented extension, (ii) NE-oriented strike-slip and (iii) NW-shortening. The first stress regime was driven by the North Atlantic rift propagation in the Iberia's west and northwest margins in the Late Jurassic–Early Cretaceous. The younger stress states involve reactivation and inversion of pre-existing fractures by Africa–Europe convergence since the Late Cretaceous. The findings are consistent with the regional stress field which the Iberian plate has experienced since the Meso-Cenozoic.
... South of the Labrador margin, formation of the North Atlantic offshore eastern Newfoundland is marked by rifting in the latest Jurassic-Early Cretaceous (Enachescu et al., 2005), which culminated in seafloor spreading east of Orphan Basin, possibly around the Albian (Dafoe et al., 2017b;Welford et al., 2020). Similarly, south of the Orphan Basin, lithospheric breakup outboard of the Jeanne d'Arc Basin on the Grand Banks of Newfoundland occurred around the Aptian-Albian in the Newfoundland Basin (Tucholke et al., 2007). Between the Labrador margin and Orphan Basin is the Northeast Newfoundland margin, with major strike-slip offset along the Charlie-Gibbs Fracture Zone and development of a volcanic province of possible Santonian age, which may have accommodated simultaneous opening both to the south and north (Keen et al., 2014). ...
The passive margin offshore Labrador began forming during rifting in the Early Cretaceous, with seafloor
spreading starting in the Maastrichtian and ending near the Eocene–Oligocene boundary. A foundational understanding of the associated stratigraphy of this margin has been developed through previous studies of the
lithostratigraphy, biostratigraphy, and seismic stratigraphy, but the significance of clinoforms, stratal boundaries, and transgressive and regressive events has never been fully explored. In this study, we identify a series of
clinoform successions from the Late Cretaceous through Pleistocene and apply a second-order sequence stratigraphic model to refine the geological framework for the margin. We focus on the Hopedale Basin where there is
sufficient well and reflection seismic data, with substantial new seismic data collected over the last decade.
Seismic interpretation is combined with paleoenvironmental and biostratigraphic data from the wells to map
clinothem packages along the margin including: seven shoreline, five subaqueous delta, one shelf-edge, and three
shelf-edge deltas, with illustration of these on seismic profiles and paleogeographic maps representing several
time slices. Trajectory analysis of these clinothems permits the delineation of eight second-order sequences, with
systems tracts and sequence stratigraphic surfaces identified. Broader implications of our results include a revised
lithostratigraphic column for the Labrador margin. We further demonstrate regional trends during rifting and
opening in term of controlling factors on clinoform development through comparison with adjacent and conjugate margins. Tectonism dominated as a controlling factor in the Cretaceous and dwindled near the end of the
Paleocene. Eustasy and climate also influenced clinoform development in the Late Cretaceous, but became major
factors during the Cenozoic, enhancing relative sea level fall and sediment supply, with similarities to other
clinoform successions developed during Greenhouse and Icehouse conditions. Impacts to petroleum prospectivity
in the region are also discussed, and our overall seismic and stratigraphic framework provide a basis for future
study.
... Following the Caledonian-Appalachian Orogeny in the Paleozoic (Enachescu, 2006;Chenin et al., 2019), the initial NW-SE oriented rifting that eventually led to formation of the modern North Atlantic occurred during the Triassic period, creating many sedimentary basins overlying the Irish Atlantic margin (e.g., Porcupine Basin) (Štolfová and Shannon, 2009), the Galicia Bank margin (Murillas et al., 1990), and the Newfoundland margin (Enachescu et al., 2004) (Fig. 3a). Later, major W-E oriented rifting progressed northward during the Late Jurassic to Early Cretaceous periods, resulting in the separation of SE Newfoundland from the Iberia Abyssal Plain and the SE Flemish Cap from the Galicia Bank (Tucholke et al., 2007), and the opening of the Orphan Basin (Enachescu et al., 2004) (Fig. 3b). SW-NE oriented extension began in the Late Cretaceous period (de Graciansky et al., 1985), leading to continental breakup between the NE Flemish Cap-Orphan Basin region and the Goban Spur-Porcupine Bank region on the Irish Atlantic margin (Welford et al., 2012) (Fig. 3c). ...
... Overall, prior to the three main North Atlantic rifting episodes, the Orphan Knoll, Porcupine Bank, Galicia Bank, Goban Spur, and Flemish Cap collectively formed an amalgam of large, unstretched continental blocks that were sutured together during the Caledonian-Appalachian Orogeny (Fig. 3). Thereafter, several intervening failed rift basins developed between these blocks (the Jeanne d'Arc, Orphan, South Porcupine, and Rockall basins) where the complex Mesozoic extensional stress fields, coupled with inherited weaknesses, led to localized crustal hyperextension, without achieving breakup (Enachescu et al., 2004(Enachescu et al., , 2005Tucholke et al., 2007;Skogseid, 2010). ...
While the Flemish Cap played a pivotal role in the opening of the North Atlantic, the tectonic history of this continental ribbon has been poorly constrained due to insufficient seismic coverage. In this study, we present thirteen newly acquired seismic reflection profiles over the Flemish Cap, on which seismic reflectors show highly variable seismic facies both on and beneath the top acoustic basement, with exceptional imaging of layered crustal structure. The upper crust is primarily characterized by transparent, chaotic amplitude reflectivity. The lower crust, particularly on the flanks of the cap, exhibits relatively bright and coherent reflection packages interpreted as Appalachian orogenic fabrics based on onshore-offshore correlations from pre-rift plate reconstructions. Extensional systems within the continental crust of the Flemish Cap record a transitional stage between Paleozoic orogenic collapse and pre-Jurassic rifting. The crustal architecture associated with Mesozoic rifting of the Flemish Cap is also mapped and the interpreted distinct rift domains display along-strike variations. Overall, the complex tectonic history of the Flemish Cap involved dominantly ductile deformation during the Paleozoic orogenic stage, multiple deformation styles (primarily ductile and brittle-ductile) during the orogen-to-rift transitional stage, and brittle deformation during the major Jurassic-Cretaceous rifting stage.
