Geophysical studies of the structure of the Appalachian orogen in the Atlantic borderlands of Canada

Hall, Jérémy; Marillier, F.; Dehler, Sonya A.

doi:10.1139/cjes-35-11-1205

Cited by 17 publications

(33 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4) (Hall et al 1998;Funck et al 2003). Rock samples from the cap are primarily granodiorites and granites (King et al 1985) and the crust onshore has whole-crust bulk Poisson's ratios of 0.23-0.24, indicating that quartzo-feldspathic rocks dominate the crustal composition (Hughes et al 1994;Hall et al 1998).…”

Section: Initial Condition and Crustal Thinningmentioning

confidence: 99%

Structure of the Flemish Cap margin, Newfoundland: insights into mantle and crustal processes during continental breakup

Hopper

Funck

Tucholke

2007

View full text Add to dashboard Cite

Seismic reflection and refraction data from the Flemish Cap margin off Newfoundland reveal the large-scale structure of a magma-starved rifted margin. There is little evidence for significant extensional deformation of the Flemish Cap, consistent with the hypothesis that it behaved as a microplate throughout the Mesozoic. The seismic data highlight important asymmetries at a variety of scales that developed during the final stages of continental breakup and the onset of oceanic sea-floor spreading. In strong contrast to the conjugate Galicia Bank margin, Flemish Cap shows: (1) an abrupt necking profile in continental crust, thinning from 30 km thick to 3 km thick over a distance of 80 km, and a narrow, less than 20 km-wide, zone of extremely thin continental crust; (2) no clear evidence for horizontal detachment structures beneath continental crust similar to the 'S' reflection; and (3) evidence for at least a 60 km-wide zone of anomalously thin oceanic crust that began accreting to the margin shortly after continental crustal separation. The oceanic crust averages only 3 -4 km thick and in places is as thin as 1.3 km thick, although seismic layer 3 is missing where this occurs. The data suggest that there are large spatial and temporal variations in the available melt supply following continental breakup as oceanic sea-floor spreading becomes established. In addition, wide-angle data show that anomalously slow mantle P-wave velocities appear approximately where continental crust has thinned to 6-8 km thick, indicating that low-degree serpentinization begins where the entire crust has become embrittled.

show abstract

Section: Initial Condition and Crustal Thinningmentioning

confidence: 99%

Structure of the Flemish Cap margin, Newfoundland: insights into mantle and crustal processes during continental breakup

Hopper

Funck

Tucholke

2007

View full text Add to dashboard Cite

show abstract

“…Thick dashed line indicates boundary (suture) between Laurentia and Gondwana and thin dashed line indicates schematic lower limit of tectonic zones (e.g., Gander) (Quinlan et al, 1992). Note that possible discontinuity might exist at roughly 4-5 s based on changing dipping re×ector fabrics (Hall et al, 1998). B: Eastern portion of migrated section of Lithoprobe proµle LE-9 in eastern Newfoundland (see Fig.…”

Section: British Caledonidesmentioning

confidence: 99%

“…4A) and the adjacent offshore seems anomalous compared to the U.S. Appalachians because no décollement is observed, but only steep re×ector fabrics representing Taconian (Quinlan et al, 1992) deformation. Hall et al (1998) suggested that an interpreted discontinuity between upper and lower crustal dipping re×ectors implies a mid-crustal rheological detachment; however, no horizontal re×ection sequence analogous to the Appalachian décollement is observed.…”

Section: Thin-skinned Versus Thick-skinned Deformation Regimesmentioning

confidence: 99%

“…Several thousand kilometers of deep seismic re×ection proµles, acquired both onland and offshore, show pronounced re×ectivity throughout the crust and across many parts of the orogen (Quinlan et al, 1992). The re×ection data from central Newfoundland provide probably the highest quality proµles across the Appalachians in North America (Hall and Quinlan, 1994;Hall et al, 1998).…”

mentioning

confidence: 98%

See 1 more Smart Citation

Review of seismic reflector signatures of crustal deformation in the Appalachian-Caledonide orogen with reference to the Spanish Variscides and the Uralides

McBride¹,

Knapp²

2002

Variscan-Appalachian Dynamics: The Building of the Late Paleozoic Basement

View full text Add to dashboard Cite

After the µrst images of the crustal structure of the southern Appalachians appeared on seismic re×ection proµles in the 1970s (Cook et al., 1979), thousands of kilometers of deep seismic data were acquired over the greater Appalachian-Caledonide-Variscan orogen on both sides ABSTRACT The availability of thousands of kilometers of deep seismic re×ection proµles from the Paleozoic orogenic belts around the North Atlantic Ocean provides an unparalleled opportunity to synthesize the contrasts and similarities of crustal deformation fabrics of compressional orogens. Dominating re×ector fabrics are (1) shallow crustal sequences of subhorizontal re×ections (décollement levels) that abruptly merge with complex dipping zones (sutures or root zones), (2) broad antiformal re×ector patterns, in places underlain by a dipping planar re×ector and interpreted as asymmetric folding and shearing in the deep crust, (3) complex, subhorizontal re×ectors in the middle to lower crust that can be explained in places as intense ductile shearing related to terrane accretion and continental convergence, and (4) zones of deeply penetrating and mostly planar dipping features, interpreted as reverse-sense brittle faults or ductile shear zones. The structure of re×ectors nearer the Moho discontinuity is more complex and variable relative to planar re×ectors higher in the crust. Re×ectors that curve into the Moho seem to typify orogens where the synorogenic lowermost crust is preserved and imply that the Moho acted as a décollement. In contrast, cases where dipping planar re×ectors are abruptly cut off by a ×at Moho suggest a postorogenic process that has destroyed and reequilibrated lowermost crustal structure. Other variations between the diverse re×ector fabrics can in part be understood (and predicted) in terms of variations between thin-and thick-skinned deformation regimes, which are usually not viewed simultaneously on any one proµle or group of proµles. More recently acquired deep seismic proµles from the Spanish Variscides and the Uralides provide examples of convergent belts where most of the full crustal orogenic structure has been preserved intact. These may serve as analogs for less well preserved or evolving orogenic belts.

show abstract

“…Seismic profiles north of the Strait of Canso indicate continuous bedding reflections across the inferred location of the Canso fault and no geophysical evidence to support the extension of the Canso fault from north of Prince Edward Island to mainland Nova Scotia in Carboniferous rocks in the offshore (Durling et al 1995). Based on Lithoprobe line 86-1, Hall et al (1998) inferred an unresolved difficulty linking Appalachian crustal structures observed in Cape Breton Island and New Brunswick, and suggested that offset of late Paleozoic deformation zones may be indicative of a pullapart origin for late Paleozoic extension localized by the earlier Canso transform fault (Stockmal et al 1990).…”

Section: Southern Gulf Of St Lawrencementioning

confidence: 98%

Geophysical modeling of Devonian plutons in the southern Gulf of St. Lawrence: implications for Appalachian terrane boundaries in Maritime Canada

2007

View full text Add to dashboard Cite

A prominent positive magnetic anomaly spans the 100 km distance between Prince Edward Island and Cape Breton Island in the southern Gulf of St. Lawrence. The anomaly occurs in an area of complex structure where Appalachian terrane boundaries are poorly resolved because of thick late Paleozoic sedimentary cover. Analysis of the magnetic anomaly led to the interpretation that it is produced by four separate, approximately circular, source bodies aligned along the northwesterly trend of the anomaly. Seismic data, physical property measurements, and magnetic and gravity anomalies were used to further investigate the anomaly sources through forward modeling techniques. The four source bodies have densities and magnetic susceptibilities compatible with dioritic to granitic compositions. Modeling also suggests that basement to the north of the plutons has higher density and susceptibility than basement to the south, and hence the source bodies are interpreted as plutons emplaced along the boundary between Ganderian composite terranes to the north and the Ganderian Brookville -Bras d'Or terrane to the south. This interpretation suggests that the Ganderia-Avalonia boundary is located farther south, and shows the need for re-evaluation of the location and role of the Canso fault in offsetting terranes between Cape Breton Island and southern New Brunswick.Résumé : Une anomalie magnétique positive marquée recouvre la distance de 100 km entre l'Île-du-Prince-Édouard et l'île du Cap-Breton dans le sud du golfe du Saint-Laurent. L'anomalie se retrouve dans un secteur de structures complexes où les limites du terrane appalachien sont mal définies en raison de l'épaisse couverture sédimentaire du Paléozoïque tardif. L'analyse de l'anomalie magnétique a conduit à l'interprétation qu'elle est produite par quatre amas sources séparés, de forme approximativement circulaire, alignés le long de la tendance nord-ouest de l'anomalie. Les données sismiques, les mesures des propriétés physiques et les anomalies magnétiques et gravimétriques ont été utilisées pour étudier plus en détails les sources de l'anomalie par des techniques de modélisation progressive. Les quatre amas sources ont des densités et des susceptibilités magnétiques compatibles avec des compositions dioritiques à granitiques. Selon la modélisation, le socle au nord des plutons aurait une densité et une susceptibilité plus élevées que le socle vers le sud; les amas sources sont donc interprétés comme des plutons mis en place le long de la limite entre les terranes composites de Ganderia, au nord, et le terrane Brookville -Bras d'Or de Ganderia, au sud. Selon cette interprétation, la limite Ganderia-Avalonia serait située plus au sud et elle signale le besoin de réévaluer l'emplacement et le rôle de la faille Canso dans le décalage des terranes entre l'île du Cap-Breton et le sud du Nouveau-Brunswick.[Traduit par la Rédaction] Cook et al. 1565

show abstract

Geophysical studies of the structure of the Appalachian orogen in the Atlantic borderlands of Canada

Cited by 17 publications

References 0 publications

Structure of the Flemish Cap margin, Newfoundland: insights into mantle and crustal processes during continental breakup

Structure of the Flemish Cap margin, Newfoundland: insights into mantle and crustal processes during continental breakup

Review of seismic reflector signatures of crustal deformation in the Appalachian-Caledonide orogen with reference to the Spanish Variscides and the Uralides

Geophysical modeling of Devonian plutons in the southern Gulf of St. Lawrence: implications for Appalachian terrane boundaries in Maritime Canada

Contact Info

Product

Resources

About