Reflection‐diffraction seismic pattern at crustal suture zones

Sadowiak, P.; Wever, Th.

doi:10.1029/tc009i006p01495

Cited by 18 publications

(6 citation statements)

References 31 publications

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“…2E). The pattern of antiformal re×ectors underlain by quasiplanar re×ectors is similar to geological patterns mapped at the surface in compressional orogens, especially suture zones (Sadowiak and Wever, 1990;McBride and Nelson, 1991;Blundell, 1993;McBride and England, 1999). In the southern Appalachians, this pattern is overwhelmingly univergent (i.e., verging northwest, toward the continent).…”

Section: North American Appalachianssupporting

confidence: 69%

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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

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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.

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Section: North American Appalachianssupporting

confidence: 69%

“…2B). Sadowiak and Wever (1990) recognized such close associations of dipping re×ections and diffractions as typical of suture zones. Along a key deep re×ection transect in western Georgia (Figs.…”

Section: North American Appalachiansmentioning

confidence: 94%

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

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“…Even though the migrated section has been affected by artifacts due to smiles in some places, it is presented here since we observe a clear image of the Moho in the time‐migrated section. Diffraction‐like events are the key features of suture zones observed in seismic sections from different parts of the globe [ Sadowiak and Wever , ]. Final interpretation is based on the seismic stack and poststack migrated sections derived in the present study.…”

Section: Resultsmentioning

confidence: 81%

New seismic images of the Central Indian Suture Zone and their tectonic implications

2013

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[1] The Central Indian Suture (CIS), a mega shear zone, located in the central part of the Indian shield exhibits a complex structure with compositional heterogeneity. Multifold deep seismic reflection data acquired across the shear zone have been previously processed using the conventional common midpoint (CMP) method. In this study, we show results from imaging this shear zone using the common reflection surface (CRS) stack method, an alternative to the CMP stack. Our new images reveal geological features that are either poorly resolved or entirely absent in the earlier CMP stack section. Our major findings include a well-imaged Moho throughout the study area, existence of different crustal blocks each with distinct dipping reflection fabrics on the northern and southern sides of the CIS, a well-defined 8 km of Moho offset beneath the CIS, and a high-amplitude reflective zone representing the CIS. The Moho located at a depth of 48 km in the Bastar craton, to the south of the CIS, is also clearly resolved in our CRS stack, as well as in the time-migrated section. A deeply penetrating crustal-scale imbricated structure imaged up to a depth of 16.0 s two-way time (TWT), to the south of the CIS, suggests that the Bastar craton is subducting toward north. An oppositely dipping reflection fabric, a Moho offset, a positive-negative gravity anomaly pair, and the geological data indicate that the CIS represents a collision zone developed due to the interaction of the Bastar and Bundelkhand cratons with the evolution of the Sausar orogeny at~1000 Ma. This orogeny is contemporaneous with the Grenvillian orogeny and Rodinia assembly. Another thrust fault extending from 4 to 14 s TWT observed to the north of the CIS may represent the earlier, pre-Sausar orogenic activity at 1.6-1.5 Ga. The available seismic characteristics suggest that the CIS, the collisional suture, is also likely to represent a strike-slip fault.

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“…5b). On a more global scale Sadowiak and Wever (1990) have studied the various diffraction phenomena along deep faults. A major problem regarding the much debated depth extent of terranes has been solved by this study, at least for the continental terrane of the Varisades.…”

mentioning

confidence: 75%

“…2.4 Appearance of diffraction dusters in the middle and lower crust, at the bottom of inclined reflections (faults) in the upper crust (Sadowiak and Wever, 1990).…”

Section: Introductionmentioning

confidence: 99%

The terrane concept and its manifestation by deep reflection studies in the Variscides

Meißner¹,

Sadowiak²

1992

Terra Nova

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SUMMARY The terrane concept is understood as an important extension of plate tectonics and is based on the recognition of allochthonous, mobile geological units. The concept is successfully applied to the Variscides with their wide range of collisional belts. It is mainly supported by the dense deep‐seismic network of DEKORP, which reveals certain reflectivity patterns and succeeds in mapping old and new deep fault zones between the terranes. Variscan terranes are rooted in the ductile lower crust and seem to consist of continental crust only, partly exclusively of rigid upper crust. Oceanic terranes, on the other hand, are always rooted in the asthenosphere. The development of continental terranes and their boundaries depends strongly on their thermal and rheological history. In the case of post‐orogenic collapse with heating and extension of the lower crust, seismic lamellae develop and often truncate former thrust faults.

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Reflection‐diffraction seismic pattern at crustal suture zones

Cited by 18 publications

References 31 publications

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

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

New seismic images of the Central Indian Suture Zone and their tectonic implications

The terrane concept and its manifestation by deep reflection studies in the Variscides

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