The post-collisional stabilization of thickened crust in the Southern Urals

Görz, Ines; Kroner, Uwe; Buschmann, Bernd

doi:10.1016/j.tecto.2008.07.007

Cited by 2 publications

(3 citation statements)

References 49 publications

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“…Further, the out‐of‐plane reflections may not be as continuous, coherent, and laterally extensive as the dipping reflection bands recognized throughout the crust in the present study. Similar steeply dipping reflections were also recognized in seismic sections from different Precambrian regions as well as the Paleozoic Urals [e.g., BABEL Working Group , 1990; Calvert et al , 1995; Goleby et al , 1989; Gorz et al , 2008]. These observations of similar reflection patterns in various regions clearly seem to justify ruling out any artifacts and substantiating them as genuine in‐plane reflections as considered in the present study.…”

Section: Modeling Results For Plausible 2‐d Velocity Structuresupporting

confidence: 86%

“…Proterozoic orogenic belts such as the trans‐Hudson orogeny, the Svekofennian orogeny, the DFB and the Paleozoic Urals evolved in island arc environments [ BABEL Working Group , 1990; Calvert et al , 1995; Vijaya Rao et al , 2000; Gorz et al , 2008]. The high‐velocity/high‐density island arc rocks of these orogens might be responsible for the preservation of collisional signatures and stabilization of the crust.…”

Section: Discussionmentioning

confidence: 99%

“…The high‐velocity/high‐density island arc rocks of these orogens might be responsible for the preservation of collisional signatures and stabilization of the crust. However, the Variscides and some other Paleozoic orogens evolved with the involvement of only continental material, i.e., without any juvenile crust derived from island arc accretion [ Gorz et al , 2008]. Thus, it can be concluded that the differences in the accretionary characteristics during the evolution of an orogeny and the associated postcollisional deformation processes could be one of the reasons for the differences in crustal structure found in different orogenic belts.…”

Section: Discussionmentioning

confidence: 99%

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Velocity modeling of a complex deep crustal structure across the Mesoproterozoic south Delhi Fold Belt, NW India, from joint interpretation of coincident seismic wide-angle and near-offset reflection data: An approach using unusual reflections in wide-angle records

Krishna

Rao

2011

J. Geophys. Res.

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[1] Seismic wide-angle record sections from favorably placed source and limited-aperture recording spreads, particularly across collision boundaries, reveal bright unusual highvelocity contrast reflections of limited lateral coherence. The arrival times of the unusual reflections for recording updip of the reflecting plane align as high apparent velocity phases at wide-angle offsets. Coincident near-offset reflection images from similar structural features provide additional control for modeling the unusual phases on the wide-angle record sections. We propose an approach for joint interpretation of these coincident seismic data sets and modeling the unusual phases on the processed wide-angle records to delineate both the velocity stratification and the geometry of the deep crustal structures consistent with the near-offset reflection images. Processed and migrated near-offset reflection images reveal several steeply dipping isolated reflections on the western margin of the south Delhi Fold Belt (DFB), NW India, interpreted as the south Delhi thrust fault. Coincident limited-aperture, wide-angle records reveal bright unusual reflections, which are also found to be associated with the same thrust fault. Observations of similar dipping reflection patterns in various other regions lend support to consider them as genuine in-plane reflections resulting from a structural fabric imprinted on horizontally oriented geological structures. We use the reflectivity structural model from the near-offset data set that provides necessary constraints for modeling and simulating the travel times and amplitudes of the unusual reflections recognized in the wide-angle records. The unusual reflections are effectively used as part of the wide-angle data set for Gaussian beam synthetic seismogram modeling, thus delineating for the first time a complex 2-D model of the seismic velocity structure of the deep crust and uppermost mantle across the Marwar Basin (MB) and the DFB. The dipping events revealed in the wide-angle data set are successfully modeled and interpreted as reflections from the thrust fault, consistent with the near-offset reflection image. The 2-D velocity model, parameterized as a stack of isolated dipping reflectors embedded in deep crustal layers, is successively refined by including the structural features recognizable both in the near-offset reflection image and in the wide-angle records. The unusual reflections are modeled as a set of discrete reflectors representing local velocity variations imprinted on the background of a deep crustal velocity structure. The lamellar structure revealed by short, isolated dipping and the subhorizontal middle to lower crustal reflections suggests heterogeneities at scale lengths on the order of at least the Fresnel zone diameter as resolved here. The local velocity variations in the deep crust can be considered analogous, on a different scale, to the models in which velocity heterogeneities on scale lengths of the seismic wavelength constitute a medium of random distribution of sc...

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Section: Modeling Results For Plausible 2‐d Velocity Structuresupporting

confidence: 86%