Crustal structure and kinematic framework of the northwestern Pontiac Subprovince, Quebec: an integrated structural and geophysical study

1994 ◽  
Vol 31 (2) ◽  
pp. 271-281 ◽  
Author(s):  
Keith Benn ◽  
Warner Miles ◽  
Mohammad R. Ghassemi ◽  
John Gillett
Keyword(s):  
Crustal Structure ◽  
Shear Zones ◽  
Seismic Profile ◽  
Crustal Thickening ◽  
Structural Development ◽  
Seismic Reflection Profile ◽  
Gravity And Magnetic ◽  
Magnetic Model ◽  
Geophysical Study ◽  
Magnetic Modelling

Structural mapping, gravity and magnetic modelling, and interpretation of a deep-seismic profile in the northwestern Pontiac Subprovince outline the crustal structure and early structural development of the region. Penetrative D1 fabrics in the Pontiac Group and in the underlying Opasatica Gneiss may record south-vergent thrusting of a high-grade nappe. D2 and D3 structures record southeast-vergent folding and thrusting within the Pontiac Group. Steeply dipping northeast-trending ductile shear zones may represent oblique ramps initiated during D1. Gravity and magnetic model profiles are consistent with north-dipping structures in the shallow crust, and indicate that the Pontiac Group is a wedge underlain by north-dipping slabs of different densities and magnetic susceptibilities. Interpretation of a seismic reflection profile shows mid-crustal duplex structures overlying a deeper thrust between 16 and 24 km. From the surface to the deep crust, the structure of the northwestern Pontiac Subprovince records south- to southeast-directed thrusting and important crustal thickening during a collisional event. In light of field observations, available isotopic ages suggest that D1 deformation began no earlier than 2694 Ma, and that deformation continued until at least 2668 Ma.

Crustal structure beneath the Western Canada Sedimentary Basin: constraints from gravity and magnetic modelling

2002 ◽  
Vol 39 (3) ◽  
pp. 291-312 ◽  
Author(s):  
Jacqueline Hope ◽  
David Eaton
Keyword(s):  
Magnetic Anomaly ◽  
Crustal Structure ◽  
Potential Field ◽  
Red Deer ◽  
Sedimentary Basin ◽  
Western Canada ◽  
Western Canada Sedimentary Basin ◽  
Gravity And Magnetic ◽  
Magnetic Modelling ◽  
Canada Sedimentary Basin

Regional gravity and magnetic anomalies that originate from crystalline basement rocks extend over many parts of the Western Canada Sedimentary Basin. Although these potential-field anomalies provide a basis for tectonic subdivisions of the basement crust, most previous interpretations of these features have been largely qualitative in nature. This study focuses on numerical simulation and quantitative interpretation of five regional potential-field anomalies in Alberta, Canada, for which independent constraints on crustal structure are available from Lithoprobe seismic and electromagnetic studies. The Kimiwan High (~55°N, 116°W) is a roughly 250 km long linear magnetic high. Seismic profiles across this anomaly provide evidence for a crustal-scale extensional fault system that offsets the Winagami reflection sequence, a series of mid-crustal sills. We find that the magnetic anomaly can be modelled as either a 15–40 km wide zone of moderate positive susceptibility (4.5 × 10–3 SI units) in the hanging wall of the detachment (5–17 km depth), or as a narrower (5–10 km), steeply dipping zone of high susceptibility (2.5 × 10–2 SI units) in the footwall (16–32 km depth). We interpret the former scenario as indicative of an extensive zone of alteration above the fault, whereas the latter could represent a decapitated granitic pluton that correlates with magmatic rocks farther north. To the southeast, the Thorsby Low (~53°N, 114°W) is a sinuous, 400 km long magnetic low and gravity gradient trend that appears to be a splay of the much more extensive Snowbird tectonic zone. Previous seismic interpretations across the Thorsby Low indicate that it coincides with a 10 km offset in the Moho. Our results show that this abrupt change in crustal thickness is consistent with, but not required by, the gravity signature of this feature. The northeast-striking Red Deer High (~53°N, 112°W) is a narrow magnetic anomaly in central Alberta with variable intensity along strike. Previous magnetotelluric studies suggest that the Red Deer anomaly is closely associated with a linear, highly conductive body in the upper basement. Our modelling results confirm the shallow depth of the causative body and suggest an eastward dip that is consistent with published seismic interpretations. Near the eastern border of Alberta, the 300 km long Eyehill High (~52°N, 110°W) is a prominent north-striking magnetic anomaly adjacent to the western hinterland of the Trans-Hudson Orogen. Combined gravity and magnetic modelling show that this feature occurs near the western boundary of a large block of dense material in the lower crust. The magnetic anomaly can be simulated by a near-vertical dyke-like body in the upper crust. Lastly, the Vulcan structure (~50.5°N, 112°W) forms the ~400 km long, northern boundary of the Archean Medicine Hat block. It is defined by a sinuous east-trending magnetic anomaly and gravity low. The wavelength and polarity of the magnetic anomaly (positive in the north), coupled with the coincident gravity low, are most simply explained by a mid-crustal low-density body with significant remanent magnetization oriented antiparallel to the present-day field.

scholarly journals Gravity and Magnetic Constraints on the Crustal Structure and Evolution of the Horeki Seamount in the Izu-Bonin Arc

2006 ◽  
Vol 4 (0) ◽  
pp. 55-65 ◽  
Author(s):  
Toshiya Fujiwara ◽  
Yukari Kido ◽  
Yoshihiko Tamura ◽  
Osamu Ishizuka
Keyword(s):  
Crustal Structure ◽  
Gravity And Magnetic

scholarly journals SEISMIC FACIES ANALYSIS ON 2D SEISMIC REFLECTION PROFILE IN BARUNA AND JAYA LINE AT NORTH EAST JAVA BASIN

2016 ◽  
Vol 9 (1) ◽  
pp. 15
Author(s):  
Taufan Wiguna ◽  
Rahadian Rahadian ◽  
Sri Ardhyastuti ◽  
Safira Rahmah ◽  
Tati Zera
Keyword(s):  
Facies Analysis ◽  
Seismic Profile ◽  
Seismic Facies ◽  
Seismic Reflection Profile ◽  
Reef Facies ◽  
North East ◽  
Time Migration ◽  
Seismic Facies Analysis ◽  
External Form ◽  
Seismic Reflector

<p class="abstrak">Two dimension (2D) seismic profile of Baruna and Jaya lines at North-East Java Basin show seismic reflector characteristics that can be used to interpret sediment thickness and continuity. Those reflector characteristics that can be applied for seismic facies analysis that represent depositional environment. This study starts from seismic data processing that using Kirchhoff Post Stack Time Migration method which is 2D seismic profile as result. Seismic reflector characterization has been done to both 2D profiles. Seismic reflector characterization was grouped as (i) individual reflection, (ii) reflection  configuration, (iii) reflection termination, (iv) external form. Individual reflection characteristics show high and medium amplitude, medium and low frequency, and continuous. Configuration reflection is continuous with parallel and subparallel type. Reflection termination shows onlap, and external form shows sheet drape. Local mound appearance can be interpreted as paleo-reef. Facies seismic anlysis result for this study area is shelf.</p>

scholarly journals Cretaceous-Paleocene Evolution and Crustal Structure of the Northern Vøring Margin (Offshore Mid-Norway): Results from Integrated Geological and Geophysical Study

Tectonics ◽  
2018 ◽  
Vol 37 (2) ◽  
pp. 497-528 ◽  
Author(s):  
D. Zastrozhnov ◽  
L. Gernigon ◽  
I. Gogin ◽  
M. M. Abdelmalak ◽  
S. Planke ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Geophysical Study
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