Three crustal zones in the Thor–Odin – Pinnacles area, southern Omineca Belt, British Columbia

1991 ◽  
Vol 28 (12) ◽  
pp. 2003-2023 ◽  
Author(s):  
Sharon D. Carr
Keyword(s):  
Late Cretaceous ◽  
Hanging Wall ◽  
Thermal Quenching ◽  
Shear Zones ◽  
Normal Faults ◽  
Substantial Part ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Early Tertiary ◽  
Late Paleocene

The present crustal architecture of the southern Omineca Belt in the Canadian Cordillera is a product of Eocene extension and crustal thinning superimposed on a crust that was thickened and deformed during Paleozoic and Jurassic to Late Paleocene compression. Amphibolite-facies rocks exposed as gneiss complexes within the Shuswap Metamorphic Complex, in the southern Omineca Belt, were buried during compression and were exhumed in the lower plates of low- to moderate-angle plastic–brittle Eocene extensional faults.In the Thor–Odin – Pinnacles area three crustal zones, which have experienced different deformation and thermal histories, and intervening shear zones can be correlated with Lithoprobe seismic reflection data. The Basement Zone, which comprises crystalline basement and overlying supracrustal gneisses, is bounded above by the Monashee décollement, a deep-seated northeasterly directed Mesozoic–Paleocene thrust fault. In the hanging wall of the décollement, polydeformed gneisses and schists of the Middle Crustal Zone are characterized by Late Cretaceous–early Tertiary ductile strain, plutonism, and thermal quenching. They are bounded at the top by crustal-scale Eocene normal faults that juxtapose Upper Crustal Zone rocks characterized by Jurassic and older structures and a Jura-Cretaceous cooling history.Middle Crustal Zone rocks of the Thor–Odin – Pinnacles area are correlative with part of the Late Proterozoic Horsethief Creek Group and Cambrian to Jurassic strata and host extensive plutons, stocks, and sheets of the syntectonic and posttectonic Late Paleocene – Early Eocene Ladybird granite suite. Field mapping and geochronology indicate that (i) a substantial part of the penetrative compressional polydeformation history and the thermal peak of metamorphism within the Middle Crustal Zone occurred in the Late Cretaceous–Paleocene; (ii) thrusting on the Monashee décollement had ended by 58 Ma; (iii) the onset of extensional deformation either overlapped or closely followed the compressional regime; (iv) Middle Crustal Zone metamorphic and igneous rocks were hot in the Paleocene and cooled rapidly in the early Tertiary because of extensional denudation.

Basement-involved inversion at the Appalachian structural front, western Newfoundland: an interpretation of seismic reflection data with implications for petroleum prospectivity

2004 ◽  
Vol 52 (3) ◽  
pp. 215-233 ◽  
Author(s):  
Glen S. Stockmal ◽  
Art Slingsby ◽  
John W.F. Waldron
Keyword(s):  
Seismic Reflection ◽  
Hanging Wall ◽  
Normal Fault ◽  
Hydrocarbon Exploration ◽  
Normal Faults ◽  
Apparent Magnitude ◽  
Seismic Reflection Data ◽  
The Public ◽  
Reflection Data ◽  
New Interpretation

Abstract Recent hydrocarbon exploration in western Newfoundland has resulted in six new wells in the Port au Port Peninsula area. Port au Port No.1, drilled in 1994/95, penetrated the Cambro-Ordovician platform and underlying Grenville basement in the hanging wall of the southeast-dipping Round Head Thrust, terminated in the platform succession in the footwall of this basement-involved inversion structure, and discovered the Garden Hill petroleum pool. The most recent well, Shoal Point K-39, was drilled in 1999 to test a model in which the Round Head Thrust loses reverse displacement to the northeast, eventually becoming a normal fault. This model hinged on an interpretation of a seismic reflection survey acquired in 1996 in Port au Port Bay. This survey is now in the public domain. In our interpretation of these data, the Round Head Thrust is associated with another basement-involved feature, the northwest-dipping Piccadilly Bay Fault, which is mapped on Port au Port Peninsula. Active as normal faults in the Taconian foreland, both these faults were later inverted during Acadian orogenesis. The present reverse offset on the Piccadilly Bay Fault was previously interpreted as normal offset on the southeast-dipping Round Head Thrust. Our new interpretation is consistent with mapping on Port au Port Peninsula and north of Stephenville, where all basement-involved faults are inverted and display reverse senses of motion. It also explains spatially restricted, enigmatic reflections adjacent to the faults as carbonate conglomerates of the Cape Cormorant Formation or Daniel’s Harbour Member, units associated with inverted thick-skinned faults. The K-39 well, which targeted the footwall of the Round Head Thrust, actually penetrated the hanging wall of the Piccadilly Bay Fault. This distinction is important because the reservoir model invoked for this play involved preferential karstification and subsequent dolomitization in the footwalls of inverted thick-skinned faults. The apparent magnitude of structural inversion across the Piccadilly Bay Fault suggests other possible structural plays to the northeast of K-39.

The southern Omineca Belt, British Columbia: new perspectives from the Lithoprobe Geoscience Program

1995 ◽  
Vol 32 (10) ◽  
pp. 1720-1739 ◽  
Author(s):  
Sharon D. Carr
Keyword(s):  
Late Cretaceous ◽  
Seismic Reflection ◽  
Shear Zones ◽  
Crustal Thickening ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Basement Rocks ◽  
Peraluminous Granites ◽  
Surface Geology ◽  
Lower Crustal

Geological, isotopic, and geochronology studies carried out by university and government researchers, concurrently with the Lithoprobe program, have greatly refined our understanding of the regional geology, crustal structure, and tectonics of the Omineca Belt. Sound correlations have been established between surface geology and seismic reflection data. Cretaceous–Eocene thrust faults that are imaged in the subsurface in the Shuswap complex may be part of a break-forward thrust system that feeds into the Purcell Anticlinorium and the Foreland Belt. The Monashee décollement is the western continuation of the sole thrust beneath the Foreland Belt and provides a means of linking shortening across the entire orogen. The thermal peak of metamorphism in the central and southern Shuswap complex is now known to have occurred in the Late Cretaceous–Paleogene in contrast with earlier held views. North American basement rocks are now known to extend beneath the eastern half of the Canadian Cordillera. Geochronology studies have revealed Early Proterozoic and Late Cretaceous–Eocene metamorphism in basement rocks of the Monashee complex, and suggest that these rocks were located to the east of the metamorphic front throughout the Jurassic and Early Cretaceous. Anatectic peraluminous granites were produced in the Shuswap complex between 135 and 52 Ma in response to pulses of crustal thickening and heating, and in some cases served to localize Eocene extensional shear zones and to transfer extensional displacement from one shear zone to another. A flat Moho and other seismic reflection data are consistent with interpretations of lower crustal flow to balance early Tertiary extension in the upper crust. Crustal-scale extension and the Slocan Lake fault zone provided the source and setting for Ag–Pb–Zn–Au mineralization in the Nelson–Silverton area.

Application of section-balancing techniques to deep seismic reflection data from offshore eastern Canada: preliminary observations

1990 ◽  
Vol 27 (4) ◽  
pp. 494-500 ◽  
Author(s):  
M. C. Dentith ◽  
J. Hall
Keyword(s):  
Seismic Reflection ◽  
Hanging Wall ◽  
Shear Zones ◽  
Ductile Deformation ◽  
Eastern Canada ◽  
Seismic Reflection Data ◽  
Deep Seismic Reflection ◽  
Grand Banks ◽  
Jeanne D'arc Basin ◽  
Reflection Data

The application of section-balancing techniques to the analysis of deep seismic sections requires account be taken of isostasy and ductile-deformation processes. Structures imaged by deep seismic reflection profiling across the southern Grand Banks, offshore eastern Canada, are analyzed in this way. Correlations of dipping events in the deep crust, interpreted as shear zones, with faults recognized in the shallow part of the section are tested by attempting to restore the sections to their undeformed state by reversing the displacements on the faults. This process tests the geometric compatibility of the interpreted fault and the structures in its hanging wall. Our models suggest that the faults bounding the Whale and Horseshoe basins detach at the Mohorovičić discontinuity. In contrast, the fault bounding the Jeanne d'Arc Basin detaches within the lower crust.

scholarly journals Geologic transect across the Grenville orogen of Ontario and New York

2000 ◽  
Vol 37 (2-3) ◽  
pp. 193-216 ◽  
Author(s):  
S D Carr ◽  
R M Easton ◽  
R A Jamieson ◽  
N G Culshaw
Keyword(s):  
New York ◽  
Cross Sections ◽  
Shear Zones ◽  
Normal Faults ◽  
Grenville Province ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Seismic Reflectivity ◽  
Granitoid Rocks ◽  
Laurentian Margin

Revised cross sections of the western Grenville Province incorporate new geologic results and reprocessed seismic reflection data. The geology is presented in terms of three tectonic elements: (1) "pre-Grenvillian Laurentia and its margin" with ca. 1740 and 1450 Ma continental arc plutons and associated supracrustal rocks; (2) "Composite Arc Belt" of allochthonous ~1300-1250 Ma volcanic arcs and sedimentary rocks; and (3) "Frontenac-Adirondack Belt" characterized by supracrustal and granitoid rocks, and anorthosites, of uncertain affinity, that may represent a distinctive part of the Composite Arc Belt or an offshore (micro)continent. Rocks of the Composite Arc and Frontenac-Adirondack belts were amalgamated with each other by ca. 1160 Ma, were then thrust over Laurentia during ca. 1080-1035 Ma and ca. 1010-980 Ma phases of convergence, and were dissected and exhumed by <1040 Ma normal faults. Penetrative deformation was restricted to that part of the pre-Grenvillian Laurentian margin that lies to the southeast of the Grenville front and parts of the accreted Composite Arc and Frontenac-Adirondack belts. The Laurentian rocks in the Grenville Province are bounded to the northwest and southeast by southeast-dipping ductile thrust and (or) normal shear zones. The Composite Arc and Frontenac-Adirondack belts to the southeast are bounded by ductile and brittle-ductile thrust and (or) normal faults that separate domains with contrasting cooling histories. Despite a long pre-Grenvillian tectonic and plutonic history, the present crustal architecture and much of the seismic reflectivity were acquired during 1080-980 Ma phases of compression and extension.

scholarly journals Mantle-derived helium released through the Japan trench bend-faults

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jin-Oh Park ◽  
Naoto Takahata ◽  
Ehsan Jamali Hondori ◽  
Asuka Yamaguchi ◽  
Takanori Kagoshima ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Large Scale ◽  
Japan Trench ◽  
Helium Isotope ◽  
Normal Faults ◽  
Circulation System ◽  
Deep Penetration ◽  
Oceanic Plate ◽  
Seismic Reflection Data ◽  
Reflection Data

AbstractPlate bending-related normal faults (i.e. bend-faults) develop at the outer trench-slope of the oceanic plate incoming into the subduction zone. Numerous geophysical studies and numerical simulations suggest that bend-faults play a key role by providing pathways for seawater to flow into the oceanic crust and the upper mantle, thereby promoting hydration of the oceanic plate. However, deep penetration of seawater along bend-faults remains controversial because fluids that have percolated down into the mantle are difficult to detect. This report presents anomalously high helium isotope (3He/4He) ratios in sediment pore water and seismic reflection data which suggest fluid infiltration into the upper mantle and subsequent outflow through bend-faults across the outer slope of the Japan trench. The 3He/4He and 4He/20Ne ratios at sites near-trench bend-faults, which are close to the isotopic ratios of bottom seawater, are almost constant with depth, supporting local seawater inflow. Our findings provide the first reported evidence for a potentially large-scale active hydrothermal circulation system through bend-faults across the Moho (crust-mantle boundary) in and out of the oceanic lithospheric mantle.

Late Cretaceous – Cenozoic history of the transition zone between the East European Craton and the Paleozoic Platform, Polish sector of the Baltic Sea, revealed by new offshore regional seismic reflection data (BALTEC project)

2021 ◽  
Author(s):  
Piotr Krzywiec ◽  
Łukasz Słonka ◽  
Quang Nguyen ◽  
Michał Malinowski ◽  
Mateusz Kufrasa ◽  
...  
Keyword(s):  
High Resolution ◽  
Late Cretaceous ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Upper Cretaceous ◽  
Seismic Reflection Data ◽  
East European ◽  
Reflection Data ◽  
Multichannel Seismic Reflection ◽  
Multichannel Seismic Reflection Data

&lt;p&gt;In 2016, approximately 850 km of high-resolution multichannel seismic reflection data of the BALTEC survey have been acquired offshore Poland within the transition zone between the East European Craton and the Paleozoic Platform. Data processing, focused on removal of multiples, strongly overprinting geological information at shallower intervals, included SRME, TAU-P domain deconvolution, high resolution parabolic Radon demultiple and SWDM (Shallow Water De-Multiple). Entire dataset was Kirchhoff pre-stack time migrated. Additionally, legacy shallow high-resolution multichannel seismic reflection data acquired in this zone in 1997 was also used. All this data provided new information on various aspects of the Phanerozoic evolution of this area, including Late Cretaceous to Cenozoic tectonics and sedimentation. This phase of geological evolution could be until now hardly resolved by analysis of industry seismic data as, due to limited shallow seismic imaging and very strong overprint of multiples, essentially no information could have been retrieved from this data for first 200-300 m. Western part of the BALTEC dataset is located above the offshore segment of the Mid-Polish Swell (MPS) &amp;#8211; large anticlinorium formed due to inversion of the axial part of the Polish Basin. BALTEC seismic data proved that Late Cretaceous inversion of the Koszalin &amp;#8211; Chojnice fault zone located along the NE border of the MPS was thick-skinned in nature and was associated with substantial syn-inversion sedimentation. Subtle thickness variations and progressive unconformities imaged by BALTEC seismic data within the Upper Cretaceous succession in vicinity of the Kamie&amp;#324;-Adler and the Trzebiat&amp;#243;w fault zones located within the MPS documented complex interplay of Late Cretaceous basin inversion, erosion and re-deposition. Precambrian basement of the Eastern, cratonic part of the study area is overlain by Cambro-Silurian sedimentary cover. It is dissected by a system of steep, mostly reverse faults rooted in most cases in the deep basement. This fault system has been regarded so far as having been formed mostly in Paleozoic times, due to the Caledonian orogeny. As a consequence, Upper Cretaceous succession, locally present in this area, has been vaguely defined as a post-tectonic cover, locally onlapping uplifted Paleozoic blocks. New seismic data, because of its reliable imaging of the shallowest substratum, confirmed that at least some of these deeply-rooted faults were active as a reverse faults in latest Cretaceous &amp;#8211; earliest Paleogene. Consequently, it can be unequivocally proved that large offshore blocks of Silurian and older rocks presently located directly beneath the Cenozoic veneer must have been at least partly covered by the Upper Cretaceous succession; then, they were uplifted during the widespread inversion that affected most of Europe. Ensuing regional erosion might have at least partly provided sediments that formed Upper Cretaceous progradational wedges recently imaged within the onshore Baltic Basin by high-end PolandSPAN regional seismic data. New seismic data imaged also Paleogene and younger post-inversion cover. All these results prove that Late Cretaceous tectonics substantially affected large areas located much farther towards the East than previously assumed.&lt;/p&gt;&lt;p&gt;This study was funded by the Polish National Science Centre (NCN) grant no UMO-2017/27/B/ST10/02316.&lt;/p&gt;

scholarly journals Seismic reflection data reveal the 3D structure of the newly discovered Exmouth Dyke Swarm, offshore NW Australia

2020 ◽  
Author(s):  
Craig Magee ◽  
Christopher A.-L. Jackson
Keyword(s):  
Seismic Reflection ◽  
Surface Deformation ◽  
3D Structure ◽  
Sedimentary Basins ◽  
Dyke Swarm ◽  
Normal Faults ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Dyke Swarms ◽  
Nw Australia

Abstract. Dyke swarms are common on Earth and other planetary bodies, comprising arrays of dykes that can extend for 10's to 1000's of kilometres. The vast extent of such dyke swarms, and their rapid emplacement, means they can significantly influence a variety of planetary processes, including continental break-up, crustal extension, resource accumulation, and volcanism. Determining the mechanisms driving dyke swarm emplacement is thus critical to a range of Earth Science disciplines. However, unravelling dyke swarm emplacement mechanics relies on constraining their 3D structure, which is extremely difficult given we typically cannot access their subsurface geometry at a sufficiently high enough resolution. Here we use high-quality seismic reflection data to identify and examine the 3D geometry of the newly discovered Exmouth Dyke Swarm, and associated structures (i.e. dyke-induced normal faults and pit craters), in unprecedented detail. The latest Jurassic dyke swarm is located on the Gascoyne Margin offshore NW Australia and contains numerous dykes that are > 170 km long, potentially > 500 km long. The mapped dykes are distributed radially across a 39° arc centred on the Cuvier Margin; we infer this focal area marks the source of the dyke swarm, which was likely a mantle plume. We demonstrate seismic reflection data provides unique opportunities to map and quantify dyke swarms in 3D in sedimentary basins, which can allow us to: (i) recognise dyke swarms across continental margins worldwide and incorporate them into models of basin evolution and fluid flow; (ii) test previous models and hypotheses concerning the 3D structure of dyke swarms; (iii) reveal how dyke-induced normal faults and pit craters relate to dyking; and (iv) unravel how dyking translates into surface deformation.

scholarly journals Structural and microstructural analysis of K–Mg salt layers in the Zechstein 3 of the Veendam Pillow, NE Netherlands: development of a tectonic mélange during salt flow

2017 ◽  
Vol 96 (4) ◽  
pp. 331-351 ◽  
Author(s):  
Alexander F. Raith ◽  
Janos L. Urai ◽  
Jacob Visser
Keyword(s):  
Microstructural Analysis ◽  
Shear Zones ◽  
Horizontal Shear ◽  
X Ray Diffraction ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Tectonic History ◽  
Dynamic Recrystallisation ◽  
Bulk Chemical ◽  
Tectonic Mélange

AbstractIn fully developed evaporite cycles, effective viscosity contrasts of up to five orders of magnitude are possible between different layers, but the structures and mechanics in evaporites with such extreme mechanical stratification are not well understood. The Zechstein 3 unit in the Veendam salt pillow in the Netherlands contains anhydrite, halite, carnallite and bischofite, showing this extreme mechanical stratification. The Veendam Pillow has a complex multiphase salt tectonic history as shown by seismic reflection data: salt withdrawal followed by convergent flow into the salt pillow produced ruptures and folds in the underlying Z3-anhydrite–carbonate stringer and deformed the soft Z3-1b layerWe analysed a unique carnallite- and bischofite-rich drill core from the soft Z3-1b layer by macroscale photography, bulk chemical methods, X-ray diffraction and optical microscopy. Results show high strain in the weaker bischofite- and carnallite-rich layers, with associated dynamic recrystallisation at very low differential stress, completely overprinting the original texture. Stronger layers formed by alternating beds of halite and carnallite show complex recumbent folding on different scales commonly interrupted by sub-horizontal shear zones with brittle deformation, veins and boudinage. We attribute this tectonic fragmentation to be associated with a softening of the complete Z3-1b subunit during its deformation. The result is a tectonic mélange with cm- to 10 m-size blocks with frequent folds and boudinage. We infer that these structures and processes are common in deformed, rheologically strongly stratified evaporites.

scholarly journals Seismic reflection data reveal the 3D structure of the newly discovered Exmouth Dyke Swarm, offshore NW Australia

Solid Earth ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 579-606 ◽  
Author(s):  
Craig Magee ◽  
Christopher Aiden-Lee Jackson
Keyword(s):  
Seismic Reflection ◽  
Surface Deformation ◽  
3D Structure ◽  
Dyke Swarm ◽  
Normal Faults ◽  
Borehole Data ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Dyke Swarms ◽  
Nw Australia

Abstract. Dyke swarms are common on Earth and other planetary bodies, comprising arrays of dykes that can extend laterally for tens to thousands of kilometres. The vast extent of such dyke swarms, and their presumed rapid emplacement, means they can significantly influence a variety of planetary processes, including continental break-up, crustal extension, resource accumulation, and volcanism. Determining the mechanisms driving dyke swarm emplacement is thus critical to a range of Earth Science disciplines. However, unravelling dyke swarm emplacement mechanics relies on constraining their 3D structure, which is difficult given we typically cannot access their subsurface geometry at a sufficiently high enough resolution. Here we use high-quality seismic reflection data to identify and examine the 3D geometry of the newly discovered Exmouth Dyke Swarm, and associated structures (i.e. dyke-induced normal faults and pit craters). Dykes are expressed in our seismic reflection data as ∼335–68 m wide, vertical zones of disruption (VZD), in which stratal reflections are dimmed and/or deflected from sub-horizontal. Borehole data reveal one ∼130 m wide VZD corresponds to an ∼18 m thick, mafic dyke, highlighting that the true geometry of the inferred dykes may not be fully captured by their seismic expression. The Late Jurassic dyke swarm is located on the Gascoyne Margin, offshore NW Australia, and contains numerous dykes that extend laterally for > 170 km, potentially up to > 500 km, with spacings typically < 10 km. Although limitations in data quality and resolution restrict mapping of the dykes at depth, our data show that they likely have heights of at least 3.5 km. The mapped dykes are distributed radially across a ∼39∘ wide arc centred on the Cuvier Margin; we infer that this focal area marks the source of the dyke swarm. We demonstrate that seismic reflection data provide unique opportunities to map and quantify dyke swarms in 3D. Because of this, we can now (i) recognise dyke swarms across continental margins worldwide and incorporate them into models of basin evolution and fluid flow, (ii) test previous models and hypotheses concerning the 3D structure of dyke swarms, (iii) reveal how dyke-induced normal faults and pit craters relate to dyking, and (iv) unravel how dyking translates into surface deformation.

scholarly journals Hydraulic fracturing in thick shale basins: problems in identifying faults in the Bowland and Weald Basins, UK

2016 ◽  
Author(s):  
David K. Smythe
Keyword(s):  
Hydraulic Fracturing ◽  
Seismic Reflection ◽  
Upper Jurassic ◽  
Normal Faults ◽  
Regulatory Regime ◽  
Seismic Line ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Unconventional Resource ◽  
The Uk

Abstract. North American shale basins differ from their European counterparts in that the latter are one to two orders of magnitude smaller in area, but correspondingly thicker, and are cut or bounded by normal faults penetrating from the shale to the surface. There is thus an inherent risk of groundwater resource contamination via these faults during or after unconventional resource appraisal and development. US shale exploration experience cannot simply be transferred to the UK. The Bowland Basin, with 1900 m of Lower Carboniferous shale, is in the vanguard of UK shale gas development. A vertical appraisal well to test the shale by hydraulic fracturing (fracking), the first such in the UK, triggered earthquakes. Re-interpretation of the 3D seismic reflection data, and independently the well casing deformation data, both show that the well was drilled through the earthquake fault, and did not avoid it, as concluded by the exploration operator. Faulting in this thick shale is evidently difficult to recognise. The Weald Basin is a shallower Upper Jurassic unconventional oil play with stratigraphic similarities to the Bakken play of the Williston Basin, USA. Two Weald licensees have drilled, or have applied to drill, horizontal appraisal wells based on inadequate 2D seismic reflection data coverage. I show, using the data from the one horizontal well drilled to date, that one operator failed identify two small but significant through-going normal faults. The other operator portrayed a seismic line as an example of fault-free structure, but faulting had been smeared out by reprocessing. The case histories presented show that: (1) UK shale exploration to date is characterised by a low degree of technical competence, and (2) regulation, which is divided between four separate authorities, is not up to the task. If UK shale is to be exploited safely: (1) more sophisticated seismic imaging methods need to be developed and applied to both basins, to identify faults in shale with throws as small as 4–5 m, and (2) the current lax and inadequate regulatory regime must be overhauled, unified, and tightened up.

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