Crustal-scale ramp in a Middle Proterozoic orogen, Northwest Territories, Canada

1992 ◽  
Vol 29 (1) ◽  
pp. 142-157 ◽  
Author(s):  
Elizabeth A. Clark ◽  
Frederick A. Cook

Deep crustal seismic data from the Fort Goodhope area, Northwest Territories, Canada, image crustal structures associated with Middle Proterozoic compressional deformation. These include 10–20 km wide antiforms and thrust faults that lie above a west-dipping crustal-scale ramp with at least 10 km of vertical relief. The deformation is interpreted as being associated with structures observed in the subsurface to the east and may be partly coeval with deformation originally detected in outcrop in the Rackla Range of the Wernecke Mountains. These new deep crustal profiles, coupled with data to the east that delineate structures to 15 km depth, reveal large-scale similarity between this Middle Proterozoic orogen and many Phanerozoic compressional orogens.

2019 ◽  
Vol 500 (1) ◽  
pp. 531-549 ◽  
Author(s):  
Suzanne Bull ◽  
Joseph A. Cartwright

AbstractThis study shows how simple structural restoration of a discrete submarine landslide lobe can be applied to large-scale, multi-phase examples to identify different phases of slide-lobe development and evaluate their mode of emplacement. We present the most detailed analysis performed to date on a zone of intense contractional deformation, historically referred to as the compression zone, from the giant, multi-phase Storegga Slide, offshore Norway. 2D and 3D seismic data and bathymetry data show that the zone of large-scale (>650 m thick) contractional deformation can be genetically linked updip with a zone of intense depletion across a distance of 135 km. Quantification of depletion and accumulation along a representative dip-section reveals that significant depletion in the proximal region is not accommodated in the relatively mild amount (c. 5%) of downdip shortening. Dip-section restoration indicates a later, separate stage of deformation may have involved removal of a significant volume of material as part of the final stages of the Storegga Slide, as opposed to the minor volumes reported in previous studies.


2002 ◽  
Vol 40 (1) ◽  
pp. 83
Author(s):  
Raymond E. Quesnel

This article examines the current core legislation that governs oil and gas activity in Canada's North. While there has been increased industry interest in the Northwest Territories, there has thus far been a lack of actual oil and gas projects against which to measure the efficacy of the current regime in the context of northern development. An historical analysis of the legislative developments indicates that the northern regime formed the basis for the legislative framework now governing east coast megaprojects. The author evaluates the current basis on which rights are granted and recorded, the tenure system, the royalty regime, and the project approval process. He concludes that, while the northern regime is suitable for large scale developments, it may require certain changes to accommodate smaller, more conventional projects likely to be undertaken.


2021 ◽  
pp. SP509-2021-51
Author(s):  
J. Hendry ◽  
P. Burgess ◽  
D. Hunt ◽  
X. Janson ◽  
V. Zampetti

AbstractImproved seismic data quality in the last 10–15 years, innovative use of seismic attribute combinations, extraction of geomorphological data, and new quantitative techniques, have significantly enhanced understanding of ancient carbonate platforms and processes. 3D data have become a fundamental toolkit for mapping carbonate depositional and diagenetic facies and associated flow units and barriers, giving a unique perspective how their relationships changed through time in response to tectonic, oceanographic and climatic forcing. Sophisticated predictions of lithology and porosity are being made from seismic data in reservoirs with good borehole log and core calibration for detailed integration with structural, paleoenvironmental and sequence stratigraphic interpretations. Geologists can now characterise entire carbonate platform systems and their large-scale evolution in time and space, including systems with few outcrop analogues such as the Lower Cretaceous Central Atlantic “Pre-Salt” carbonates. The papers introduced in this review illustrate opportunities, workflows, and potential pitfalls of modern carbonate seismic interpretation. They demonstrate advances in knowledge of carbonate systems achieved when geologists and geophysicists collaborate and innovate to maximise the value of seismic data from acquisition, through processing to interpretation. Future trends and developments, including machine learning and the significance of the energy transition, are briefly discussed.


2004 ◽  
Vol 44 (1) ◽  
pp. 241 ◽  
Author(s):  
A.M. Lockwood ◽  
C. D’Ercole

The basement topography of the Gascoyne Platform and adjoining areas in the Southern Carnarvon Basin was investigated using satellite gravity and seismic data, assisted by a depth to crystalline basement map derived from modelling the isostatic residual gravity anomaly. The resulting enhanced view of the basement topography reveals that the Gascoyne Platform extends further westward than previously indicated, and is bounded by a northerly trending ridge of shallow basement, named the Bernier Ridge.The Bernier Ridge is a product of rift-flank uplift prior to the Valanginian breakup of Gondwana, and lies east of a series of small Mesozoic syn-rift sedimentary basins. Extensive magmatic underplating of the continental margin associated with this event, and a large igneous province is inferred west of the ridge from potential field and seismic data. Significant tectonic events that contributed to the present form of the Bernier Ridge include the creation of the basement material during the Proterozoic assembly of Rodinia, large-scale faulting during the ?Cambrian, uplift and associated glaciation during the early Carboniferous, and rifting of Gondwana during the Late Jurassic. The depositional history and maturity of the Gascoyne Platform and Bernier Ridge show that these terrains have been structurally elevated since the mid-Carboniferous.No wells have been drilled on the Bernier Ridge. The main source rocks within the sedimentary basins west of the Bernier Ridge are probably Jurassic, similar to those in the better-known Abrolhos–Houtman and Exmouth Sub-basins, where they are mostly early mature to mature and within the oil window respectively. Within the Bernier Ridge area, prospective plays for petroleum exploration in the Jurassic succession include truncation at the breakup unconformity sealed by post-breakup shale, and tilted fault blocks sealed by intraformational shale. Plays in the post-breakup succession include stratigraphic traps and minor rollover structures.


Seismic exploration at sea has established that the oceanic crust is completely different from that of the continents. If we accept continental drift, it is therefore necessary to invoke a mechanism for the evolution of new oceanic crust. An attempt is made to locate regions where new oceanic crust may be forming and it is suggested that these regions are related to regions of uprising convection in the mantle. The crustal structures beneath the Red Sea and the Gulf of California are very similar and closer to oceanic than continental. As these are seismically active regions of extension, it seems reasonable to suppose that they represent areas where new oceanic crust is evolving in regions of continental break-up. These rift zones are in continuity with the seismically active oceanic rifts where similar seismic velocities (about 7 km/s) have been found and it is inferred that the oceanic rifts also represent regions where new oceanic crust is evolving. These are generally near the centres of the oceans. The tensional rift zones which are regions of shallow seismicity help to locate regions of rising convection currents in the mantle. It is further suggested that regions of deep and intermediate focus earthquakes locate regions of descending convection currents and maps of earthquake distributions are used to reveal a possible large-scale pattern of mantle convection. It is supposed that new oceanic crust evolves over the rising convection currents. A study is therefore made of the crustal sections for the Red Sea, Gulf of California and mid-oceanic rift regions and these are compared with typical continental and oceanic crusts. A possible mechanism for the evolution of new oceanic crust is given based on the isostatic equilibrium of oceans and continents.


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