Integrated geophysical interpretation of crustal structures in the northern Abitibi belt: constraints from seismic amplitude analysis

1996 ◽  
Vol 33 (9) ◽  
pp. 1343-1362 ◽  
Author(s):  
Guy Sénéchal ◽  
Marianne Mareschal ◽  
Andrew J. Calvert ◽  
Gilles Grandjean ◽  
Claude Hubert ◽  
...  
Keyword(s):  
Lower Crust ◽  
Seismic Reflection ◽  
Seismic Energy ◽  
Amplitude Analysis ◽  
Depth Of Penetration ◽  
Tectonic Zone ◽  
Maximum Information ◽  
Seismic Reflection Data ◽  
The North ◽  
Plutonic Belt

We present a processing sequence that attempts to balance geometrical and amplitude analyses in order to recover the maximum information from deep seismic reflection data. The approach, which is guided by the interpretation of other deep geophysical data sets (magnetotellurics, refraction), is applied to Lithoprobe seismic reflection line 28 across the central and northern Abitibi belt. We show, in particular, how amplitude analyses help to quantify the depth of penetration of seismic energy as well as the crustal reflectivity. Apparent lateral variations of deep structures (e.g., the Moho) can be directly related to the high levels of noise that limit the signal penetration depth. We propose a geological model that satisfies all deep geophysical constraints. In this model, the mid crust south of Casa-Berardi tectonic zone consists of imbricated volcanic–plutonic and sedimentary lithologies, which are probably comparable to the mid-crustal section of the Kapuskasing structural zone, and in this paper are referred to as "the Abitibi plate." The lithologies are characterized by high reflectivity, while north of Casa-Berardi tectonic zone the mid crust is dominantly Opatica plutonic lithologies, of lower reflectivity. In this scenario, supracrustal rocks of the Abitibi belt overlie the Opatica plutonic belt, whereas the Abitibi plate extends beneath the Opatica plutonic belt. The boundary between the Opatica plutonic belt and the Abitibi plate is a northward-dipping décollement extending from mid crust in the south to lower crust in the north. The Casa-Berardi tectonic zone appears to be a crustal boundary affecting upper and middle crust down to 20 km, between northern polycyclic terranes and southern monocyclic ones. The uniformity of the lower crust suggests that its formation was decoupled from that of the intermediate to upper crust.

Seismic images of the Grenville Orogen in Ontario

1994 ◽  
Vol 31 (2) ◽  
pp. 293-307 ◽  
Author(s):  
D. J. White ◽  
R. M. Easton ◽  
N. G. Culshaw ◽  
B. Milkereit ◽  
D. A. Forsyth ◽  
...  
Keyword(s):  
Shear Zone ◽  
Seismic Data ◽  
Lower Crust ◽  
Wide Band ◽  
The South ◽  
Tectonic Zone ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Crustal Shortening ◽  
The North

In 1990, Lithoprobe acquired 240 km of seismic-reflection data across parts of the Central Gneiss Belt (CGB) and the Central Metasedimentary Belt (CMB) within the western Grenville Province of southern Ontario. Interpretation of these data in conjunction with geological constraints provided by bedrock mapping supports a model of northwest-directed thrusting and crustal shortening for the Grenville Orogen. Within the CGB, the Parry Sound shear zone is imaged as a 3 km wide zone of reflections dipping southeastward at 20–25° and soling at depths < 7 km in the north and < 3 km in the south beneath Parry Sound domain. Parry Sound domain and the immediately adjacent domains are underlain by a gently southeast-dipping reflective zone at 4.5–12.0 km depth interpreted as a detachment surface, likely associated with the central Britt shear zone. This zone may have accommodated northwesterly transport of Parry Sound, southern Britt, and northwestern Rosseau domains over Britt domain during Grenvillian thrusting.Within the CMB, the seismic data indicate that crustal shortening and imbrication have not been confined to domain and terrane boundaries, as presently defined. A 6 km wide band of reflections dips south at ~20° from the surface within Bancroft terrane, soling into a mid-crustal décollement beneath Elzevir terrane. Beneath and to the north of this planar reflective zone is a complex pattern of strong, south-dipping (10–40°) reflections that extends from the near surface to the lower crust above a less reflective wedge-shaped zone. The zone of complex reflectivity projects updip to the CMB boundary zone and into the CGB; together with the linear band of reflections affiliated with Bancroft terrane, they form the tectonized boundary between the CGB and the CMB. To the south of the linear reflective zone, prominent reflective packages are restricted to the middle and upper crust. The generally nonreflective uppermost crust beneath Elzevir terrane is underlain by a series of gently southeast-dipping, antiformal reflections that appear to sole into the mid-crustal décollement beneath Mazinaw terrane. These observations suggest that the collision between the CMB and the CGB resulted in a sequence of relatively thin (15–20 km thick) allochthonous terranes within the CMB being transported along a regional décollement and thrust northwestward over footwall rocks of the CGB along a penetratively deformed tectonic zone, while a lower crustal wedge may have delaminated the CMB lower crust. Crustal thickness where defined by the seismic data is 42.0–43.5 km in both the CGB and the CMB.

Deep seismic reflection data from the Bay of Fundy and Gulf of Maine: tectonic implications for the northern Appalachians

1991 ◽  
Vol 28 (7) ◽  
pp. 1096-1111 ◽  
Author(s):  
C. E. Keen ◽  
W. A. Kay ◽  
D. Keppie ◽  
F. Marillier ◽  
G. Pe-Piper ◽  
...  
Keyword(s):  
Nova Scotia ◽  
Seismic Reflection ◽  
Gulf Of Maine ◽  
Deep Penetration ◽  
United States Geological Survey ◽  
Bay Of Fundy ◽  
Seismic Reflection Data ◽  
The North ◽  
Geological Features ◽  
Lower Crustal

Three deep-penetration seismic reflection profiles were collected off southwest Nova Scotia to determine the crustal structure and geometry beneath the Avalon and Meguma zones of the Appalachian Orogen in Canada. Onshore geological features have been traced seawards using new gravity and magnetic anomaly maps. The seismic data can also be correlated with the previous United States Geological Survey profile in the central Gulf of Maine.Two seismically distinct lower crustal blocks are identified: the Avalon and Sable lower crustal blocks, separated by a major north-dipping reflection zone that cuts the entire crust. The recognition of the Sable block adds a fourth block to the three already identified in the Canadian Appalachians. The Sable block is overlain by the Meguma Zone. The Avalon Zone overlies at least the northern part of the Avalon lower crustal block. Although offshore extension of geological features is not unequivocal, it appears that a north-dipping reflection zone southwest of Nova Scotia marks the site of Devonian thrusting of Avalon Zone over Meguma Zone. In the Bay of Fundy to the north, two south-dipping reflection zones are interpreted as major thrusts, possibly placing Avalon lower crust over a unit with different tectonic affinities. The Fundy Fault is a Carboniferous thrust within the Avalon block along the coast of New Brunswick; this was reactivated during Mesozoic extension as a transtensional fault. Extensional displacement farther southwest was probably accommodated along east-west-trending faults and small rift basins associated with them.

scholarly journals Geophysical imaging of porosity variations in the Danish North Sea chalk

2008 ◽  
Vol 15 ◽  
pp. 17-20 ◽  
Author(s):  
Tanni Abramovitz
Keyword(s):  
North Sea ◽  
Seismic Reflection ◽  
Seismic Inversion ◽  
Rock Properties ◽  
Well Log ◽  
Reservoir Properties ◽  
Seismic Reflection Data ◽  
Log Data ◽  
The North ◽  
The North Sea

More than 80% of the present-day oil and gas production in the Danish part of the North Sea is extracted from fields with chalk reservoirs of late Cretaceous (Maastrichtian) and early Paleocene (Danian) ages (Fig. 1). Seismic reflection and in- version data play a fundamental role in mapping and characterisation of intra-chalk structures and reservoir properties of the Chalk Group in the North Sea. The aim of seismic inversion is to transform seismic reflection data into quantitative rock properties such as acoustic impedance (AI) that provides information on reservoir properties enabling identification of porosity anomalies that may constitute potential reservoir compartments. Petrophysical analyses of well log data have shown a relationship between AI and porosity. Hence, AI variations can be transformed into porosity variations and used to support detailed interpretations of porous chalk units of possible reservoir quality. This paper presents an example of how the chalk team at the Geological Survey of Denmark and Greenland (GEUS) integrates geological, geophysical and petrophysical information, such as core data, well log data, seismic 3-D reflection and AI data, when assessing the hydrocarbon prospectivity of chalk fields.

Rift processes in the Westralian Superbasin, North West Shelf, Australia: insights from 2D deep reflection seismic interpretation and potential fields modelling

2015 ◽  
Vol 55 (2) ◽  
pp. 400 ◽  
Author(s):  
Catherine Belgarde ◽  
Gianreto Manatschal ◽  
Nick Kusznir ◽  
Sonia Scarselli ◽  
Michal Ruder
Keyword(s):  
Seismic Reflection ◽  
Potential Fields ◽  
Moho Depth ◽  
Late Permian ◽  
Forward Modelling ◽  
Seismic Reflection Data ◽  
North West ◽  
Reflection Seismic ◽  
The North ◽  
Reflection Data

Acquisition of long-offset (8–10 km), long-record length (12–18 sec), 2D reflection seismic and ship-borne potential fields data (WestraliaSpan by Ion/GXT and New Dawn by PGS) on the North West Shelf of Australia provide the opportunity to study rift processes in the context of modern models for rifted margins (Manatschal, 2004). Basement and Moho surfaces were interpreted on seismic reflection data. Refraction models from Geoscience Australia constrain Moho depth and initial densities for gravity modelling through standard velocity-density transformation. 2D joint inversion of seismic reflection and gravity data for Moho depth and basement density constrain depth to basement on seismic. 2D gravity and magnetic intensity forward modelling of key seismic lines constrain basement thickness, type and density. Late Permian and Jurassic-Early Cretaceous rift zones were mapped on seismic reflection data and constrained further by inversion and forward modelling of potential fields data. The Westralian Superbasin formed as a marginal basin in Eastern Gondwana during the Late Permian rifting of the Sibumasu terrane. Crustal necking was localised along mechanically-weak Proterozoic suture belts or Early Paleozoic sedimentary basins (such as Paterson and Canning). Mechanically-strong cratons (such as Pilbara and Kimberley) remained intact, resulting in necking and hyper-extension at their edges. Late Permian hyper-extended areas (such as Exmouth Plateau) behaved as mechanically-strong blocks during the Jurassic to Early Cretaceous continental break-up. Late Permian necking zones were reactivated as failed-rift basins and localised the deposition of the Jurassic oil-prone source rocks that have generated much of the oil discovered on the North West Shelf.

A NORTH WEST SHELF TRIASSIC REEF PLAY: RESULTS FROM ODP LEG 122

1989 ◽  
Vol 29 (1) ◽  
pp. 328 ◽  
Author(s):  
P.E. Williamson ◽  
N.F. Exon ◽  
B. ul Haq ◽  
U. von Rad
Keyword(s):  
Seismic Reflection ◽  
Upper Triassic ◽  
Seismic Facies ◽  
Late Triassic ◽  
Seismic Reflection Data ◽  
Reef Complex ◽  
North West ◽  
Exmouth Plateau ◽  
The North ◽  
Reflection Data

Site 764 of the Ocean Drilling Program (ODP), drilled during Leg 122 in the Exmouth Plateau region, cored 200 m of Upper Triassic (Rhaetian) reef complex. This site, on the northern Wombat Plateau (northernmost Exmouth Plateau) represents the first discovery of Triassic reefal material near the Australian North West Shelf. Seismic reflection data through Site 764 show that the reef itself corresponds predominantly to a seismically poorly reflective zone. A number of regional unconformities appear to correspond, however, to traceable seismic horizons which pass with reduced amplitude through the reef, indicating stages of reef growth separated by erosion or non- deposition. Seismic facies around the edges of the reef are consistent with the deposition of wedges of prograding reef- derived detritus.Application of the seismic criteria for reef recognition established at ODP Site 764, to other seismic reflection data on the Wombat Plateau, demonstrates that a major Upper Triassic reef complex fringes the margins of the Wombat Plateau. The Wombat Plateau lies at the western end of the North West Shelf, which was part of the southern margin of a warm Tethys Ocean in the Late Triassic, at a palaeolatitude of 25- 30°S. Upper Triassic reefs are known from southeast Indonesia and Papua New Guinea, and now the Wombat Plateau, and may be common elsewhere along the outer margin of the North West Shelf. Upper Triassic reef complexes, with their associated reservoir, source and seal facies, could represent an exciting new petroleum exploration play for the entire North West Shelf. Facies analysis suggests that they are likely only on the outer shelf and slope. Shallow Triassic reef complexes are clearly identifiable using high resolution seismic reflection data. Seismic reflection data of lower resolution may well reveal the associated detrital carbonate wedges, which are more laterally extensive than the reefal core, deeper in the section.

Seismic History of Minnesota and It’s Geological Significance: An Update

1989 ◽  
Vol 60 (2) ◽  
pp. 79-86 ◽  
Author(s):  
Val W. Chandler ◽  
G. B. Morey
Keyword(s):  
Seismic Reflection ◽  
Focal Plane ◽  
Large Earthquake ◽  
Aeromagnetic Data ◽  
Tectonic Zone ◽  
The North ◽  
History Of ◽  
Plane Solution ◽  
Stress Buildup

Abstract High-resolution aeromagnetic data have recently been acquired for most of Minnesota under the sponsorship of the Minnesota Future Resources Commission, which also provided funds for test drilling of selected anomalies. The new data show that northwest-trending dikes and fractures are much more common in the Archean terranes than previously believed, and several epicenters are near such faults. The northeast-trending Great Lakes tectonic zone (GLTZ) was thought to be the chief source of seismicity in the state, because several epicenters were aligned with it. However, more recent seismic reflection profiling has demonstrated that the GLTZ has a moderate dip to the north. This dip is not compatible with the previously favored focal plane solution for a relatively large earthquake, which apparently confirmed the seismogenic role of the GLTZ. The alternative focal plane solution for this earthquake, however, is compatible with some northwest-trending structures in the region. We propose that the apparent alignment of epicenters with the GLTZ is related to stress buildup at places where it is intersected by northwest-trending faults, with subsequent movement occurring upon release. A similar model may explain seismicity along the northeast-trending Colorado lineament to the southwest.

Reflection seismic surveys to site the Drilling the Ivrea Verbano zonE (DIVE) proposed drill-holes, Val Sesia and Val d’Ossola, Italy.

2020 ◽  
Author(s):  
Andrew Greenwood ◽  
Ludovic Baron ◽  
Yu Liu ◽  
György Hetényi ◽  
Klaus Holliger ◽  
...  
Keyword(s):  
Continental Crust ◽  
Transition Zone ◽  
Lower Crust ◽  
Seismic Reflection ◽  
Spatial Scales ◽  
Seismic Reflection Data ◽  
Seismic Surveys ◽  
Crustal Rocks ◽  
Drill Holes ◽  
Lower Crustal

&lt;p&gt;The Ivrea-Verbano Zone in the Italian Alps represents one of the most complete and best-studied cross-sections of the continental crust. Here, geological and geophysical observations indicate the presence of the Moho transition zone at shallow depth, possibly as shallow as 3 km in the location of Balmuccia in Val Sesia. Correspondingly, the Ivrea-Verbano Zone is a primary target for assembling data on the deep continental crust as well as for testing several hypotheses regarding its formation and evolution.&lt;/p&gt;&lt;p&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; Within the context of a project submitted to the International Continental Scientific Drilling Program (ICDP), the Drilling the Ivrea-Verbano zonE (DIVE) team proposes to establish three drill holes across pertinent structures within the Ivrea-Verbano Zone. Two of the planned drill holes, each with a length of ~1000 m, are within Val d&amp;#8217;Ossola and target the Pre-Permian lower and upper section of the lower crust. The third proposed drill hole, with a length of ~4000 m, is targeting the lower most crust of the Permian magmatic system of the Ivrea-Verbano Zone in the Val Sesia, close to the Insubric Line. Combined, the three drill holes will compose a complete section of the lower crust and the Moho transition zone, and will reveal the associated structural and composition characteristics at different scales.&lt;/p&gt;&lt;p&gt;To bridge across the range of spatial scales and to support the drilling proposal, we have carried out active seismic surveys using an EnviroVibe source in the Val d&amp;#8217;Ossola. These surveys combined 2D transects (in-line) with the simultaneous collection of short cross-lines, and spatially varied source points, to collect sparse 3D data with a preferential CMP coverage across strike. This survey geometry was largely controlled by environmental considerations and access for the vibrator. Accordingly, 2D profiles, both in-line and cross-line, have been processed using crooked-line geometries, which include CMPs from the 3D infill.&lt;/p&gt;&lt;p&gt;The very high acoustic impedance contrast of the Quaternary valley infill sediments with respect to the predominant metapelitic and gabbroic lower crustal rocks, as well as the highly attenuative nature of the sediments, were both beneficial and problematic. The former enables mapping of the valley structure, while the latter largely prevents the detection of low-amplitude reflections from within the underlying lower crustal rocks.&lt;/p&gt;&lt;p&gt;Here, we present the latest results of these seismic reflection surveys and discuss the observations with respect to the prevailing structure and the planning of the drilling operations. Beyond the specific objectives pursued in this study, our results have important implications with regard to the acquisition and processing of high-resolution seismic reflection data in crystalline terranes and their capacity for resolving complex, steeply dipping structures.&lt;/p&gt;

Reprocessing of deep seismic reflection data from the North German Basin with the Common Reflection Surface stack

2009 ◽  
Vol 472 (1-4) ◽  
pp. 273-283 ◽  
Author(s):  
Mi-Kyung Yoon ◽  
Mikhail Baykulov ◽  
Stefan Dümmong ◽  
Heinz-Jürgen Brink ◽  
Dirk Gajewski
Keyword(s):  
Seismic Reflection ◽  
North German Basin ◽  
Seismic Reflection Data ◽  
Deep Seismic Reflection ◽  
The North ◽  
Reflection Data ◽  
Common Reflection Surface ◽  
The Common ◽  
German Basin
Sign in / Sign up

Export Citation Format

Share Document