scholarly journals Seismic reflection profiles of the Central Scotian Slope, eastern Canada

1987 ◽  
Author(s):  
Keyword(s):  
Seismic Reflection ◽  
Eastern Canada ◽  
Seismic Reflection Profiles

Remnants of a submerged pre-Jurassic (Devonian?) landscape on Orphan Knoll, offshore eastern Canada

1984 ◽  
Vol 21 (1) ◽  
pp. 61-66 ◽  
Author(s):  
L. M. Parson ◽  
D. G. Masson ◽  
R. G. Rothwell ◽  
A. C. Grant
Keyword(s):  
Long Range ◽  
Seismic Reflection ◽  
Alternative Explanation ◽  
Random Distribution ◽  
Eastern Canada ◽  
Sea Floor ◽  
Large Group ◽  
Seismic Reflection Profiles ◽  
Conical Form ◽  
Water Depths

A large group of discrete peaks occurs on the northeastern surface of Orphan Knoll at water depths between 1800 and 2800 m. Long-range side-scan sonographs are used in conjunction with seismic reflection profiles to establish their flattened conical form. They commonly rise to 300 m above the sea floor and occupy basal areas up to 2 km in diameter at that level. Inclusion of the buried lower parts of these mounds may double estimates of both the height and diameter. The sonographs indicate that the mounds have a random distribution within an elongate northwesterly trending belt. Previous suggestions of their possible origin, such as remnants of dykes or ridges of resistant sedimentary strata, are rejected and an alternative explanation of a zone of partially buried Devonian reef knolls is proposed.

Seismic reflection profiles across the "Mine Series" in the Noranda camp of the Abitibi belt, eastern Canada

1995 ◽  
Vol 32 (2) ◽  
pp. 167-176 ◽  
Author(s):  
Pierre Verpaelst ◽  
A. Shirley Péloquin ◽  
Erick Adam ◽  
Arthur E. Barnes ◽  
John N. Ludden ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Reflection ◽  
Mineral Exploration ◽  
Drill Hole ◽  
Seismic Survey ◽  
Volcanic Complex ◽  
Eastern Canada ◽  
Crustal Layer ◽  
High Resolution Data ◽  
Seismic Reflection Profiles

The Abitibi–Grenville Lithoprobe project completed a regional (line 21) and a high-resolution (line 21-1) seismic survey in the Noranda Central Volcanic Complex of the Blake River Group, Abitibi, Quebec. Line 21 provides a regional framework in which the Archean crust is divided into three layers, two of which are discussed here: the uppermost layer, which corresponds to the Blake River Group, is the least reflective, and lies above 4 s (12 km), and the mid-crustal layer, which is composed of a complex pattern of generally east-northeast-dipping reflectors and lies between 4 and 8 s. Within the regional data, the Mine Series of the Central Volcanic Complex is imaged as a semitransparent series of reflectors overlying a highly reflective east-facing structure interpreted as the subvolcanic Flavrian pluton. The high-resolution data (line 21-1) were collected in the vicinity of the Ansil mine. The seismic images in this region can be controlled by surface geology and extensive drill-hole data, and the project was designed to test the applicability of seismic reflection profiling in providing structural and stratigraphic information for use in mineral exploration: shallow-dipping reflectors correlate well with lithological variations or contacts in the volcanic sequence; strong subhorizontal reflectors correspond to diorite and gabbro dykes and sills; several abrupt lateral changes in the reflectivity coincide with known intrusive contacts such as the Lac Dufault pluton.

Probable Late Wisconsinan ice margin on the upper continental slope off St. Pierre Bank, eastern Canada

1988 ◽  
Vol 25 (6) ◽  
pp. 853-865 ◽  
Author(s):  
Denis Bonifay ◽  
David J. W. Piper
Keyword(s):  
Continental Shelf ◽  
Continental Slope ◽  
Seismic Reflection ◽  
Radiocarbon Dating ◽  
Shear Stresses ◽  
Eastern Canada ◽  
Late Wisconsinan ◽  
Acoustic Facies ◽  
Seismic Reflection Profiles ◽  
Basal Shear

Seismic reflection profiles from the continental slope off St. Pierre Bank show a distinctive acoustic facies characterized by incoherent reflections (unit E) overlain by 5–20 m of stratified sediments (units D–A). Cores from unit E include poorly sorted silty diamict, locally overconsolidated and including in places some foraminifera. Stratified sediments also occur in places in this facies.The overlying sediments of units D–A, except for the topmost metre of unit A, have a foraminiferal fauna dominated by Elphidium excavatum forma clavata and Cassidulina reniforme, which has been interpreted elsewhere as indicating ice-margin sedimentation. The sediments contain turbidites and rare ice-rafted detritus, and are bioturbated. Accelerometer mass spectrometer radiocarbon dating of shells from the stratified sediments yielded dates between 3.3 and 11.8 ka. Facies E, the top of which has an extrapolated age of 11.5–12.0 ka, is interpreted as slumped morainal diamict and proglacial sediment resulting from a late Wisconsinan ice surge through Halibut Channel. Low basal shear stresses in this thin ice surge left little record in the mud-accumulating basins of the continental shelf.

scholarly journals Spatial Relationships between Pockmarks and Sub-Seabed Gas in Fjordic Settings: Evidence from Loch Linnhe, West Scotland

Geosciences ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 283
Author(s):  
Allan Audsley ◽  
Tom Bradwell ◽  
John Howe ◽  
John Baxter
Keyword(s):  
Water Column ◽  
Seismic Reflection ◽  
Hot Spot ◽  
Geophysical Data ◽  
Spatial Relationships ◽  
Hydrocarbon Gases ◽  
Offshore Industry ◽  
Seismic Reflection Profiles ◽  
Spot Analysis ◽  
Sedimentary Carbon

Sub-seabed gas is commonly associated with seabed depressions known as pockmarks—the main venting sites for hydrocarbon gases to enter the water column. Sub-seabed gas accumulations are characterized by acoustically turbid or opaque zones in seismic reflection profiles, taking the form of gas blankets, curtains or plumes. How the migration of sub-seabed gas relates to the origin and distribution of pockmarks in nearshore and fjordic settings is not well understood. Using marine geophysical data from Loch Linnhe, a Scottish fjord, we show that shallow sub-seabed gas occurs predominantly within glaciomarine facies either as widespread blankets in basins or as isolated pockets. We use geospatial ‘hot-spot’ analysis conducted in ArcGIS to identify clusters of pockmarks and acoustic (sub-seabed) profile interpretation to identify the depth to gas front across the fjord. By combining these analyses, we find that the gas below most pockmarks in Loch Linnhe is between 1.4 m and 20 m deep. We anticipate that this work will help to understand the fate and mobility of sedimentary carbon in fjordic (marine) settings and advise offshore industry on the potential hazards posed by pockmarked seafloor regions even in nearshore settings.

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