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.

Evidence for Wisconsinan Glaciations in the Verrill Canyon Area, Scotian Slope

1989 ◽  
Vol 31 (1) ◽  
pp. 27-40 ◽  
Author(s):  
David C. Mosher ◽  
David J. W. Piper ◽  
Gustavs V. Vilks ◽  
A. E. Aksu ◽  
Gordon B. Fader
Keyword(s):  
High Resolution ◽  
Continental Slope ◽  
Seismic Reflection ◽  
Outer Shelf ◽  
Scotian Shelf ◽  
Radiocarbon Dates ◽  
Oxygen Isotopic ◽  
Late Wisconsinan ◽  
Seismic Reflection Profiles ◽  
Water Depths

AbstractA composite thickness of about 25 m of sediment has been cored from the Verrill Canyon on the Scotian Slope. It is interpreted that the majority of this sequence was deposited in a glaciomarine environment during oxygen isotopic stage 2 and the top of stage 3. These sediments, as seen in high-resolution seismic reflection profiles, are well stratified, become thicker upslope, are laterally variable in thickness, and pass upslope into possible outer shelf tills. Three wedge-shaped units of incoherent reflections interfinger with the parallel reflections and terminate in water depths greater than 700 m. These wedge-shaped units are interpreted as slumped diamict and outwash deposits. The age of the uppermost wedge-shaped unit is 26,000–21,000 yr based on extrapolation of radiocarbon dates. This unit documents a late Wisconsinan glacier readvance on the outer Scotian Shelf. The underlying wedge-shaped unit, estimated to be 70,000 yrs old, extends further west along the continental slope, and may represent a more extensive early Wisconsinan ice advance. A third wedge-shaped unit, inferred to have formed during isotopic stage 6, is possibly a remnant of the first glaciation in the study area.

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.

scholarly journals Interpretation of shallow seismic profiles over the continental shelf in West Greenland between latitudes 64° and 69°30'N

1980 ◽  
Vol 100 ◽  
pp. 58-61
Author(s):  
E.F.K Zarudzki
Keyword(s):  
Continental Shelf ◽  
Seismic Reflection ◽  
Preliminary Report ◽  
Early Stage ◽  
Sidescan Sonar ◽  
Seismic Profiles ◽  
West Greenland ◽  
Shallow Seismic ◽  
Seismic Reflection Profiles

The work included the study of parts of the data obtained during the survey cruise WESTMAR 78, described in a preliminary report (Brett & Zarudzki, 1979). The data consist of 10 741 km seismic reflection profiles obtained with sparker, sub-bottom, airgun and boomer systems; 8474 km of bathymetric profiles, 3894 km of sidescan sonar profiles and 8545 km of magnetic profiles. The study objectives in the area and its subdivision were established at an early stage.

scholarly journals Seismic-reflection evidence for a deep subglacial trough beneath Jakobshavns Isbræ, West Greenland

1996 ◽  
Vol 42 (141) ◽  
pp. 219-232 ◽  
Author(s):  
Ted S. Clarke ◽  
Keiih Echelmeyer
Keyword(s):  
Seismic Reflection ◽  
Dominant Role ◽  
Ice Thickness ◽  
Shear Stresses ◽  
Outlet Glacier ◽  
West Greenland ◽  
Ice Stream ◽  
Surface Slopes ◽  
Radio Echo Sounding ◽  
Basal Shear

AbstractSeismic-reflection methods were used to determine the ice thickness and basal topography of Jakobshavns Isbræ, a large, fast-moving ice stream/outlet glacier in West Greenland. A method of data analysis was developed which involves the pointwise migration of data from a linear seismic array and a single explosive source; the method yields the depth, horizontal position and slope of the basal reflector. A deep U-shaped subglacial trough was found beneath the entire length of the well-defined ice stream. The trough is incised up to 1500 m into bedrock, and its base lies 1200–1500 m below sea level for at least 70 km inland. Center-line ice thickness along most of the channel is about 2500 m, or about 2.5 times that of the surrounding ice sheet. This prominent bedrock trough was not apparent in existing radio-echo-sounding data. Reflection coefficients indicate that much of the basal interface is probably underlain by compacted, non-deforming sediment. The large ice thickness, coupled with relatively steep surface slopes, leads to high basal shear stresses (200–300 k Pa) along the ice stream. The large shear stresses and lack of a deformable bed imply that internal deformation plays a dominant role in the dynamics of Jakobshavns Isbræ.

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