Paleocontinental slopes of East Coast Geosyncline (Canadian Atlantic margin)

1977 ◽  
Vol 14 (11) ◽  
pp. 2553-2564 ◽  
Author(s):  
Lewis H. King ◽  
Ian F. Young
Keyword(s):  
Newfoundland And Labrador ◽  
East Coast ◽  
Shelf Edge ◽  
Mass Wasting ◽  
Scotian Shelf ◽  
Grand Banks ◽  
Shelf Slope ◽  
Seismic Reflection Profiles ◽  
Atlantic Margin ◽  
Upper Slope

A study of processed seismic reflection profiles along the eastern Canadian continental margin indicates the occurrence at depth of paleocontinental slopes of Cenozoic–Mesozoic age, generally in the vicinity of the present continental slope. The paleoslopes are of two general types, constructional and destructional, formed respectively by progradational processes and mass wasting. The inclined beds of the progradational sequence (clinoform beds) represent the constructional slopes and were probably formed at times when deposition was simultaneous on the shelf, slope, and rise. Conditions leading to the establishment of a relatively deep shelf edge would favor constructional slope formation and preservation. A relatively shallow shelf edge, common during times of low sea level, would promote cutback at the shelf edge and upper slope and lead to the formation of destructional slopes. The depth of the shelf edge is mainly established by the balance between rates of sedimentation and subsidence in conjunction with the processes arising from variations in sea level.The sequence of constructional and destructional paleocontinental slopes varies widely along the Canadian Atlantic margin. On the western Scotian Shelf adjacent to the LaHave Platform the paleoslopes are mainly destructional and are in proximity, with only fragmental expression of former constructional slopes remaining. On the eastern Scotian Shelf and Grand Banks destructional paleoslopes are widely spaced in section between thick areas of constructional slope development. Paleoslopes along the northeast Newfoundland and Labrador Shelves are mainly constructional. The differences may be related to age of opening of the Atlantic Basin.The type and distribution of paleocontinental slopes along a margin could influence the migration of hydrocarbons from the eugeocline to the miogeocline.

Late Cenozoic architecture of the St. Pierre Slope

2005 ◽  
Vol 42 (11) ◽  
pp. 1987-2000 ◽  
Author(s):  
David JW Piper ◽  
Adam WA Macdonald ◽  
Stephen Ingram ◽  
Graham L Williams ◽  
Curtis McCall
Keyword(s):  
Mass Transport ◽  
Seismic Reflection ◽  
Failure Surface ◽  
Late Cenozoic ◽  
Grand Banks ◽  
Age Model ◽  
Seismic Reflection Profiles ◽  
Mass Transport Deposits ◽  
Bermuda Rise ◽  
Upper Slope

The late Cenozoic seismic stratigraphy of the continental slope south of western Newfoundland is interpreted using new seismic reflection profiles. New Miocene–Pliocene biostratigraphic (palynology) age determinations on the Hermine E-94 well on the northwestern Grand Banks of Newfoundland are correlated to the study area. The Quaternary section of St. Pierre Slope is disrupted by numerous failure scarps and mass-transport deposits, but correlation from the mid- slope to the continental rise is achieved using major mass-transport deposits as markers. On the upper slope, stacked downslope-thinning wedges of acoustically incoherent sediment are interpreted as till deposits of mid- to late Pleistocene age. Sedi mentation rates in the youngest part of the succession are estimated from a 30 ka radiocarbon date 25 m below the horizon of the youngest till tongue, which is exposed on a 60 m deep failure surface. Extrapolation of sedimentation rates and comparison with dated sections on the J-Anomaly Ridge and Bermuda Rise provides a consistent interpreted age model for the till tongues that corresponds to marine isotope stages 2, 4, 6, 8, 10, and 12.

Ichthyoplankton Associated with a Warm Core Ring off the Scotiars Shelf

1984 ◽  
Vol 41 (2) ◽  
pp. 294-303 ◽  
Author(s):  
J. S. Wroblewski ◽  
Jerry Cheney
Keyword(s):  
Continental Shelf ◽  
Shelf Break ◽  
Shelf Water ◽  
Scotian Shelf ◽  
Larval Drift ◽  
Warm Core ◽  
Warm Core Ring ◽  
Shelf Slope ◽  
Continental Shelf Break ◽  
Upper Slope

A warm core ring and adjacent waters off the Scotian Shelf in June 1982 contained substantial numbers of larval and juvenile white hake, Urophycis tenuis, as far as 140 km seaward of the continental shelf break. The warm core ring, designated 81-G, had entrained shelf water on several occasions before the shipboard observations were made. We suggest that the ring contributed to the offshore advection of these fish, which probably were spawned on the continental shelf or upper slope. Warm core rings can disrupt the usual larval drift pattern of shelf–slope fishes and thereby affect recruitment. Larvae and juveniles of several species of tropical–subtropical fishes found in ring 81-G have been reported previously as rare specimens in ichthyoplankton surveys on the Scotian Shelf. Our observations support the hypothesis that warm core rings can be a mechanism for transport of these expatriated fishes onto the shelf.

scholarly journals Timing and position of Late Wisconsinan ice-margins on the upper slope seaward of Laurentian Channel

2004 ◽  
Vol 55 (2) ◽  
pp. 131-140 ◽  
Author(s):  
David J. W. Piper ◽  
Adam Macdonald
Keyword(s):  
Continental Slope ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Radiocarbon Dates ◽  
Grand Banks ◽  
Last Glacial ◽  
Seismic Reflection Profiles ◽  
The Last Glacial Maximum ◽  
The Last Glacial ◽  
Upper Slope

Abstract At the last glacial maximum, the major ice outlet through Laurentian Channel terminated on the upper continental slope. A 10 km square area of the upper slope has been investigated in detail, using airgun and boomer seismic reflection profiles and piston cores. Sediment failure during the 1929 Grand Banks earthquake resulted in exposure at the seabed of Last Glacial Maximum sediments that are normally buried beneath tens of metres of younger strata. Ice-margin acoustic and lithofacies are interpreted using criteria developed on the continental shelf and chronology is provided by AMS radiocarbon dates on in situ mollusc shells. Seismic data show a morainal ridge at 500 mbsl (mbsl = metres below (present) sea level) corresponding to the Last Glacial Maximum ice grounding line. A change in thermal regime of the ice or a subglacial meltwater outburst, at 16.5 ± 0.15 ka (radiocarbon years, -0.4 ka marine reservoir correction applied), resulted in release of sediment-laden meltwater that eroded gullies on the continental slope. This erosion surface is immediately overlain by a prominent stony diamict that extends to about 700 mbsl and may represent till deposition from a glacial surge. The ice margin then retreated upslope by 16.3 ka, probably to the prominent moraine at 380 mbsl at the lip of the Laurentian Channel. Evidence from mud turbidites on Laurentian Fan suggests that this ice marginal position may have persisted until about 14.2 ka. Ice then retreated rapidly northwards up Laurentian Channel, synchronous with Heinrich Event 1 at about 14 ka. Younger proglacial sediment on the upper continental slope slumped at about 12 ka, probably as a result of loading by a late-ice advance across St. Pierre Bank.

Circulation and water mass characteristics of the southern Great Barrier Reef

1994 ◽  
Vol 45 (1) ◽  
pp. 1 ◽  
Author(s):  
JH Middleton ◽  
P Coutis ◽  
DA Griffin ◽  
A Macks ◽  
A McTaggart ◽  
...  
Keyword(s):  
Great Barrier Reef ◽  
Heat Loss ◽  
Barrier Reef ◽  
Low Oxygen ◽  
Geostrophic Balance ◽  
Shelf Slope ◽  
High Nutrient ◽  
Slope Currents ◽  
North And South ◽  
Upper Slope

Data acquired during a winter (May) cruise of the RV Franklin to the southern Great Barrier Reef indicate that the dynamics of the shelf/slope region are governed by the tides, the poleward-flowing East Australian Current (EAC), and the complex topography. Over the Marion Plateau in water deeper than - 100 m, the EAC appears to drive a slow clockwise circulation. Tides appear to be primarily responsible for shelf/slope currents in the upper layers, with evidence of nutrient uplift from the upper slope to the outer shelf proper in the Capricorn Channel. Elsewhere, the bottom Ekrnan flux of the strongly poleward-flowing EAC enhances the sloping isotherms associated with the longshore geostrophic balance, pumping nutrient-rich waters from depth to the upper continental slope. Generally, shelf waters are cooler than oceanic waters as a consequence of surface heat loss by radiation. A combination of heat loss and evaporation from waters flowing in the shallows of the Great Sandy Strait appears to result in denser 'winter mangrove waters' exporting low-oxygen, high-nutrient waters onto the shelf both north and south of Fraser Island; these subsequently mix with shelf waters and finally flow offshore at - 100 m depth, just above the salinity-maximum layer, causing anomalous nutrient values in the region of Fraser Island.

Upper slope sands: Late Quaternary shallow-water sandy contourities of Campos Basin, SW Atlantic Margin

2002 ◽  
Vol 22 (1) ◽  
pp. 261-270 ◽  
Author(s):  
Adriano R. Viana ◽  
Waldemar De Almeida ◽  
Cleide Wilhelm De Almeida
Keyword(s):  
Shallow Water ◽  
Late Quaternary ◽  
Campos Basin ◽  
Sw Atlantic ◽  
Atlantic Margin ◽  
Upper Slope

Unconformities on the Scotian Shelf

1974 ◽  
Vol 11 (1) ◽  
pp. 89-100 ◽  
Author(s):  
Lewis H. King ◽  
Brian MacLean ◽  
Gordon B. Fader
Keyword(s):  
High Resolution ◽  
Seismic Reflection ◽  
Upper Cretaceous ◽  
Scotian Shelf ◽  
Early Tertiary ◽  
Late Tertiary ◽  
Glacial Processes ◽  
Well Data ◽  
Seismic Reflection Profiles ◽  
Cut And Fill

Four erosional unconformities have been recognized within the Mesozoic-Cenozoic succession on the Scotian Shelf, on the basis of data from high resolution seismic reflection profiles. Older unconformities are known from well data and others may be revealed by detailed biostratigraphic studies.The oldest of the four unconformities discussed in this paper is of Early Cretaceous age and appears to mark, with discordance, the boundary between Jurassic and Cretaceous strata on the western part of the shelf. A second angular unconformity, of Late Cretaceous age, has been recognized on the central part of the shelf where the basal part of the Banquereau Formation (Tertiary and uppermost Cretaceous) oversteps the zero-edge of the Wyandot Formation (Upper Cretaceous) and lies upon truncated beds of the Dawson Canyon Formation (Upper Cretaceous). Cut-and-fill relationships characterize a third unconformity developed during Early Tertiary time. A fourth unconformity was developed in Late Tertiary – Pleistocene time by fluvial processes and later by glacial processes. Although in many areas the latest unconformity appears to be the most conspicuous one on the shelf, its configuration closely follows the geomorphic expression developed during the previous period of erosion. The regional extent of the Cretaceous unconformities is not known, and they might only occur near basin margins and on structural and basement highs.

Low-frequency currents at the northern shelf edge of the Grand Banks

1996 ◽  
Vol 101 (C6) ◽  
pp. 14223-14235 ◽  
Author(s):  
B. M. DeTracey ◽  
C. L. Tang ◽  
P. C. Smith
Keyword(s):  
Low Frequency ◽  
Shelf Edge ◽  
Grand Banks ◽  
Northern Shelf
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