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.

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.

scholarly journals Geostatistical characterization of internal structure of mass-transport deposits from seismic reflection images and borehole logs

2019 ◽  
Vol 221 (1) ◽  
pp. 318-333
Author(s):  
Jonathan Ford ◽  
Angelo Camerlenghi
Keyword(s):  
Mass Transport ◽  
Internal Structure ◽  
Seismic Reflection ◽  
Slope Failure ◽  
Random Medium ◽  
Seismic Facies ◽  
Strain History ◽  
Borehole Data ◽  
Mass Transport Deposits ◽  
Scale Length

SUMMARY Seismic reflection images of mass-transport deposits often show apparently chaotic, disorded or low-reflectivity internal seismic facies. The lack of laterally coherent reflections can prevent horizon-based interpretation of internal structure. This study instead inverts for geostatistical parameters which characterize the internal heterogeneity of mass-transport deposits from depth-domain seismic reflection images. A Bayesian Markov Chain Monte Carlo inversion is performed to estimate posterior probability distributions for each geostatistical parameter. If the internal heterogeneity approximates an anisotropic von Kármán random medium these parameters can describe the structural fabric of the imaged mass-transport deposit in terms of lateral and vertical dominant scale lengths and the Hurst number (roughness). To improve the discrimination between vertical and lateral dominant scale lengths an estimate of the vertical dominant scale length from a borehole is used as a prior in the inversion. The method is first demonstrated on a synthetic multichannel seismic reflection image. The vertical and lateral dominant scale lengths are estimated with lower uncertainty when data from a synthetic borehole data are included. We then apply the method to a real data example from Nankai Trough, offshore Japan, where a large mass-transport deposit is imaged in a seismic profile and penetrated by a borehole. The results of the inversion show a downslope shortening in lateral scale length, consistent with progressive down-slope disaggregation of the mass-flow during transport. The dominant scale lengths can be used as a proxy for strain history, which can improve understanding of post-failure dynamics and emplacement of subacqueous mass-movements, important for constraining the geohazard potential from future slope failure.

The geological structure and distribution of Paleozoic rocks on the Avalon Platform, offshore Newfoundland

1987 ◽  
Vol 24 (7) ◽  
pp. 1412-1420 ◽  
Author(s):  
P. W. Durling ◽  
J. S. Bell ◽  
G. B. J. Fader
Keyword(s):  
Seismic Reflection ◽  
Single Channel ◽  
Geological Structure ◽  
Structural Mapping ◽  
Grand Banks ◽  
Seismic Reflection Profiles ◽  
Paleozoic Rocks ◽  
Seismic Reflections ◽  
Avalon Peninsula ◽  
Overthrust Belt

Single-channel seismic reflection profiles obtained across the Avalon Platform, offshore Avalon Peninsula, Newfoundland, have been studied for seismic reflections and interpreted in conjunction with lithologic and biostratigraphic data. Formline structural mapping revealed a 4000 m thick Ordovician–Silurian marine shale sequence that is gently folded about north-northwest–south-southeast axes and is unconformably overlain by a synclinal outlier of Devonian(?) redbeds approximately 700 m thick.The Avalon Platform on the Grand Banks may represent a mildly deformed Acadian terrane, which is contiguous with onshore Avalonian sequences, or it may be part of a foreland zone adjacent to an overthrust belt, or both.

Megaclasts within mass-transport deposits: their origin, characteristics and effect on substrates and succeeding flows

2020 ◽  
Vol 500 (1) ◽  
pp. 515-530 ◽  
Author(s):  
Jefferson Nwoko ◽  
Ian Kane ◽  
Mads Huuse
Keyword(s):  
Mass Transport ◽  
Seismic Reflection ◽  
Radial Flow ◽  
Submarine Landslide ◽  
Submarine Landslides ◽  
3D Seismic ◽  
Seafloor Topography ◽  
Basal Surface ◽  
Mass Transport Deposits ◽  
Substrate Influence

AbstractMegaclasts transported within submarine landslides can erode the substrate, influence the flow that transports them and, if they form seafloor topography, can influence subsequent flows and their deposits. We document grooves up to 40 km long formed by megaclasts carried in submarine landslides that scoured tens of metres deep into the contemporaneous substrate of the deep-water Taranaki Basin, New Zealand. A 1925 km2 3D seismic reflection survey records six mass transport deposits (MTDs) interbedded with turbidites. Here, we focus on three MTDs, labelled A (oldest), B and C (youngest). MTD-A features megaclasts that internally have coherent parallel strata, and formed striations 4–15 km long and 2–3 km wide, with protruding megaclasts that are onlapped by younger sediments. The seafloor expression of these megaclasts partially obstructed the submarine landslide that created MTD-B. MTD-B contains megaclasts that incised through the rugose topography of the underlying MTD-A, and formed divergent grooves on the basal surface of MTD-B (8–40 km long and 200–250 m wide), which suggest radial flow expansion where flows exited topographic confinement. MTD-C features grooves 2–6 km long and 100–200 m wide that terminate at megaclasts and which internally are characterized of highly deformed reflectors surrounded by a chaotic matrix. This study directly links megaclasts to the grooves they form, and demonstrates that markedly different styles of scouring and resultant grooves can occur in closely related MTDs.

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.

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