Late Quaternary sedimentation in St. George's Bay, southwest Newfoundland: acoustic stratigraphy and seabed deposits

1990 ◽  
Vol 27 (7) ◽  
pp. 964-983 ◽  
Author(s):  
J. Shaw ◽  
D. L. Forbes
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Relative Sea Level ◽  
Seismic Reflection Data ◽  
Coarse Sediment ◽  
Reflection Data ◽  
Late Wisconsinan ◽  
Acoustic Facies ◽  
Glaciogenic Sediments ◽  
Glaciomarine Sediments

Shallow seismic reflection data collected in St. George's Bay, southwest Newfoundland, reveal a complex pattern of subsurface topography and acoustic facies. Two basins in the inner bay are underlain by glacially overdeepened valleys that extend to depths in excess of 180 m. Within the thick Quaternary sequence in the inner bay we recognize eight acoustic units. Units 1 (ice contact), 2 (subaqueous outwash), and 3 (draped glaciomarine) record the presence and retreat of a major Late Wisconsinan ice margin. Unit 4 (postglacial mud) has resulted from reworking of glaciogenic sediments in response to changes in relative sea level. Unit 5 (postglacial sand) is a shoreface deposit on the seaward front of the former moraine. Unit 6 (postglacial delta) was formed by fluvial reworking of glaciogenic sediments during the postglacial lowstand of relative sea level. Unit 7 (postglacial barrier–platform) comprises seaward-fining clinoform prisms that have prograded into the basins, and underlie gravel beach-ridge plains at Stephenville and Flat Island. Unit 8 (postglacial spillover) results from entrainment of coarse sediment on the shallow sill and subsequent progradation into the basins of the inner bay.Seabed sediment in the basins is mud where sampled. The submarine platforms associated with the barriers at Stephenville and Flat Island are largely sandy. The sill is covered by a gravel veneer, with irregular patches of sand that coalesce and thicken seawards. Extensive areas of gravel ripples testify to the continued mobility of much of the coarse sediment on the sill.A major ice front in the inner bay was present prior to 13.7 ka BP. The draped glaciomarine sediments, dated at 13.7–11.2 ka BP in nearby Port au Port Bay, were deposited after withdrawal of the ice front to the vicinity of the present coast, during a readvance, and subsequently. During the postglacial lowstand of relative sea level much of the present sill area was emergent.

The postglacial relative sea-level lowstand in Newfoundland

1995 ◽  
Vol 32 (9) ◽  
pp. 1308-1330 ◽  
Author(s):  
John Shaw ◽  
Donald L. Forbes
Keyword(s):  
Sea Level ◽  
Early Period ◽  
Late Glacial ◽  
Relative Sea Level ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Fluvial Incision ◽  
Concentric Pattern ◽  
Glacier Ice ◽  
Late Wisconsinan

Relative sea level in coastal regions of Newfoundland fell from late-glacial maximum levels to postglacial minima in several phases: (i) an early period of high relative sea level, when Late Wisconsinan ice was at the coast and discharging meltwater plumes into the ocean; (ii) a period of rapidly falling relative sea level, during which glaciers retreated inland; and (iii) a period without glacier ice, during which relative sea level continued to fall, but at decreasing rates. Falling relative sea level caused fluvial incision of glacial deposits in some coastal embayments, and culminated with the construction of lowstand marine deltas. These deltas were submerged during the subsequent Holocene transgression. Seismic reflection data from selected deltas show that they comprise wedges of sediment with prograded, seaward-dipping, foreset-style internal reflections. The depth of the relative sea-level lowstand varies spatially, and it was diachronous. It occurred relatively early and deep in peripheral regions (i.e., farther from the centre of the island), but was later and shallower landward, and close to its northern limits. Approximate ages of the lowstand are 9.5 ± 1 ka in the St. George's Bay – Port au Port region, just over 8.6 ka in Hamilton Sound, before 7.0 ka at Swift Current, 8.7 ka at Connoire Bay, just over 8.2 ka in Bay d'Espoir, and ca. 6.5 ka on the Great Northern Peninsula. The relative sea-level minima range down to at least –30 m, and form a concentric pattern around central Newfoundland, similar to the pattern of raised marine limits.

Late glacial stratigraphy and history of the Gulf of St. Lawrence, Canada

1999 ◽  
Vol 36 (8) ◽  
pp. 1327-1345 ◽  
Author(s):  
Heiner Josenhans ◽  
Scott Lehman
Keyword(s):  
Three Dimensional ◽  
Late Glacial ◽  
Seismic Reflection Data ◽  
Glacial Ice ◽  
Reflection Data ◽  
Cape Breton ◽  
Three Dimensional Configuration ◽  
Late Wisconsinan ◽  
Anticosti Island ◽  
Glaciomarine Sediments

The three-dimensional configuration of the Quaternary sediments in the Gulf of St. Lawrence is described based on analysis of 8000 km of high-resolution seismic reflection data complemented by analysis of seven piston cores. Till and or ice-contact deposits, glaciomarine sediments, postglacial basinal muds, and bank-top lagoonal sediments grading to sands and gravels make up the stratigraphic succession. Numerous thick accumulations of ice-contact - morainal deposits and "till tongues" indicate the position of former ice margins. The sequence of breakup of the last glacial ice in the gulf has been interpreted on the basis of these data and associated accelerator mass spectroscopy 14C dates. Grounded ice extended beyond Cabot Strait before 14.3 ka and retreated rapidly to north of Anticosti Island by 13.7 ka. Local residual piedmont lobes of glacial ice within the Cape Breton Channel and Baie des Chaleurs persisted longer, until about 12.2 ka. Ancestral hanging valleys formed the Cape Breton Channel and Baie des Chaleurs and served as conduits for ice lobes that flowed into the deeper Laurentian Channel. As many as four superimposed (Late Wisconsinan) glaciogenic sequences, up to 190 m in composite thickness, occur at the mouths of these (hanging) valleys. The thickest glacial sections were deposited on the southwestward slope of the Laurentian Channel. The surface of the till - ice-contact sediments between 440 and 100 m below present sea level has been extensively modified by iceberg scouring. The deeper limit (440 m) marks the maximum draft of icebergs, which was in large part determined by the thickness of the calving ice front. The disappearance of iceberg scour marks at 100 m is interpreted to have resulted from erosion of the glacial deposits by a Late Wisconsinan transgression whose low stand is suggested by a well-developed terrace on parts of the Magdalen Plateau at a present water depth of 110 m. A piston core that penetrated sediments overlying the uppermost (Late Wisconsinan) till in the Cape Breton Channel is interpreted to represent a deposit of lagoonal or shallow-marine sediments with localized deposits in excess of 65 m thickness. The depositional style of the postglacial deposits suggests sufficient bottom currents to erode sediments on the Magdalen Plateau.

Late Quaternary sequence stratigraphy of the Mackenzie Delta

1996 ◽  
Vol 33 (7) ◽  
pp. 1053-1074 ◽  
Author(s):  
Philip R Hill
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sequence Stratigraphy ◽  
Late Quaternary ◽  
Sediment Supply ◽  
Mackenzie Delta ◽  
Relative Sea Level ◽  
Relative Sea Level Rise ◽  
Healing Phase ◽  
Late Wisconsinan

The Late Wisconsinan and Holocene sequence stratigraphy of the Mackenzie Delta provides insights into the glacial history of the region. The base of the described succession is a hummocky regional reflector interpreted to be a flooding surface formed immediately after retreat of glacial ice from the Mackenzie Trough. Above this flooding surface, two progradational parasequences are present. The first, assigned to the transgressive systems tract, is correlated with the Tutsieta Lake readvance of the ice sheet at approximately 13 000 BP. A flooding surface forming the upper boundary of this parasequence extends inland to at least Inuvik, developing as a response to glacial retreat and early Holocene relative sea level rise. The second parasequence of Holocene deltaic deposits is assigned to the highstand systems tract and is characterized by progressive progradation of the delta into the Mackenzie Trough to a position seaward of the present delta coastline. A distinct reduction in gradient of the most recent delta clinoforms is consistent with other data suggesting regional transgression and is interpreted to represent the development of a healing-phase wedge. The reasons for this recent transgression are not clear, because relative sea level rise has decreased and sediment supply probably increased over the last 2000 years. Transgression may be related to decreased efficiency of channels, increased trapping of sediments by thermokarst lakes, overspill of the delta across the eastern margin of the valley, and (or) progressively greater exposure to wave action as the delta became less sheltered by the confines of the glacial valley.

A Late Wisconsinan Marine Incursion into Cape Cod Bay, Massachusetts

1988 ◽  
Vol 30 (3) ◽  
pp. 237-250 ◽  
Author(s):  
Robert N. Oldale
Keyword(s):  
New England ◽  
Sea Level ◽  
Cape Cod ◽  
Seismic Reflection Data ◽  
Marine Deposits ◽  
Reflection Data ◽  
Cape Cod Bay ◽  
Terminal Zone ◽  
Glacier Ice ◽  
Late Wisconsinan

Reinterpretation of seismic-reflection data from Cape Cod Bay has produced a revised late Wisconsinan history. Acoustically laminated deposits, originally inferred to be glaciolacustrine, are shown to be glaciomarine by tracing them to glaciomarine mud in Stellwagen Basin, north of Cape Cod Bay. A late Wisconsinan marine deposit of nonglacial origin overlies the glaciomarine deposits in Cape Cod Bay. Both deposits indicate that the crust was isostatically depressed below the late Wisconsinan eustatic sea level and that deglaciation and marine submergence occurred simultaneously. Valleys cut into the marine deposits, both glacial and nonglacial, indicate that a low sea-level stand, the result of isostatic rebound, occurred shortly after the marine incursion. A transgressive uncomformity and marine deposits, both mostly of Holocene age, overlie the late Wisconsinan deposits. The marine incursion, regression, and Holocene transgression represent the northward passage of an isostatically induced peripheral bulge following deglaciation. In turn, the bulge, a response to crustal loading and unloading, indicates thick glacier ice in the terminal zone and lends support to arguments for a maximum Laurentide ice model. Evidence for a late Wisconsinan marine incursion, regression, and the passage of a peripheral bulge should be sought in the other bays and sounds of the New England terminal zone.

scholarly journals Late Quaternary Deglaciation, Glaciomarine Sedimentation and Glacioisostatic Recovery in the Rivière Nastapoka Area, Eastern Hudson Bay, Northern Québec

2005 ◽  
Vol 57 (1) ◽  
pp. 65-83 ◽  
Author(s):  
Patrick Lajeunesse ◽  
Michel Allard
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Phase 1 ◽  
Second Phase ◽  
Hudson Bay ◽  
Silty Clay ◽  
Paleoenvironmental Reconstruction ◽  
Relative Sea Level ◽  
Radiocarbon Dates ◽  
Fluvial Terraces

Abstract This study presents a paleoenvironmental reconstruction of deglaciation dynamics and chronology, glaciomarine and postglacial sedimentation, as well as glacioisostatic recovery in the Rivière Nastapoka area, eastern Hudson Bay. Results indicate that the retreat of Québec-Labrador ice was mainly controlled by topography and was marked by four phases. Radiocarbon dates indicate that deglaciation began about 8.3 ka cal. BP and was characterized by a stillstand of the ice margin in the Nastapoka Hills that lead to the deposition of a drift belt in a high relative sea-level (Phase 1). After this stabilisation, the ice margin retreated rapidly eastward in a region of low relief and deposited a drape of silty clay in a falling relative sea-level (Phase 2). A second phase of stabilization of the ice margin lasted until at least 7.2 ka cal.BP on the higher shield peneplaine east of the limit of the Tyrrell Sea (Phase 3). This lead to the deposition of a belt of glaciofluvial deltas in a lower relative sea-level. Following this stillstand, the eastward retreat and subsequent ablation of the ice in central Québec-Labrador generated meltwater that transported large volumes of glacial sediments by fluvial processes and downcutting of fluvial terraces in previously deposited glaciofluvial and marine sediments (Phase 4). Glacioisostatic rebound reached 0.07 m/yr during the early phase of deglaciation and decreased to 0.04 m/yr between 6 and 5 ka cal. BP and 0.016 m/yr in the last 1000 years.

Late Quaternary relative sea-level changes and vertical movements at Lipari (Aeolian Islands)

2002 ◽  
Vol 17 (5-6) ◽  
pp. 459-467 ◽  
Author(s):  
N. Calanchi ◽  
F. Lucchi ◽  
P. A. Pirazzoli ◽  
C. Romagnoli ◽  
C. A. Tranne ◽  
...  
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Vertical Movements ◽  
Aeolian Islands

A reconnaissance survey of late Quaternary sea levels, Bella Bella/Bella Coola region, central British Columbia coast

1978 ◽  
Vol 15 (3) ◽  
pp. 341-350 ◽  
Author(s):  
J. T. Andrews ◽  
R. M. Retherford
Keyword(s):  
British Columbia ◽  
Sea Level ◽  
Late Quaternary ◽  
Middle Part ◽  
Relative Sea Level ◽  
Marine Transgression ◽  
Sea Levels ◽  
Reconnaissance Survey ◽  
Rate Of Emergence ◽  
Bella Coola

A preliminary relative sea level curve that covers the last 10 200 years is derived for the area of the islands and outer mainland centered on Bella Bella and Namu, the central coast of British Columbia. The curve shows postglacial emergence of 17 m over this period. The rate of emergence was ~0.6 m/100 year about 9000 BP, and present sea level was attained between 7000 and 8000 BP. Relative sea level continued to fall until the last few hundred to one thousand years BP when a marine transgression led to a rise of sea level and resultant erosion of many coastal Indian middens. Marine limits on the outer islands may reach 120 m asl, whereas in the middle part of the fiord country observed delta surfaces are lower (54–75 m asl). Elevations of raised deltas then attain ~150 m at fiord heads. A readvance of the ice front ≤ 12 210 ± 330 BP (GSC-1351) is suggested by the stratigraphy of one section.

Dynamics and evolution of continental margin clinoform systems

2020 ◽  
Author(s):  
Gerben de Jager ◽  
Dicky Harishidayat ◽  
Benjamin Emmel ◽  
Ståle Emil Johansen
Keyword(s):  
Sea Level ◽  
Continental Margin ◽  
Water Depth ◽  
Large Scale ◽  
Barents Sea ◽  
Source Rocks ◽  
Sea Level Changes ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Geological Processes

<p>Clinoforms are aquatic sedimentary features commonly associated with strata prograding from a shallower water depth into a deeper water depth. They are very sensitive to changes in water depth, rapidly moving along the shelf in response to sea level changes.  By reconstructing the initial clinoform geometry of buried clinoforms, an estimate of the paleo water depth (PWD) can be made. When this is done for several subsequent clinoform sets the amounts and rates of bathymetric changes can be calculated.</p><p>Here we present a novel approach to estimate clinoform parameters and depositional depths for continental margin clinoforms using seismic reflections, wellbore and biostratigraphy data. Seismic interpretation of three relatively east-west regional full-stack seismic reflection data from the continental margin of the western Barents Sea revealed twelve Late Cenozoic horizons. The clinoform shapes have been restored by removing the effects of compaction and flexural isostasy (backstripping). This includes the effects of glacial/interglacial scenarios on horizons with strong glaciomarine seismic indications.</p><p>Based on the reconstructed clinoform geometries we use empirical relationships from literature between clinoform geometry and depositional depth to estimate PWD values. In these analyses it is possible to estimate the PWD of the upper rollover point and the toe point by measuring the bottomset height, foreset height and topset height. A sensitivity analysis study has also been done on several different scenarios, varying elastic thickness, decompaction and net to gross ratio. Comparison with biostratigraphic water depth estimates indicate that PWD estimates revealed from clinoform parameters give reliable results.</p><p>Any mismatch between the backstripped PWD values and the PWD values derived from the clinoform geometry can then be attributed to geological processes not included in the backstripping process. Among others, these could be explained by rifting, thermal effects in the lithosphere, faulting or eustatic sea level changes. This allows the quantification of the magnitude of these large-scale crustal processes through time.</p><p>We will demonstrate that this method can further constrain the PWD on the continental margin clinoform system and thus can help to improve the understanding of the interplay between sedimentary processes and large-scale crustal processes. Furthermore, the PWD estimates will be a reliable input for further analysis of source-to-sink and stratigraphic forward modeling studies as well as reservoir and source rocks prediction on the petroleum development and exploration.</p><p> </p>

A comparison of observed and theoretical postglacial relative sea level in Atlantic Canada

1981 ◽  
Vol 18 (7) ◽  
pp. 1146-1163 ◽  
Author(s):  
Garry Quinlan ◽  
Christopher Beaumont
Keyword(s):  
Sea Level ◽  
Field Data ◽  
Sea Level Change ◽  
Atlantic Canada ◽  
Relative Sea Level ◽  
Level Curves ◽  
Level Change ◽  
The Common ◽  
Late Wisconsinan ◽  
Outermost Zone

Two extreme models of late Wisconsinan ice cover in Atlantic Canada and the northeastern U.S.A. are shown to produce postglacial relative sea level curves that bracket existing field observations at six sites throughout the region. This suggests that the true late Wisconsinan ice distribution is probably intermediate to the two contrasting reconstructions proposed. Both ice models predict the existence of four relative sea level zones: an innermost zone closest to the centre of glaciation in which relative sea level falls continuously throughout postglacial time; an outermost zone in which it rises continuously; and two transitional zones in which it first falls and then rises in varying proportions according to the distance from the ice margin. The distinctive forms of the relative sea level curves are probably representative of each of the zones and are unlikely to be significantly perturbed even by large local ice readvances. They, therefore, establish patterns with which future field data are expected to conform. The form that the geological record of relative sea level change is likely to take within each zone is discussed and promising settings for the collection of new data are proposed. The common practice of separating relative sea level into an isostatic and a eustatic component is analysed and shown to be incorrect as usually applied. The practice is also shown to be unnecessary because the models discussed in this paper predict changes in relative sea level that can be compared directly with the observations.

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