A 10,000 yr B.P. Extensive Ice Shelf over Viscount Melville Sound, Arctic Canada

1984 ◽  
Vol 22 (1) ◽  
pp. 18-30 ◽  
Author(s):  
Douglas A. Hodgson ◽  
Jean-Serge Vincent
Keyword(s):  
Sea Level ◽  
North Coast ◽  
Major Advance ◽  
Ice Shelf ◽  
The North ◽  
Minimum Age ◽  
Western Arctic ◽  
Late Wisconsinan ◽  
Victoria Island ◽  
Glacial Landforms

Late Wisconsinan age glacial landforms and deposits indicate that an ice shelf of at least 60,000 km2 flowed northwestward into Viscount Melville Sound, probably from the M'Clintock Dome of the Laurentide Ice Sheet. The ice shelf overlapped coastal areas and laid Winter Harbour Till up to 125 m above present sea level on the southern coast of Melville Island, to 135 m on Byam Martin Island, to possibly 90 m on the northeast tip of Banks Island, and to 150 m on the north coast of Victoria Island. The contemporary sea level was 50 to 100 m higher than present (it now rises eastward). A maximum age of 10,340 ± 150 yr B.P. for the till, and thus the ice-shelf advance, is provided by shells in marine sediments which underlie it, whereas a minimum age of 9880 ± 150 yr B.P. is provided by overlying shells that postdate the ice advance. The major advance of shelf ice into Viscount Melville Sound may be the result of the rapid disintegration of the M'Clintock Dome while the climate ameliorated in the western Arctic.

scholarly journals Changing Sea-Level along the North Coast of Kuwait Bay

1983 ◽  
Vol 73 (4) ◽  
pp. 453
Author(s):  
Alexander Melamid ◽  
Taiba A. Al-Asfour
Keyword(s):  
Sea Level ◽  
North Coast ◽  
Kuwait Bay ◽  
The North

scholarly journals Glacial and Postglacial History of the White Cloud Peaks-Boulder Mountains, Idaho, U.S.A.

2007 ◽  
Vol 40 (3) ◽  
pp. 229-238 ◽  
Author(s):  
James F. P. Cotter ◽  
James M. Bloomfield ◽  
Edward B. Evenson
Keyword(s):  
Sediment Accumulation ◽  
Climatic Conditions ◽  
The North ◽  
Stratigraphic Model ◽  
Glaciofluvial Deposits ◽  
Dry Conditions ◽  
Minimum Age ◽  
Late Wisconsinan ◽  
Mount St Helens ◽  
Peak Set

ABSTRACT Glacial and glaciofluvial deposits are mapped and differentiated to develop new local, relative-age (RD) stratigraphies for the North Fork of the Big Lost River, Slate Creek and Pole Creek drainages in the White Cloud Peaks and Boulder Mountains, Idaho. This stratigraphic model expands the areal extent of the "Idaho glacial model". Volcanic ash samples collected from the study area are petrographically characterized and correlated, on the basis of mineralogy and glass geochemistry, to reference samples of identified Cascade Range tephras. Four distinct tephras are recognized including; Mount St. Helens-Set S (13,600-13,300 yr BP), Glacier Peak-Set B (11,250 yr BP), Mount Mazama (6600 yr BP) and Mount St. Helens-Set Ye (4350 yr BP). A core of lake sediments containing two tephra units was obtained from a site called "Pole Creek kettle". Pollen and sediment analyses indicate three intervals of late Pleistocene and Holocene climatic change. Cool and wet climatic conditions prevailed in the region shortly before and immediately following the deposition of the Glacier Peak-Set B ash (11,250 yr BP). Climatic warming occurred from approximately 10,500 to 6600 yr BP after which warm, dry conditions prevailed. Sediment accumulation in the kettle ceased by 4350 yr BP. The presence of Glacier Peak-Set B tephra in the base of the Pole Creek kettle core provides a minimum age of 11,250 yr BP for the retreat of valley glaciers from their Late Wisconsinan maximum position. A radiocarbon date of 8450 + 85 yr BP (SI-5181), and the presence of Mount Mazama ash (6600 yr BP) up-core support the Glacier Peak-Set B identification.

scholarly journals III.—On a Soda Felspar Rock at Dinas Head, North Coast of Cornwall

1895 ◽  
Vol 2 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Howard Fox
Keyword(s):  
Sea Level ◽  
North Coast ◽  
The North

Dinas Head is a promontory 4 miles west of Padstow, jutting out into the sea from Trevose Head, and separated from it by an isthmus about 100 feet above sea-level, which is washed clear of soil by the ground seas which sweep over it from the north. The headland is 165 feet above sea-level at its highest point, and is almost as broad from north to south as it is long from east to west. The base and foreshore of the headland appear to be entirely composed of greenstone containing much calcite. The microscope shows it to be probably an altered dolerite.

Population Centers of the Rimac Valley of Peru

1954 ◽  
Vol 20 (2) ◽  
pp. 130-148 ◽  
Author(s):  
Louis M. Stumer
Keyword(s):  
Sea Level ◽  
North Coast ◽  
Central Coast ◽  
Easy Task ◽  
The North ◽  
Atypical Features ◽  
Peruvian Coast ◽  
Northern Peru ◽  
North Coast Of Peru

This Article is intended less as a descriptive piece on the archaeology of the Rimac Valley than it is as a single-valley application of various conclusions reached by Richard P. Schaedel in his Major Ceremonial and Population Centers in Northern Peru (1951). Schaedel, in a broad synthetic study of major ruins on the North Coast of Peru, comes to several interesting conclusions on the “urban revolution” in that region. The author, who was already engaged in a survey of the Rimac, with the focus on the coastal cultures from sea level to the 1000-meter line, felt impelled to shift the emphasis of his survey from straight description to a Central Coast application of Schaedel's North Coast findings. This was a fairly easy task, as the sites were already being analyzed both architecturally and ceramically.The Rimac, the “valley of Lima,” presents sufficient of both typical and atypical features of a Peruvian coastal valley to make the application of Schaedel's theories to a single valley at least fairly indicative of their validity for the entire Peruvian coast.

Postglacial relative sea-level change, Port au Port area, west Newfoundland

1985 ◽  
Vol 22 (7) ◽  
pp. 1039-1047 ◽  
Author(s):  
I. A. Brookes ◽  
D. B. Scott ◽  
J. H. McAndrews
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
High Water ◽  
Relative Sea Level ◽  
Radiocarbon Dates ◽  
Ice Load ◽  
Bay Area ◽  
Port Area ◽  
Minimum Age ◽  
Late Wisconsinan

We first report pollen and foraminifera analyses and radiocarbon dates from two cores taken from salt-marsh deposits bordering Port au Port Bay, southwestern Newfoundland. Results show that relative sea level (RSL) stood at 2.8 m below present higher high-water level (HHWL) at 2770 ± 300 years BP and at −1.8 m at 2365 ± 175 years BP at the core sites. They permit calculation of a rate of late Holocene RSL change from western Newfoundland. We then report other available dates bearing on the earlier RSL record of this area.A date of 5800 ± 200 years BP fixes the age of minimum RSL in Port au Port Bay at 11–14 m below present. A date of 9350 ± 120 years BP from St. George's provides a minimum age for the passage of sea level below present there. A date of 12 600 ± 140 years BP from Stephenville fixes a sea level at 29 m above present, whereas one of 13 600 ± 110 years BP from Abrahams Cove dates the marine limit at 44 m. These geographically restricted data closely constrain a curve of postglacial RSL change in the Port au Port Bay – northern St. George's Bay area. The form of the curve supports a recent model predicting sea-level response to wastage of a limited late Wisconsinan ice load in the wider region.

Late Glacial landforms of Wollaston Peninsula, Victoria Island, Northwest Territories: product of ice-marginal retreat, surge, and mass stagnation

1988 ◽  
Vol 25 (2) ◽  
pp. 262-279 ◽  
Author(s):  
David R. Sharpe
Keyword(s):  
Northwest Territories ◽  
Large Scale ◽  
Regional Scale ◽  
Late Glacial ◽  
Ground Moraine ◽  
Ice Conditions ◽  
Late Wisconsinan ◽  
Victoria Island ◽  
Glacial Landforms ◽  
Subglacial Meltwater

An analysis of glacial landforms on a regional scale leads to an interpretation of the dynamics of Late Wisconsinan glaciation on Wollaston Peninsula, Victoria Island, Northwest Territories. The glacial record is dominated by four adjacent belts of landforms: (I) ground moraine (till plains and ice-marginal drainage features), (II) hummocky moraine, (III) lateral and shear moraine, and (IV) streamlined landforms. The landform belts are considered as representing four distinct glacial ice conditions or regimes: (1) ice-margin retreat during extending flow of thin, active ice; (2) marginal ice stagnation following compressional flow; (3) a surging ice margin producing massive shear moraines; and (4) large-scale flooding and mass ice stagnation following a surge. These landform belts were arranged in zones by topographically controlled glacial dynamics, the latter two defining a former ice stream.Glaciological inferences can be extended by examining the sediments and processes that produced each landform set. Ground-moraine sediments were produced mainly subglacially from melt out or lodgment of glacial debris. Hummocky moraine resulted from debris flow and meltwater deposition controlled by ice, from resedimentation by sediment gravity flow, and from slump. Compressional shearing stacked thick deposits of drift prior to resedimentation. Simple lateral or end moraines may comprise interbedded sediment gravity flows deposited at static ice margins. Deformed lateral moraines resulted from intense marginal compressive flow that sheared and stacked thick, coarse sediment ridges or plates. This lateral shearing may be attributed to streaming or large ice surges. Drumlin exposures showed undeformed, interbedded, stratified sediments that appear to have accumulated in a subglacial cavity; there is no deformation related to high subglacial stress. Subglacial meltwater floods may have followed glacier surge. The greatly extended and thinner ice mass produced by the surge melted in place as clean (debris-free) ice.

scholarly journals Simulation of the Greenland Ice sheet over two glacial cycles: Investigating a sub-ice shelf melt parameterisation and relative sea level forcing in an ice sheet-ice shelf model

2017 ◽  
Author(s):  
Sarah L. Bradley ◽  
Thomas J. Reerink ◽  
Roderik S. W. van de Wal ◽  
Michiel M. Helsen
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Shelf ◽  
Temporal Behaviour ◽  
The North ◽  
Non Local ◽  
Continental Shelf Break

Abstract. Observational evidence, including offshore moraines and sediment cores confirm that at the Last Glacial maximum (LGM) the Greenland ice sheet (GrIS) grew to a significantly larger spatial extent than seen at present, grounding into Baffin Bay and to the continental shelf break. Given this larger spatial extent and it is close proximity to the neighboring Laurentide (LIS) and Innuitian Ice sheet (IIS), it is likely these ice sheets will have had a strong non-local influence on the spatial and temporal behaviour of the GrIS. Most previous paleo ice sheet modelling simulations recreated an ice sheet that either did not extend out onto the continental shelf; or utilized a simplified marine ice parametersiation and therefore did not fully include ice shelf dynamics, and or the sensitivity of the GrIS to this non-local signal from the surrounding ice sheets. In this paper, we investigated the evolution of the GrIS over the two most recent glacial-interglacial cycles (240 kyr BP to present day), using the ice sheet-ice shelf model, IMAU-ICE and investigated the influence of the LIS and IIS via an offline relative sea level (RSL) forcing generated by a GIA model. This RSL forcing controlled via changes in the water depth below the developing ice shelves, the spatial and temporal pattern of sub-ice shelf melting, which was parametrised in relation to changes in water depth. In the suite of simulations, the GrIS at the glacial maximums coalesced with the IIS to the north, expanded to the continental shelf break to the south west but remained too restricted to the north east. In terms of an ice-volume equivalent sea level contribution, at the Last Interglacial (LIG) and LGM the ice sheet added 1.46 m and −2.59 m to the budget respectively. The estimated lowering of the sea level by the Greenland contribution is considerably more (1.26 m) than most previous studies indicated whereas the contribution to the LIG high stand is lower (0.7 m). The spatial and temporal behaviour of the northern margin was highly variable in all simulations, controlled by the sub surface melt (SSM), which was dictated by the RSL forcing and the glacial history of the IIS and LIS. In contrast, the southwestern part of the ice sheet was insensitive to these forcing’s, with a uniform response in an all simulations controlled by the surface air temperature (SAT) forcing, derived from ice cores.

scholarly journals The Dynamics of Marine Ice Sheets

1979 ◽  
Vol 24 (90) ◽  
pp. 167-177 ◽  
Author(s):  
Robert H. Thomas
Keyword(s):  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ice Shelves ◽  
The North ◽  
West Antarctic ◽  
Grounding Line ◽  
Ice Sheet Dynamics

AbstractMarine ice sheets rest on land that, for the most part, is below sea-level. Ice that flows across the grounding line, where the ice sheet becomes afloat, either calves into icebergs or forms a floating ice shelf joined to the ice sheet. At the grounding line there is a transition from ice-sheet dynamics to ice-shelf dynamics, and the creep-thinning rate in this region is very sensitive to sea depth; rising sea-level causes increased thinning-rates and grounding-line retreat, falling sea-level has the reverse effect. If the bedrock slopes down towards the centre of the ice sheet there may be only two stable modes: a freely-floating ice shelf or a marine ice sheet that extends to the edge of the continental shelf. Once started, collapse of such an ice sheet to form an ice shelf may take place extremely rapidly. Ice shelves which form in embayments of a marine ice sheet, or which are partially grounded, have a stabilizing influence since ice flowing across the grounding line has to push the ice shelf past its sides. Retreat of the grounding line tends to enlarge the ice shelf, which ultimately may become large enough to prevent excessive outflow from the ice sheet so that a new equilibrium grounding line is established; removal of the ice shelf would allow retreat to continue. During the late-Wisconsin glacial maximum there may have been marine ice sheets in the northern hemisphere but the only current example is the West Antarctic ice sheet. This is buttressed by the Ross and Ronne Ice Shelves, and if climatic warming were to prohibit the existence of these ice shelves then the ice sheet would collapse. Field observations suggest that, at present, the ice sheet may be advancing into parts of the Ross Ice Shelf. Such advance, however, would not ensure the security of the ice sheet since ice streams that drain to the north appear to flow directly into the sea with little or no ice shelf to buttress them. If these ice streams do not flow over a sufficiently high bedrock sill then they provide the most likely avenues for ice-sheet retreat.

The last glaciation of Marvin Peninsula, northern Ellesmere Island, High Arctic, Canada

1989 ◽  
Vol 26 (12) ◽  
pp. 2578-2590 ◽  
Author(s):  
Donald S. Lemmen
Keyword(s):  
High Arctic ◽  
Ellesmere Island ◽  
North Coast ◽  
Radiocarbon Dates ◽  
The North ◽  
Last Glaciation ◽  
Ice Retreat ◽  
Late Wisconsinan ◽  
Glaciomarine Sediments ◽  
North And South

The limit of the last glaciation on Marvin Peninsula, northernmost Ellesmere Island, is recorded by extensive ice-marginal landforms and early Holocene glaciomarine sediments. While glaciers occupied most valleys on the peninsula, other areas remained ice free, as did most of the adjacent fiords. Beyond the ice limit, sparse erratics and degraded meltwater channels within weathered bedrock are evidence of older, more extensive glaciation(s). Shorelines and marine shells 50 m above the limit of the Holocene sea along the north coast relate to these older glacial events.Thirty-four new radiocarbon dates provide a chronology of ice buildup and retreat. Glaciers reached their limit after 23 ka, and locally as late as 11 ka. This was achieved by both expansion of existing glaciers and accumulation on plateau and lowland sites, which are presently ice free. Late Wisconsinan climate was characterized by cold and extreme aridity. Five dates ranging from 11 to 31 ka BP on subfossil bryophytes suggest that ice-free areas were biologically productive throughout the last glaciation. Ice retreat and postglacial emergence had begun by 9.5 ka and was associated with a marked climatic amelioration. The deglacial chronology confirms a pronounced disparity in the timing of ice retreat on the north and south sides of the Grant Land Mountains.

scholarly journals The Dynamics of Marine Ice Sheets

1979 ◽  
Vol 24 (90) ◽  
pp. 167-177 ◽  
Author(s):  
Robert H. Thomas
Keyword(s):  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ice Shelves ◽  
The North ◽  
West Antarctic ◽  
Grounding Line ◽  
Ice Sheet Dynamics

AbstractMarine ice sheets rest on land that, for the most part, is below sea-level. Ice that flows across the grounding line, where the ice sheet becomes afloat, either calves into icebergs or forms a floating ice shelf joined to the ice sheet. At the grounding line there is a transition from ice-sheet dynamics to ice-shelf dynamics, and the creep-thinning rate in this region is very sensitive to sea depth; rising sea-level causes increased thinning-rates and grounding-line retreat, falling sea-level has the reverse effect. If the bedrock slopes down towards the centre of the ice sheet there may be only two stable modes: a freely-floating ice shelf or a marine ice sheet that extends to the edge of the continental shelf. Once started, collapse of such an ice sheet to form an ice shelf may take place extremely rapidly. Ice shelves which form in embayments of a marine ice sheet, or which are partially grounded, have a stabilizing influence since ice flowing across the grounding line has to push the ice shelf past its sides. Retreat of the grounding line tends to enlarge the ice shelf, which ultimately may become large enough to prevent excessive outflow from the ice sheet so that a new equilibrium grounding line is established; removal of the ice shelf would allow retreat to continue. During the late-Wisconsin glacial maximum there may have been marine ice sheets in the northern hemisphere but the only current example is the West Antarctic ice sheet. This is buttressed by the Ross and Ronne Ice Shelves, and if climatic warming were to prohibit the existence of these ice shelves then the ice sheet would collapse. Field observations suggest that, at present, the ice sheet may be advancing into parts of the Ross Ice Shelf. Such advance, however, would not ensure the security of the ice sheet since ice streams that drain to the north appear to flow directly into the sea with little or no ice shelf to buttress them. If these ice streams do not flow over a sufficiently high bedrock sill then they provide the most likely avenues for ice-sheet retreat.

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