Geophysical evidence for a large Holocene ice marginal moraine of Skeiðarárjökull, SE Iceland

2020 ◽  
Author(s):  
Devin Harrison ◽  
Neil Ross ◽  
Andrew Russell ◽  
Stuart Jones
Keyword(s):  
Surface Morphology ◽  
Environmental History ◽  
Sea Level ◽  
Low Frequency ◽  
Ice Age ◽  
The Holocene ◽  
Geophysical Surveys ◽  
History Of ◽  
Ground Penetrating ◽  
Surface Geomorphology

<p>The sedimentary record of Icelandic ice-contact environments provides valuable information about glacier margin dynamics and position, relative sea-level and the geomorphic processes driving proglacial environments. This important archive has been little exploited, however, with most glacier and sea level reconstructions based on limited sedimentary exposures and surface geomorphic evidence. Although geophysical surveys of Icelandic sandur have been conducted, they have often been of limited spatial scale and focused on specific landforms. Here, we report an extensive (42 km of data) detailed low-frequency (40 and 100 MHz) ground-penetrating radar (GPR) survey of the Sandgigúr moraine complex, SE Iceland, which transforms our understanding of this landform, with implications for the Holocene history of Skeiðarársandur and SE Iceland.</p><p>The Sandgigúr moraines are located on Skeiðarársandur, SE Iceland, down-sandur of large Little Ice Age-moraines of Skeiðarárjökull. They have a relatively subtle surface geomorphic expression (typically 125 m wide and 7 m high), and knowledge of their formation is limited, with no dating control on their age or detailed geomorphic or sedimentological investigations.  GPR investigations reveal a much larger (60 m high and 1200 m wide) and extensive buried moraine complex than that suggested by surface morphology, suggesting that the moraine was a major Holocene ice margin of Skeiðarárjökull.</p><p>GPR reflections interpreted as large progradational foresets (up to 20 m in height) beneath the morainic structure are consistent with a sub-aqueous depositional environment before moraine formation, providing potential controls on former sea-level.  The GPR data also provide information on the internal structure of the moraine, with evidence for glacitectonism within the proximal side of the moraine, multiphase moraine formation, and possible buried ice at depth. A 30-40 m thick package of down-sandur dipping GPR reflections drape the leeside of the moraine, evidencing glaciofluvial deposition during and after moraine development. Potential moraine breaches, possibly caused by glaciofluvial (e.g. jökulhlaup) events, are also apparent within the GPR data and the surface geomorphology.</p><p>We combine GPR-derived subsurface architecture with the current surface morphology to develop a conceptual model detailing the geomorphic evolution of the moraines and surrounding region, from pre-moraine morphology, to their formation and breaching, resulting in the subsequent present-day morphology. These results provide new insights into the Holocene to present-day evolution of Skeiðarársandur and Skeiðarárjökull, with implications for reconstructions of the Holocene environmental history of SE Iceland.</p>

Palaeoenvironmental significance of a large-scale buried ice-marginal landsystem, Skeiðarársandur, SE Iceland

2021 ◽  
Author(s):  
Devin Harrison ◽  
Neil Ross ◽  
Andrew J. Russell ◽  
Stuart J. Jones
Keyword(s):  
Surface Morphology ◽  
Environmental History ◽  
Sea Level ◽  
Ice Age ◽  
Glacial History ◽  
Relative Sea Level ◽  
The Holocene ◽  
Geophysical Surveys ◽  
History Of ◽  
Dip Angle

<p>The sedimentary record of Icelandic ice-contact environments provides valuable information about glacier margin dynamics and position, relative sea-level, and the geomorphic processes that drive the evolution of proglacial environments. This important archive has been little exploited, however, with most glacier and sea level reconstructions based on limited sedimentary exposures and surface geomorphic evidence. Although geophysical surveys of Icelandic sandur have been conducted, they have often been of limited spatial scale and focus on specific landforms. We report an extensive (42 km of data within a 24 km<sup>2 </sup>study area) and detailed (reflections recorded at depths of up to 100 m) low-frequency (40 and 100 MHz) Ground-Penetrating Radar (GPR) survey of the Sandgígur moraine complex, SE Iceland. This transforms our understanding of this landform, with implications for the Holocene glacial history and evolution of Skeiðarársandur and SE Iceland.</p><p>The Sandgígur moraines are located on Skeiðarársandur, SE Iceland, down-sandur of large Little Ice Age-moraines of Skeiðarárjökull. They have a relatively subtle surface geomorphic expression (typically 7 m high and 125 m wide), and knowledge of their formation is limited, with no dating control on their age or detailed geomorphic or sedimentological investigations. GPR-data reveals reflections interpreted as large progradational foresets (dip angle: 2.19° – 6.87°) beneath the morainic structure (depth of 100 m). These features are consistent with a sub-aqueous depositional environment before moraine formation, providing potential indications of past relative sea-level limits. GPR profiles in the vicinity of the Sandgígur moraines reveal a much larger (67 m high and 1.25 km wide) and extensive buried moraine complex than that suggested by surface morphology. Indicating that the moraine was a major Holocene ice margin of Skeiðarárjökull. The buried Sandgígur moraine ridge is comprised of a unit of chaotic folded reflections adjacent to a unit of parallel, down-sandur dipping reflections (dip angle: 1.29° – 2.27°) indicative of an ice-contact or end-moraine fan. Possible evidence of buried ice at depth is also present within radargrams surrounding the moraine ridges. Sediment above the morainic bounding surface is interpreted to be dominated by glaciofluvial deposits with an estimated sediment volume of 1.04 km<sup>3</sup> over the 24 km<sup>2</sup> study area. Potential moraine breaches, possibly caused by high magnitude jökulhlaups (glacier outburst floods) are coincident within the GPR data and the surface geomorphology.</p><p>We combine GPR-derived subsurface architecture with the current surface morphology to develop a conceptual model detailing the geomorphic evolution of the moraines and surrounding region, from pre-moraine morphology, to their formation and burial, resulting in the present-day morphology. These results provide new insights into the Holocene to present-day glacial history of Skeiðarárjökull and the controls on sedimentation responsible for the evolution of Skeiðarársandur, with implications for the formation of sandar environments and the Holocene environmental history of SE Iceland.</p>

scholarly journals Neoglacial history of Robson Glacier, British Columbia

2017 ◽  
Vol 54 (11) ◽  
pp. 1153-1164 ◽  
Author(s):  
B.H. Luckman ◽  
M.H. Masiokas ◽  
K. Nicolussi
Keyword(s):  
British Columbia ◽  
Little Ice Age ◽  
Ice Age ◽  
Tree Line ◽  
Canadian Rockies ◽  
The Holocene ◽  
Forest Sites ◽  
History Of ◽  
Subfossil Wood ◽  
Glacier Advance

As glaciers in the Canadian Rockies recede, glacier forefields continue to yield subfossil wood from sites overridden by these glaciers during the Holocene. Robson Glacier in British Columbia formerly extended below tree line, and recession over the last century has progressively revealed a number of buried forest sites that are providing one of the more complete records of glacier history in the Canadian Rockies during the latter half of the Holocene. The glacier was advancing ca. 5.5 km upvalley of the Little Ice Age terminus ca. 5.26 cal ka BP, at sites ca. 2 km upvalley ca. 4.02 cal ka BP and ca. 3.55 cal ka BP, and 0.5–1 km upvalley between 1140 and 1350 A.D. There is also limited evidence based on detrital wood of an additional period of glacier advance ca. 3.24 cal ka BP. This record is more similar to glacier histories further west in British Columbia than elsewhere in the Rockies and provides the first evidence for a post-Hypsithermal glacier advance at ca. 5.26 cal ka BP in the Rockies. The utilization of the wiggle-matching approach using multiple 14C dates from sample locations determined by dendrochronological analyses enabled the recognition of 14C outliers and an increase in the precision and accuracy of the dating of glacier advances.

Holocene and latest Pleistocene fluctuations of Stutfield Glacier, Canadian Rockies

2001 ◽  
Vol 38 (8) ◽  
pp. 1141-1155 ◽  
Author(s):  
G D Osborn ◽  
B J Robinson ◽  
B H Luckman
Keyword(s):  
19Th Century ◽  
18Th Century ◽  
Late Glacial ◽  
Ice Age ◽  
Late 19Th Century ◽  
Canadian Rockies ◽  
The Holocene ◽  
The North ◽  
History Of ◽  
Glacier Advance

The Holocene and late glacial history of fluctuations of Stutfield Glacier are reconstructed using moraine stratigraphy, tephrochronology, and dendroglaciology. Stratigraphic sections in the lateral moraines contain tills from at least three glacier advances separated by volcanic tephras and paleosols. The oldest, pre-Mazama till is correlated with the Crowfoot Advance (dated elsewhere to be Younger Dryas equivalent). A Neoglacial till is found between the Mazama tephra and a paleosol developed on the Bridge River tephra. A log dating 2400 BP from the upper part of this till indicates that this glacier advance, correlated with the Peyto Advance, culminated shortly before deposition of the Bridge River tephra. Radiocarbon and tree-ring dates from overridden trees exposed in moraine sections indicate that the initial Cavell (Little Ice Age (LIA)) Advance overrode this paleosol and trees after A.D. 1271. Three subsequent phases of the Cavell Advance were dated by dendrochronology. The maximum glacier extent occurred in the mid-18th century, predating 1743 on the southern lateral, although ice still occupied and tilted a tree on the north lateral in 1758. Subsequent glacier advances occurred ca. 1800–1816 and in the late 19th century. The relative extent of the LIA advances at Stutfield differs from that of other major eastward flowing outlets of the Columbia Icefield, which have maxima in the mid–late 19th century. This is the first study from the Canadian Rockies to demonstrate that the large, morphologically simple, lateral moraines defining the LIA glacier limits are actually composite features, built up progressively (but discontinuously) over the Holocene and contain evidence of multiple Holocene- and Crowfoot-age glacier advances.

Holocene sea-level history of the Canadian Beaufort shelf

1993 ◽  
Vol 30 (1) ◽  
pp. 103-108 ◽  
Author(s):  
Philip R. Hill ◽  
Arnaud Héquette ◽  
Marie-Hélène Ruz
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Zone ◽  
Marine Sediments ◽  
Tidal Marsh ◽  
Relative Sea Level ◽  
The Holocene ◽  
Single Piece ◽  
History Of ◽  
Holocene Sea Level

New radiocarbon ages pertaining to the Holocene sea-level history of the Canadian Beaufort shelf are presented. The ages were obtained on samples of freshwater and tidal-marsh peat beds from offshore boreholes and shallow cores in the coastal zone and on molluscs and a single piece of wood deposited in foraminifera-bearing marine sediments. Although none of the samples record directly the position of relative sea level, the suite of ages constrains the regional curve sufficiently to suggest a faster rate of mid Holocene sea level rise (7–14 mm/a) than previously thought. The rate of relative rise slowed markedly in the last 3000 years, approaching the present at a maximum probable rate of 2.5 mm/a.

scholarly journals Gas Hydrate Formation and Dissipation Histories in the Northern Margin of Canada: Beaufort-Mackenzie and the Sverdrup Basins

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Jacek Majorowicz ◽  
Kirk Osadetz ◽  
Jan Safanda
Keyword(s):  
Sea Level ◽  
Canadian Arctic ◽  
Beaufort Sea ◽  
Ice Cover ◽  
Pressure Effects ◽  
Ice Age ◽  
Glacial Ice ◽  
The Holocene ◽  
Surface Temperatures ◽  
Gas Hydrate Formation

Gas hydrates (GHs) are a prominent subsurface feature on the Canadian Arctic continental margin. They occur both onshore and offshore, although they formed generally terrestrially, during the last glacial sea level low-stand, both in a region that was persistently glaciated (Queen Elizabeth Islands Group, Canadian Arctic Archipelago (QEIG)), and in a region that was not persistently glaciated (Mackenzie Delta-Beaufort Sea (MD-BS)). Parts of both regions were transgressed in the Holocene. We study the dynamic permafrost and GH history in both regions using a numerical model to illustrate how changes in setting and environment, especially periodic glacial ice cover, affected GH stability. MD-BS models represent the Mallik wellsite and these models successfully match current permafrost and GH bases observed in the well-studied Mallik wells. The MD-BS models show clearly that GHs have persisted through interglacial episodes. Lower surface temperatures in the more northerly QEIG result in an earlier appearance of GH stability that persists through glacial-interglacial intervals, although the base of GH base stability varies up to 0.2 km during the 100 ka cycles. Because of the persistent glacial ice cover QEIG models illustrate pressure effects attributed to regional ice sheet loading on the bases of both permafrost and GHs since 0.9 MYBP. QEIG model permafrost and GH depths are 572 m and 1072 m, respectively, which is like that observed commonly on well logs in the QEIG. In order to match the observed GH bases in the QEIG it is necessary to introduce ice buildup and thaw gradually during the glacials and interglacials. QEIG sea level rose 100–120 m about 10 ka ago following the most recent glaciation. Shorelines have risen subsequently due to isostatic glacial unloading. Detailed recent history modeling in QEIG coastal regions, where surface temperatures have changed from near zero in the offshore to −20°C in the onshore setting results in a model GH stability base, that is, <0.5 km. These coastal model results are significantly shallower than the inferred average GH base about 1 km in wells, Smith and Judge (1993). QEIG interisland channels are generally shallow and much of the previous shoreline inundated by the Holocene transgression was above the glacial sea level low-stand during the last ice age, resulting in a QEIG setting somewhat analogous to the relict terrestrial GH now transgressed by the shallow Beaufort Sea. It is also possible that the marine conditions were present at emergent shorelines for a shorter time or that the pretransgression subsurface temperatures persisted or were influenced by coastal settings, especially where lateral effects may not be well represented by 1D models.

Dating Climatic Episodes of the Holocene

1974 ◽  
Vol 4 (1) ◽  
pp. 9-24 ◽  
Author(s):  
Wayne M. Wendland ◽  
Reid A. Bryson
Keyword(s):  
Cultural History ◽  
Sea Level ◽  
Cultural Change ◽  
Climatic Impact ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
Independent Analysis ◽  
The World ◽  
History Of ◽  
Cultural Discontinuities

Monitoring evidence indicates that the Holocene embraced a sequence of rather discrete climatic episodes. The transitions between these environmental episodes apparently were abrupt and globally synchronous. This paper reports on statistical analyses of radiocarbon dates associated with environmental change and cultural change.Over 800 14C dates associated with pollen maxima and minima, sea level maxima and minima, and top and bottom surfaces of peat beds were simultaneously analyzed to identify times of globally synchronous environmental discontinuities.Some 3700 14C dates associated with 155 cultural continua of the world were collectively analyzed to identify worldwide synchroneities in appearance and termination of the cultures.Significant globally synchronous discontinuities were identified in each independent analysis. The dates of environmental and cultural discontinuities are rather similar, particularly during the recent half of the Holocene. The fact that the cultural discontinuities mostly follow rather closely those of the paleobotanical record suggests that there has been a distinct climatic impact on the cultural history of man.

Late Quaternary Climate and Vegetation of the Sudanian Zone of Northeast Nigeria

2002 ◽  
Vol 58 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Ulrich Salzmann ◽  
Philipp Hoelzmann ◽  
Irena Morczinek
Keyword(s):  
Environmental History ◽  
Late Pleistocene ◽  
Late Quaternary ◽  
Climatic Conditions ◽  
Lake Levels ◽  
The Holocene ◽  
Quaternary Climate ◽  
History Of ◽  
Sudanian Zone ◽  
Humid Period

AbstractThe Lake Tilla crater lake in northeastern Nigeria (10°23′N, 12°08′E) provides a ca. 17,000 14C yr multiproxy record of the environmental history of a Sudanian savanna in West Africa. Evaluation of pollen, diatoms, and sedimentary geochemistry from cores suggests that dry climatic conditions prevailed throughout the late Pleistocene. Before the onset of the Holocene, the slow rise in lake levels was interrupted by a distinct dry event between ca. 10,900 and 10,500 14C yr B.P., which may coincide with the Younger Dryas episode. The onset of the Holocene is marked by an abrupt increase in lake levels and a subsequent spread of Guinean and Sudanian tree taxa into the open grass savanna that predominated throughout the Late Pleistocene. The dominance of the mountain olive Olea hochstetteri suggests cool climatic conditions prior to ca. 8600 14C yr B.P. The early to mid-Holocene humid period culminated between ca. 8500 and 7000 14C yr B.P. with the establishment of a dense Guinean savanna during high lake levels. Frequent fires were important in promoting the open character of the vegetation. The palynological and palaeolimnological data demonstrate that the humid period terminated after ca. 7000 14C yr B.P. in a gradual decline of the precipitation/evaporation ratio and was not interrupted by abrupt climatic events. The aridification trend intensified after ca. 3800 14C yr B.P. and continued until the present.

Climate, fire, farming and the recent vegetation history of subantarctic Campbell Island

2007 ◽  
Vol 98 (1) ◽  
pp. 71-84 ◽  
Author(s):  
Matt McGlone ◽  
Janet Wilmshurst ◽  
Colin Meurk
Keyword(s):  
Sea Level ◽  
Little Ice Age ◽  
Vegetation History ◽  
Ice Age ◽  
Tundra Zone ◽  
Oceanic Climate ◽  
Tussock Grassland ◽  
History Of ◽  
Elevational Transect ◽  
Campbell Island

ABSTRACTCampbell Island is a small, uninhabited peat-covered island lying in the cool southern ocean 600 km south of the New Zealand mainland. Dracophyllum scrub is the main cover from sea level to 200 m, above which tussock grassland, macrophyllous forbs and tundra dominate. Seven peat profiles from sea level to the tundra zone provide an elevational transect for pollen and charcoal records spanning the last 500 years. Scrub density was relatively low between 200 and 400 cal yrs BP, possibly due to Little Ice Age cooling, but had recovered by the time Europeans discovered the island in AD 1810. Burning and grazing during a brief farming episode (AD 1895–1931) severely reduced scrub and palatable grasses and forbs. Vegetation recovery is now well advanced following cessation of farming and the later elimination of all feral grazing animals, cats and rats. Climates were cool in the southwest Pacific during the farming period, and since AD 1970 the island has warmed by c. 0·5°C. However, there has been no upwards movement of the scrubline despite vigorous regeneration of scrub at lower altitudes. The island's cloudy, highly oceanic climate appears to offset increasing summer warmth, and scrubline is likely to rise only if clearer and less windy, as well as warmer, summers eventuate.

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