Fossil Ice Wedges Research Articles

Detecting upland glaciation in Earth’s pre-Pleistocene record

Earth has sustained continental glaciation several times in its past. Because continental glaciers ground to low elevations, sedimentary records of ice contact can be preserved from regions that were below base level, or subject to subsidence. In such regions, glaciated pavements, ice-contact deposits such as glacial till with striated clasts, and glaciolacustrine or glaciomarine strata with dropstones reveal clear signs of former glaciation. But assessing upland (mountain) glaciation poses particular challenges because elevated regions typically erode, and thus have extraordinarily poor preservation potential. Here we propose approaches for detecting the former presence of glaciation in the absence or near-absence of ice-contact indicators; we apply this specifically to the problem of detecting upland glaciation, and consider the implications for Earth’s climate system. Where even piedmont regions are eroded, pro- and periglacial phenomena will constitute the primary record of upland glaciation. Striations on large (pebble and larger) clasts survive only a few km of fluvial transport, but microtextures developed on quartz sand survive longer distances of transport, and record high-stress fractures consistent with glaciation. Proglacial fluvial systems can be difficult to distinguish from non-glacial systems, but a preponderance of facies signaling abundant water and sediment, such as hyperconcentrated flood flows, non-cohesive fine-grained debris flows, and/or large-scale and coarse-grained cross-stratification are consistent with proglacial conditions, especially in combination with evidence for cold temperatures, such as rip-up clasts composed of noncohesive sediment, indicating frozen conditions, and/or evidence for a predominance of physical over chemical weathering. Other indicators of freezing (periglacial) conditions include frozen-ground phenomena such as fossil ice wedges and ice crystals. Voluminous loess deposits and eolian-marine silt/mudstone characterized by silt modes, a significant proportion of primary silicate minerals, and a provenance from non-silt precursors can indicate the operation of glacial grinding, even though such deposits may be far removed from the site(s) of glaciation. Ultimately, in the absence of unambiguous ice-contact indicators, inferences of glaciation must be grounded on an array of observations that together record abundant meltwater, temperatures capable of sustaining glaciation, and glacial weathering (e.g., glacial grinding). If such arguments are viable, they can bolster the accuracy of past climate models, and guide climate modelers in assessing the types of forcings that could enable glaciation at elevation, as well as the extent to which (extensive) upland glaciation might have influenced global climate.

Fossil Ice and Sand Wedges in South-Central Ulster, Northern Ireland

Spatial and temporal variations in the development of periglacial wedge structures in south-central Ulster. Northern Ireland can be related to climatic change during the earlier part of the late Glacial period. Ice wedges formed in the early stages of deglaciation (c.18,000 — 14,000 yrs B.P.) when cold and relatively humid periglacial conditions prevailed. Sand wedges formed during the later stages of deglaciation (c. 14,000 — 13,500 yrs B.P.?) and suggest a change to colder (?) and relatively drier climatic conditions.

Fossil Ice and Sand Wedges in South-Central Ulster, Northern Ireland

Spatial and temporal variations in the development of periglacial wedge structures in south-central Ulster. Northern Ireland can be related to climatic change during the earlier part of the late Glacial period. Ice wedges formed in the early stages of deglaciation (c.18,000 — 14,000 yrs B.P.) when cold and relatively humid periglacial conditions prevailed. Sand wedges formed during the later stages of deglaciation (c. 14,000 — 13,500 yrs B.P.?) and suggest a change to colder (?) and relatively drier climatic conditions.

Fossil ice wedges in Patagonia and their palaeoclimatic significance

Fossil ice wedges in Patagonia and their palaeoclimatic significance

Fossil patterned ground in southern Sweden

Abstract An account of observations of fossil ice wedge polygons at Hassleholm in the province of Skane (Scania) is presented. The polygons are very large, 35 × 65 m, and the pattern orthogonal. They were formed on the surface of a small glaciofluvial delta, when the inland ice receded from northern Skane during pre-Bolling time. Some ice-wedge casts in the distal part of the delta have been eroded in their upper parts. Several syngenetic fossil ice wedges and fossil ground surfaces with frost cracked stones and ventifacts indicate a rising water level in the Baltic Ice Lake. Large nonsorted circles are also present. It is possible that the circles were formed by thermokarst phenomena. A preliminary report is given of an inventory of fossil frost fissures in southern Sweden. The paleoclimatic environment there at the time of recession of the inland ice is discussed.

SOIL TONGUES IN THE LEAMINGTON MORAINE, ONTARIO

Wedge-shaped soil structures occur in many parts of southern Canada and the northern United States. These have usually been interpreted as being ice-wedge casts. Yehle (1954), however, has expressed concern over the confusion of fossil ice wedges with features he termed soil tongues, but also referred to as soil pendants (Wright 1961) or podsolschornsteine (Johnsonn 1959). Not only are soil tongues superficially similar to ice-wedge casts, but they also occur in temperate latitudes which may have experienced periglacial conditions during the Pleistocene. Soil tongues, however, are solutional features, formed by rainwater percolating through unconsolidated calcareous deposits. They may be distinguished from ice-wedge casts and other wedge-shaped structures by: (a) the presence of pebble or other marker beds extending unbroken across the wedges; (b) the absence of bed contortions or pressure features in the materials adjacent to the wedges; (c) their conical three-dimensional shape; and (d) the lower carbonate content in the sediments of the wedges than in the surrounding materials.

The periglacial environment of Great Britain during the Devensian

The main question considered is the extent to which extra-glacial Britain had a permafrost environment in the Devensian, so the three features used in identifying contemporary permafrost are discussed. These are ice wedge polygons, pingos and thaw lakes. As their environments have been studied estimates of temperatures may be made when they are found in a Devensian context. A theoretical case can be made for regarding some involutions as representing the former active layer of permafrost but they have not been related to a contemporary environment. They cannot therefore give a measurement of Devensian conditions. Fossil ice wedges are very widespread in Great Britain, being found from the English Channel to the Scottish Highlands, and associated with late Early, Middle and Late Devensian deposits. Today ice wedges grow in continuous permafrost where the mean annual air temperature is — 6 to — 8 °C or lower. Remains of pingos of the open system type which today develop in discontinuous permafrost with a mean annual air temperature of — 3 to — 6 °C, are found in Wales and East Anglia. These continued to form until the end of the Younger Dryas, and indicate that discontinuous permafrost in England and Wales thawed completely only with the beginning of the Flandrian. The pingos must have begun to form after the transition from continuous to discontinuous permafrost, which probably took place with the rise in temperatures ahead of the Allerød. The area of continuous permafrost and ice wedge formation in Alaska is almost limited to the tundra. Apart from the coastal zone, discontinuous permafrost carries boreal forest with mean July air temperatures of around 15 °C, so that periods of tree growth in the Devensian do not necessarily imply the temporary disappearance of permafrost. Continuous permafrost in southern England implies a minimum fall in mean annual air temperatures of 16-17 °C, and a fall in the July mean of 4-5 °C. During the maximum ice advance the fall in mean annual air temperatures is estimated to be as much as 25 °C, with a fall in the July mean of 10 °C.

Periglacial Features Indicative of Permafrost: Ice and Soil Wedges

Ice wedges are wedge-shaped masses of ice, oriented vertically with their apices downward, a few millimeters to many meters wide at the top, and generally less than 10 m vertically. Ice wedges grow in and are confined to humid permafrost regions. Snow, hoar frost, or freezing water partly fill winter contraction cracks outlining polygons, commonly 5–20 m in diameter, on the surface of the ground. Moisture comes from the atmosphere. Increments of ice, generally 0.1–2.0 mm, are added annually to wedges which squeeze enclosing permafrost aside and to the surface to produce striking surface patterns. Soil wedges are not confined to permafrost. One type, sand wedges, now grows in arid permafrost regions. Sand wedges are similar in dimensions, patterns, and growth rates to ice wedges. Drifting sand enters winter contraction cracks instead of ice. Fossil ice and sand wedges are the most diagnostic and widespread indicators of former permafrost, but identification is difficult. Any single wedge is untrustworthy. Evidence of fossil ice wedges includes: wedge forms with collapse structures from replacement of ice; polygonal patterns with dimensions comparable to active forms having similar coefficients of thermal expansion; fabrics in the host showing pressure effects; secondary deposits and fabric indicative of a permafrost table; and other evidence of former permafrost. Sand wedges lack open-wedge, collapse structures, but have complex, nearly vertical, crisscrossing narrow dikelets and fabric. Similar soil wedges are produced by wetting and drying, freezing and thawing, solution, faulting, and other mechanisms. Many forms are multigenetic. Many socalled ice-wedge casts are misidentified, and hence, permafrost along the late-Wisconsinan border in the United States was less extensive than has been proposed.

Evidence of Fossil Ice Wedges in Early Weichselian Deposits at Foss-Eikjeland, Jæren, South-West Norway

A brief description is given of the stratigraphy of two gravel pits. The succession, in ascending order, consists of thick outwash-plain deposits followed by a lower till, a primary marine clay, and an upper till. Fossil ice wedges and a fossil kettle hole occur in the glaciofluvial sediments. These are described and their probable origin discussed. While the glaciofluvial deposits and the lower till probably represent Early Weichselian sediments, the marine clay is thought to be a Middle Weichselian interstadial. The upper till is from the last main phase of the Weichselian.

Fossil Cryonival Features in Central Wales

The areal distributions of various fossil cryonival features, soliflucted till, stratified screes, block fields, tors and nivation hollows are described from a glaciated area of central Wales, at an altitude of 200 to 600 m. Cryonival structures, such as fossil ice wedges and involutions, which occur in numerous deposits, are also briefly discussed. The importance of various geological, geomorphological and meteorological factors, which exert differing degrees of control over the actual distributions of these features, is stressed. In the major valleys a distinct spatial association of the various deposits is apparent, probably the result of progressive deglaciation of the region. A Late-Glacial age is proposed for most of the features considered.

Evidence of Sub-Till Sediments from a Weichselian Interstadial in the Gudbrandsdalen Valley, Central East Norway

The authors point out several localities with sub-till sediments in the highly ice-eroded Gudbrandsdalen Valley. Two localities are described and discussed. Based upon studies of texture and structure, the sediments are interpreted as proglacial deposits, not removed by a later ice-advance. The assumed permafrost structures (fossil ice wedges) and 6 finds of mammoth remnants, of which one has been C14 dated to 24,400 ± 900 years B. P. (Heintz 1969), indicate that these sediments are of an interstadial age.Tentatively this is named the Gudbrandsdalen interstadial. Out of the total of 15 mammoth finds in Norway, 13 are from the Gudbrandsdalen area. The sub-till sediments were presumably the depositaries for these fossils during the latest glaciation.

Intraformational Periglacial Structures in the Nose Hill Gravels and Sands, Calgary, Alberta, Canada

A gravel and sand sequence at Calgary, Alberta, resting unconformably on Paskapoo sandstone and overlain by a late Wisconsin till, has within it two distinct horizons of structures attributable to periglacial activity. The lower horizon shows involutions and deranged and frost-shattered pebbles, while the upper horizon shows fossil ice wedges. A periglacial environment probably existed in southwestern Alberta at least twice during the gravel and sand deposition, and the sequence is probably of Pleistocene age, although predating the earliest Laurentide ice advance in the area. The average annual temperature in the Calgary area was approximately 9°-14° C. cooler than at present.

Fossil Ice Wedges in Hampshire

THREE large fossil ice wedges have been discovered in a coastal section exposed at Highcliffe in Hampshire (M.R. 215931). They are to be found within the Plateau Gravel in the uppermost part of the cliff at about 100′ O.D. Here 2.4 m of gravels rest on Barton Beds, at this point consisting of an impermeable glauconitic clay. On top of the gravels is an uneven layer of brown loam up to 80 cm thick.

Eine begrabene Solifluktionsdecke und ihr Einfluß auf die heutige Vegetation: Beobachtungen auf einer Bliesterterrasse (Saarland)

Abstract. In the lower Blies valley the author discovered a periglacial mudflow consisting of white marl and fragments of limestone, surmounted by 25-30 cm river-sand belonging to a Riß-terrace. The surface of these deposits was covered by fossil ice-wedges. The changes in the phyto-sociological structure of the vegetation cover permitted to fix the exact extension of the periglacial mudflow.

Periglacial Structures in the Saskatchewan Gravels and Sands of Central Alberta, Canada

The Saskatchewan gravels and sands are composed dominantly of quartzitic sandstones, chert, and arkosic sandstones, together with a few fragments of basic volcanic rock, limestones and bedrock of local derivation. They have been recognized widely throughout the plains of western Canada and northwestern United States, everywhere lying unconformably upon bedrock and invariably being covered by glacial drift. Ages from late Tertiary to early Pleistocene have been suggested for these gravels and sands. Near Edmonton, Alberta, temporary exposures in a gravel pit revealed structures in the Saskatchewan gravels and sands that are attributed to deformation by frost action. These structures are: (1) a zone of deranged pebbles, (2) involutions, and (3) fossil ice wedges, now full of sand. The conclusions drawn from this study are: (1) a periglacial climate existed in central Alberta before the arrival of the Keewatin ice that deposited the Wisconsin till; (2) the Saskatchewan gravels and sands discussed here were d...

Intersecting Minor Ridges and Periglacial Features in the Lake Agassiz Basin, North Dakota

Low, intersecting ridges, 3-10 feet high and 75-500 feet wide, with intervening depressions form a fracture pattern which is strikingly revealed on airplane photos of the flat Lake Agassiz plain. The ridges occupy the axial part of the old lake basin and are known to extend from Fargo, North Dakota, northward to well beyond the Canadian boundary. Because the ridges are composed entirely of the underlying lake clays and surface soils, they cannot be explained by ordinary agents, such as wind, waves and currents, or glaciers. It is proposed that the ridges represent frozen-ground structures formed during retreat of the late Wisconsin ice. This is supported by the occurrence of periglacial involutions, fossil ice wedges, and polygonal and network soil patterns in the lake sediments.