Drumlins Research Articles

Sedimentary bodies, forms and occurrences in the Tudorevo and Mirovo glacial deposits of northern Velebit (Croatia)

A small glacier of cirque-valley type existed during the Late Pleistocene Wurm Glacial in the Tudorevo and Mirovo karst valleys of Northern Velebit. Its source was in Tudorevo, and it moved through Dundovic Mirovo and Bilensko Mirovo to Baricevic Dolac, shaping U-valleys around 4 km in length. After melting, glacial deposits remained, composed of chaotic and unsorted till, composed of carbonate sand, debris and sub-rounded clasts, cobbles and blocks of predominantly Middle Jurassic and subordinately Lower Jurassic carbonate rocks. In Dundovic Mirovo and Bilensko Mirovo, where the largest masses of glacial deposits occur, terminal and recessional moraines can be found over the ground moraine, as well as some other features, mostly drumlins (drumlin field), eskers, erratic blocks, kettle holes and striations. Some erratics have been transported for more than 4 km from their primary outcrops, e.g. clasts of Lower Jurassic Toarcian Spotty limestone. A terminal moraine was deposited between Bilensko Mirovo and Baricevic Dolac, perpendicular to the glaciated U-valley and it forms the Bilo hill, the northern and southern foothills of which are composed partly of glaciofluvial deposits. Between Tudorevo and Mirovo, a recessional moraine occurs above the ground moraine. The glacier was subject to polyphase melting and freezing, and the youngest freezing events may be related to cirques in Tudorevo. During melting events, glacier lakes are supposed to have existed, initially in the Baricevic Dolac, later in Mirovo area and finally in Tudorevo. These discharged into the karst underground by percolation through till and by erosion to the karstified underlying Middle Jurassic carbonates.

Late Glacial vegetation, sedimentation and ice recession chronology in the surroundings of Lake Prossa, central Estonia

Pollen records from Lake Prossa, located in the Saadjarv Drumlin Field, indicate rather homogeneous pollen spectra in the pre-Allerod period and a thick sediment sequence suggesting high input of mineral matter and erosion. This period is characterized by pioneer vegetation with dwarf-shrubs. At the beginning of the Allerod, Salix, Artemisia and redeposited temperate and thermophilous taxa prevailed in pollen spectra, referring to shrub tundra conditions, followed later by Betula and Pinus(?) arrival. Silt with organic debris deposited. Vegetational set-back and tundra plant species with scattered birches and silty deposits containing abundantly Drepanocladus fragments characterize the Younger Dryas stadial. The sedimentation rate decreased markedly and was followed by a hiatus at the beginning of the Holocene. The AMS 14 C dates, and microfossil and sedimentological data show that the ice front receded and stratified sediments started to deposit about 14 200-14 300 cal yr BP, permitting specification of poorly constrained ice recession chronology in central Estonia.

Ground-penetrating radar study of the Rahivere peat bog, eastern Estonia

The current case study presents results of the ground-penetrating radar (GPR) profiling at one of the Saadjarve drumlin field interstitial troughs, the Rahivere bog, eastern Estonia. The study was conducted in order to identify the bog morphology, and the thickness and geometry of the peat body. The method was also used to describe the applicability of GPR in the evaluation of the peat deposit reserve as the Rahivere bog belongs among the officially registered peat reserves. Fourteen GPR profiles, ~ 100 m apart and oriented perpendicular to the long axis of the depression, covering the bog and its surrounding areas, were acquired. In order to verify the radar image interpretation as well as to evaluate the velocity of electromagnetic waves in peat, a common source configuration was utilized and thirteen boreholes were drilled on the GPR profiles. A mean value of 0.036 m ns -1 corresponding to relative dielectric permittivity of 69.7 was used for the time-depth conversion. Radar images reveal major reflection from the peat-soil interface up to a depth of about 4 m, whereas drillings showed a maximum thickness of 4.5 m of peat. Minor reflections appear from the upper peat and mineral soil. According to the borehole data, undecomposed peat is underlain by decomposed one, but identifying them by GPR is complicated. Mineral soil consists of glaciolimnic silty sand in the peripheral areas of the trough, overlain by limnic clay in the central part. The calculated peat volumes (1 200 000 m 3 ) were found to exceed the earlier estimation (979 000 m 3 ) that was based solely on drilling data. Ground-penetrating radar, as a method that allows mapping horizontal continuity of the sub-peat interface in a non-destructive way, was found to provide detailed information for evaluating peat depth and extent.

Active drumlin field revealed at the margin of Múlajökull, Iceland: A surge-type glacier

ABSTRACT Recent marginal retreat of Mulajokull, a surge-type outlet glacier of Hofsjokull, Iceland, has revealed a drumlin fi eld consisting of more than 50 drumlins. The drumlins are 90–320 m long, 30–105 m wide, 5–10 m in relief, and composed of multiple beds of till deposited by lodgment and bed deformation. The youngest till layer truncates the older units with an erosion surface that parallels the drumlin form. Thus, the drumlins are built up and formed by a combination of subglacial depositional and erosional processes. Field evidence suggests each till bed to be associated with individual recent surges. We consider the fi eld to be active in the sense that the drumlins are shaped by the current glacial regime. The Mulajokull fi eld is the only known active drumlin fi eld, and is therefore a unique analogue to Pleistocene drumlin fi elds.

The planar shape of drumlins

The asymmetry of the planar shape of drumlins is an established paradigm in the literature and characterizes drumlins as resembling tear drops with a blunt (bullet-shaped) stoss end and a tapering (pointed) lee end. It is widely cited and never been seriously questioned. In this paper, the planar shape of 44,500 drumlins mapped in various regional settings from drumlin fields in North America and Northern Europe were objectively analysed by means of Geographic Information System tools. Two parameters were considered. The first (denoted here as As pl) focuses on the relative position of the point of intersection between the axes of the maximum length and the maximum width. It is defined as the distance between the upstream (i.e. beginning of the drumlin) and the intersection point (measured along the longitudinal axis) divided by the entire length of the long axis. Results indicate that the intersection point of the majority of drumlins (64%) is very close to the longitudinal midpoint (0.33 < As pl < 0.66). The second parameter ( As pl _A ) is defined as the ratio between the area of the upstream half of the drumlin to that of the entire drumlin. Results show that for most drumlins (81%), the upper half area is almost as large as the down-half (0.45 < As pl _A < 0.55). Taken together, these results concordantly indicate that drumlin planar shape has a strong tendency to be longitudinally symmetric and that the long-established paradigm of their plan form is false.

Проискождение друмлинов около збуйно (Центральная Польша)

Drumlins at Zbojno, Dobrzyn Lakeland, are located in a channel-like terminal basin, in the proximal part of the Chrostkowo end moraines. A fragment of the drumlin fi eld was examined in detail. Th e drumlins are elongated ridges, parallel to one another and to the basin margins. Th eir orientation is parallel to perpendicular with regard to the presumed regional direction of the ice sheet advance. Th e drumlins’ geological structure is tripartite, including a lower till, a glaciofl uvial core and a covering upper till. Georadar examination indicated the presence and extension of glaciotectonic deformations of the lower till. It is squeezed up to 3 m above its primary setting and forms protodrumlins that have not been, however, the bed bumps that stimulated a lee-side deposition. Protodrumlins are usually absent along a drumlin axis, but they occur also in pairs. Th ey could both initiate but also terminate drumlin development when thawing appeared in the subglacial zone and the ice body was disintegrated into dead-ice blocks. Glaciofl uvial cores are less deformed than the lower till: their sediments are stratifi ed, but commonly uplift ed towards a protodrumlin.

Glacial geomorphology in Utsjoki, Finnish Lapland proposes Younger Dryas fault-instability

Northern Fennoscandia has experienced high-magnitude postglacial fault (PGF) events, yet the role of seismic tremors in subglacial deformations and meltwater discharge has remained obscure. We studied glacial geomorphology in Utsjoki, Finnish Lapland, an area characterized by the Utsjoki drumlin field fanning out north and northeast to the Younger Dryas End Moraines (YDEMs) in northern Norway. Paleolandslides were common on fells (i.e. mountains shaped by Pleistocene glaciations) and were formed in nunatak position evidencing fault-instability in app. 11,900 calibrated (cal) BP. An anastomosing network of eskers was found throughout Utsjoki, and was probably generated through short-lived sliding bed stages during the discharge of subglacial lake(s). The formation of networks is different from time-transgressive evolution of single-ridged eskers in arborescent (treelike) systems. The most probable triggering mechanism for the meltwater outburst(s) was an earthquake tremor(s) associated with fault-instability during the late and post-Younger Dryas (YD). The alignment of the esker network was inconsistent with parallel-to-iceflow streamlining and the eskers erode or superimpose drumlins. Hence the esker network post-dates the streamlining. In some cases, hummocky (Pulju) moraine was observed to coexist with esker network and peculiar ‘kettle’ and ‘liquefaction’ features. We propose that glacio-seismotectonic events contributed not only to landslides but were also the primary force behind subglacial evolution of esker networks and possibly even hummocky moraine.

Geospatial analysis of controls on subglacial bedform morphometry in the New York Drumlin Field – implications for Laurentide Ice Sheet dynamics

AbstractThe outline and trend of 6566 subglacial bedforms in the New York Drumlin Field have been digitized from digital elevation data. A spatial predictive model has been used to extend values of bedform elongation over an area measuring 200 km × 110 km. The resulting surface is used in conjunction with depth‐to‐bedrock data and an assumed duration of ice residence to test three proposed controls on bedform elongation. Upon comparison, the resulting display of morphometry is best explained by differences in ice velocity across the field of study. The existence of multiple zones of fast‐moving ice located along the southern margin of the Laurentide Ice Sheet is implied by the observed patterns of bedform elongation and orientation. We present two interpretations that are consistent with the observations. First, enhanced basal sliding caused by decreasing effective pressure near a calving margin is suggested as a possible mechanism by which localized fast ice flow is initiated and maintained. Second, topographically controlled ice streams likely occupied the fjord‐like troughs of the Appalachian Upland northern rim. Contrary to previous understanding of the Laurentide southern margin in New York State, the resulting palaeoglaciological reconstruction illustrates a dynamic mosaic of ice stream and/or outlet glacier activity. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Quantitative assessment of the hydraulic role of subglaciofluvial interbeds in promoting deposition of deformation till (Northern Till, Ontario)

The Northern Till is a thick (>65 m) deformation till underlying some 7500 km 2 of Southern Ontario, Canada including the Peterborough Drumlin Field. It was deposited below the Lake Ontario ice stream of the Laurentide Ice Sheet. The till rests on glaciotectonized aquifer sediments and consists of multiple beds of till up to 6 m thick. These are separated by boulder lags, sometimes in the form of striated pavements, with thin (<30 cm) interbeds of poorly sorted waterlaid sand. The composite till stratigraphy indicates ‘punctuated aggradation’ where the subglacial bed was built up incrementally by the repeated ‘immobilization’ of deforming overpressured till layers. Boulders and sands indicate pauses in subglacial aggradation marked by sluggish sheet flows of water that reworked the top of the underlying till. Interbeds are laterally extensive and correlated using downhole electrical conductivity, core recovery and natural gamma data. A 3-D finite element model (FEFLOW) using data from 200 cored and geophysically logged boreholes, and a large digital water well dataset of 3400 individual records shows that the till functions as a ‘leaky aquitard’ as a consequence of water flow through interbeds. It is proposed that interbeds played a similar role in the subglacial hydraulic system below the Laurentide Ice Sheet by allowing drainage of excess porewater pressures in deforming sediment and promoting deposition of till. This is in agreement with theoretical studies of deforming bed dynamics and observations at modern glaciers where porewater in the deforming layer is discharged into underlying aquifers. In this way, the presence of interbeds may be fundamental in retarding downglacier transport of deforming bed material thereby promoting the build-up of thick subglacial till successions.

Landscape Ecological Structure in the Eastern Part of the North Vidzeme Biosphere Reserve, Latvia

Landscape Ecological Structure in the Eastern Part of the North Vidzeme Biosphere Reserve, Latvia Latvia is a country where the forest area has increased and habitat fragmentation has reversed compared with many other European countries. In order to examine the effect of this expansion on biodiversity, vegetation maps dating from 2002 and the years 1930-1936 were used for comparative landscape structure analyses while archive materials from forest plans, and data from the national forest management database were used for land use analysis. Four landscape ecoregions in the eastern side of the North Vidzeme Biosphere Reserve were selected for analysis. Landscape structure indicators derived from landscape ecology were used for the ecological assessment of land use changes. The total number of forest patches had decreased over the study period, but mean patch size had increased for all types of landscape element. This general change was found to vary between different landscape units in the study area. The biggest change in the area of forest patches occurred in the Rūjiena drumlin field, where the amount of forest patches decreased least and forest area increased the most. This study showed that the internal structure of the forest matrix changed substantially. This finding has implications for biodiversity protection if this trend of land use change continues.

Subglacially Formed Dunes with Bimodal and Graded Gravel in the Trenton Drumlin Field, Ontario

On fait ici la description de grandes structures sédimentaires du lit, soit des dunes graveleuses, que l'on trouve dans un site situé entre les drumiins du champ de drumiins de Trenton. Ces formes asymétriques et regroupées, qui font jusqu'à 10 m de haut, renferment d'importantes stratifications entrecroisées. Les dunes graveleuses occupent des conduits sous-glaciaires et sont souvent associées aux eskers. La structure interne des dunes laisse voir des surfaces de réactivation comme celles qui ont été décrites pour les structures sédimentaires en milieux éolien, marin et fluviatile. Les lits frontaux distincts et granoclassés sont caractérisés par une diminution verticale de la taille des matériaux grossiers, accompagnée soit d'une augmentation de la taille des particules de la matrice, soit d'une diminution du volume matriciel. Ces relations s'expliquent par le tri longitudinal de la charge de fond et le dépôt des particules en suspension dans la zone de division du courant formée du côté abrité de la dune. Les sédiments plus fins, surtout du sable, se trouvent en aval des dunes. Des matériaux provenant de la charge de fond et du transport des particules en suspension sont accumulés dans les lits en avant des dunes et ce, en fonction de la position par rapport à l'emplacement du point de raccordement du vortex de séparation. On croit que les dunes ont été formées dans des conduits sous-glaciaires sous des courants d'une profondeur de plusieurs dizaines de mètres.

Reconstructions of the Late Devensian (Dimlington Stadial) British-Irish Ice Sheet: the role of the upper Tees drumlin field, north Pennines, England

SUMMARY It has long been known that the upland areas of the Pennines, northern England, were a local ice source during the Late Devensian (Dimlington Stadial) glaciation of Britain. However, there has been little detailed work on their significance for ice sheet reconstructions. The presence of drumlins at high elevations within the northern Pennines is reported from the upper reaches of the Tees valley and Harwood Beck. Geomorphological mapping has identified 134 drumlins occurring up to an elevation of 662 m OD in association with superimposed drumlins and drift tails. These landforms, particularly the presence of superimposed forms, enable the reconstruction of two ice flow events associated with a local ice centre that formed during the Late Devensian glaciation in northern England. The earlier flow event was directed straight down the upper Tees valley from a limited source area on the high ground to the east of Cross Fell. The later event indicates a flow direction more transverse to the valley, from a more extensive source area that had migrated and expanded westwards across the high plateau of Cross Fell and southwards towards Dufton Fell. The presence of drumlins at this high altitude indicates sufficient ice thickness to allow basal deformation and suggests that drumlin upper elevation defines a thermal regime above which the plateau ice field was cold based and frozen to the bed. This requires the area to be completely covered by ice. This study demonstrates the importance of these upland areas in detailed reconstructions of a multi-domed, British-Irish Ice Sheet (BIIS).

Supporting evidence from the New York drumlin field that elongate subglacial bedforms indicate fast ice flow

Although drumlins and other subglacial bedforms are well‐studied features, controls on their formation and morphometry have remained elusive. Of current interest is the hypothesis that elongate bedforms (length:width ratios≥ 10) indicate fast ice flow, and perhaps the location of past ice streams. This hypothesis is explored by analysing drumlins from the New York State drumlin field. A subset of 548 drumlins between Oneida Lake and Lake Ontario was digitized using 10‐m grid cell digital elevation data. Because bedform elongation is greatest along the axis of a reconstructed lobe and increases down flowline, elongate bedforms are best explained by fast ice flow. The swath of elongate bedforms between lakes Ontario and Oneida, the boundaries of which do not coincide with topography, may signify the location of an ice stream during deglaciation.

Supporting evidence from the New York drumlin field that elongate subglacial bedforms indicate fast ice flow

Supporting evidence from the New York drumlin field that elongate subglacial bedforms indicate fast ice flow

Water-level changes and palaeogeography of proglacial lakes in eastern Estonia: synthesis of data from the Saadjärve Drumlin Field area

Water-level changes and palaeogeography of proglacial lakes in eastern Estonia: synthesis of data from the Saadjärve Drumlin Field area

Origin of drumlins on the floor of Lake Ontario and in upper New York State

Upper New York State, USA contains one of the largest drumlin fields (12,000 km 2) on the North America continent consisting of some 10,000 drumlins located between Lake Ontario in the north and the Finger Lakes; drumlin-like bedforms have also recently been discovered in deep water (∼ 200 m) on the nearby floor of the Rochester Basin in Lake Ontario. The New York State drumlin field was produced under the Laurentide Ice Sheet 18,000 years ago when it extended southwards to terminate against the Allegheny Plateau. Outcrops of drumlin cores exposed by erosion along the Lake Ontario shoreline provide windows into the stratigraphy and sedimentology of the northern part of the field. Sedimentological description of 10 coastal drumlin cores, combined with quantitative morphometric analysis of 1487 drumlins, shows that they are the product of subglacial erosion of till sheets separated by glaciolacustrine deposits. A two-phase subglacial model for drumlin formation is suggested consisting of initial aggradation of extensive till deposits during ice advance followed by erosion and streamlining possibly accompanying stillstand of the ice margin and building of moraines. Systematic changes in drumlin morphometry and spacing are evident, ranging from small numbers (< 15% of total bedforms) of widely separated, spindle-shaped forms (Length/Width ratios between 6 and 18) to more numerous (< 40%) broader forms (L/W ratios between 3 and 6) to most numerous (> 60%) closely spaced, ovoid drumlins (L/W ratios between 1 and 3). Drumlin shape appears to be systematically related to sediment thickness available for erosional streamlining; elongate spindle forms occur on the crests and lee sides of bedrock escarpments where sediment cover is thin. Larger ovoid drumlins occur in topographic depressions where sediment thickness is greater. Offshore streamlined forms on the floor of the deep water Rochester Basin in Lake Ontario have long axes at right angles to the trend of onshore drumlins. These are composed of rock (rock drumlins) and have an orientation structurally controlled by a newly identified inlier of Proterozoic Grenville Province metasediments.

The internal sediment architecture of a drumlin, Port Byron, New York State, USA

An exposure within the central portion of a large drumlin at Port Byron, New York State, USA, part of the large New York drumlin field, reveals a sequence of steeply dipping cemented sands and gravels of proglacial, ice-contact deltaic origin overlain by a thin till veneer. The sands and gravels appear to have been deposited within the proximal proglacial environment during a late retreat phase of the Laurentide Ice Sheet sometime prior to being overridden by subsequent ice and drumlinized. During deposition of the ice-contact delta, escaping subglacial regelation-meltwater permeated the proximal deltaic sediment pile and calcium carbonate was released, in a series of pulses, to form pore-occluding calcite cement within the sand and gravel porespaces. The calcium carbonate precipitated into the sands and gravels due to a reduction in hydrostatic pressure and CO2 outgassing of the meltwater as it exited from beneath the ice sheet. Once cemented, these deltaic sediments were considerably stronger and acted afterward as an obstacle around which the future ice advance streamed and, in turn, produced the characteristic drumlin shape. In overriding the ice-contact deltaic sediments, the ice sheet emplaced a thin layer of till which exhibits syndepositional deformation features indicative of being emplaced as a deforming bed layer beneath the advancing ice sheet. Micromorphological analysis of the overlying till shows that no interstitial or intraclastic calcite occurs within the till.

Influence of bedrock permeability and till grain size on the formation of the saadjärve drumlin field, Estonia, under an east-Baltic Weichselian ice stream

BoreasVolume 32, Issue 1 p. 167-177 Free to Read Influence of bedrock permeability and till grain size on the formation of the saadjärve drumlin field, Estonia, under an east-Baltic Weichselian ice stream MARIS RATTAS, MARIS RATTASSearch for more papers by this authorJAN A. PIOTROWSKI, JAN A. PIOTROWSKISearch for more papers by this author MARIS RATTAS, MARIS RATTASSearch for more papers by this authorJAN A. PIOTROWSKI, JAN A. PIOTROWSKISearch for more papers by this author First published: 09 October 2008 https://doi.org/10.1080/03009480310001849Citations: 35AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume32, Issue1March 2003Pages 167-177 RelatedInformation

Signature of the Baltic Ice Stream on Funen Island, Denmark during the Weichselian glaciation

Ice streams are major dynamic elements of modern ice sheets, and are believed to have significantly influenced the behaviour of past ice sheets. Funen Island exhibits a number of geomorphological and geological features indicative of a Late Weichselian ice stream, a land‐based, terminal branch of the major Baltic Ice Stream that drained the Scandinavian Ice Sheet along the Baltic Sea depression. The ice stream in the study area operated during the Young Baltic Advance. Its track on Funen is characterized by a prominent drumlin field with long, attenuated drumlins consisting of till. The field has an arcuate shape indicating ice‐flow deflection around the island's interior. Beneath the drumlin‐forming till is a major erosional surface with a boulder pavement, the stones of which have heavily faceted and striated upper surfaces. Ploughing marks are found around the boulders. Exact correspondence of striations, till fabric and drumlin orientation indicates a remarkably consistent flow direction during ice streaming. We infer that fast ice flow was facilitated by basal water pressure elevated to the vicinity of the flotation point. The ice movement was by basal sliding and bed deformation under water pressure at the flotation level or slightly below it, respectively. Subglacial channels and eskers post‐dating the drumlins mark a drainage phase that terminated the ice‐stream activity close to the deglaciation. Identification of other ice streams in the Peribaltic area is essential for better understanding the dynamics of the land‐based part of the Scandinavian Ice Sheet during the last glaciation.

The meltwater hypothesis for subglacial bedforms

This paper presents an historical and in places informal account of the meltwater hypothesis, which invokes enormous outburst floods for the formation of subglacial bedforms. It begins with a brief discussion of the difficulties of determining processes of formation for landforms, which are not seen in formation. Analogy provides a solution to these difficulties. Analogy between erosional marks at the bases of turbidites and drumlins, which were the starting point for this hypothesis, rests on the idea that inverted erosional marks at the ice bed are subsequently infilled to form drumlins. Field tests on the sedimentology, architecture, and landform associations of drumlins in the Livingstone Lake drumlin field are outlined before more extensive work on bedrock erosional forms and flood routes is introduced. Bedrock erosional forms played a central part in establishing the hypothesis since their form and ornamentation are confidently interpreted as fluvial. Their form and genesis are discussed mainly with reference to sites at French River and Wilton Creek, Ontario, though some remarkable bedrock erosional forms in Antarctica support their regional extent. Initially in the meltwater hypothesis, drumlins were thought to be cavity fills and erosional drumlins were recognized later. This development is shown to be central to the realization that drumlin composition may be inferred from drumlin form. The scale of drumlin fields, measured at about 10 3 km 2, and the magnitude of the inferred floods require that the flood events were regional. Regional-scale flood tracts in Ontario, Quebec, Alberta and the Northwest Territories extending over 1000 km in length and several hundred kilometers in width, support this suggestion. Floods, had they occurred, would have caused rapid rates of sea level rise and may have changed climate through their effects on ocean stratification and sea surface temperatures. The meltwater hypothesis covers a range of bedforms besides drumlins and bedrock erosional marks—fluting, Rogen moraine, hummocky terrain, and transverse ridges. Recent work shows how these forms are best explained by the meltwater hypothesis. The roles of water storage and release, which underpin the theory of the meltwater hypothesis, remain poorly understood.