The origins of s-forms: Form similarity, process analogy, and links to high-energy, subglacial meltwater flows

Shaw, John; Gilbert, Robert G.; Sharpe, D R; Lesemann, J E; Young, Robert R.

doi:10.1016/j.earscirev.2019.102994

Cited by 9 publications

(10 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…DEM identification of streamlined landforms, mega-ridges, and grooves was the basis for inferring a regional (OIS) ice stream, sourced from eastern Ontario. Previous mapping in this terrain (escarpment noses, flutings, and crescentic furrows related to turbulent flow structures) by Shaw and Gilbert (1990;Gilbert and Shaw 1992;Shaw et al 2020), their Kingston Scablands, indicates a more complex (subglacial meltwater erosion) origin for these features. Eyles and Doughty (2016) further proposed that large volumes of "limestone rubble" (Fig.…”

Section: Ice Streams In the Great Lakes Basinmentioning

confidence: 83%

“…Eyles and Doughty (2016) concluded that a Lake Ontario ice stream eroded carbonate terrain in eastern Ontario to produce glaciofluvial deposits of the ORM, without integrating detailed local mapping and sediment descriptions that support a glaciofluvial-glaciolacustine character of ORM (e.g., Barnett et al 1998;Russell and Arnott 2003;Russell et al 2004). Further, Eyles and Doughty (2016) did not consider field evidence for meltwater floods (e.g., Kingston Scablands, Gilbert 1990;Shaw and Gilbert 1990;Gilbert and Shaw 1992;Shaw et al 2020) supported by viable process models tested with flume and computational fluid dynamic experiments (e.g., Shaw 1994;Pollard et al 1996). In short, the ice-stream hypothesis needs to move beyond landform identification to process integration and understanding (Stokes 2018).…”

Section: Ice Streams In Southern Ontariomentioning

confidence: 99%

See 1 more Smart Citation

Converging ice streams: an unreasonable hypothesis for deposition of the Oak Ridges Moraine, southern Ontario

Sharpe

Russell

2020

Can. J. Earth Sci.

View full text Add to dashboard Cite

The hypothesis that Oak Ridges Moraine (ORM) formed between converging ice streams requires critical testing. Available data (e.g., digital elevation models, maps, seismic profiles, continuous cores, and pit exposures) are inconsistent with the converging ice stream hypothesis. Combined analysis of landform and subsurface data permits testing the ORM area stratigraphic sequence and sedimentary origin. Stratigraphic data indicate that drumlinized Newmarket Till, incised by north–south-oriented (tunnel) valleys, extends beneath ORM. Thus, streamlining on Newmarket Till is older than ORM and has no direct bearing on its formation. The north–south-trending valleys truncate streamlined Newmarket Till, extend to bedrock, have inset eskers, and occur beneath ORM. Hence, these valleys are older than ORM and have a subglacial rather than a proglacial origin. Overlying the mega-scale lineations and incised channels are topographically elevated (>300 m a.s.l.), ORM glaciofluvial–glaciolacustrine sequences. Its east to west paleoflow trend indicates an east–west-oriented hydraulic gradient, orthogonal to expected gradients of proposed north-south converging ice streams. The exclusive presence of ORM meltwater sediments, with rare deformation, is incompatible with a converging ice stream, deforming-bed hypothesis. Halton sediment grades upward from stratified sand (ORM) to interbedded diamicton and glaciolacustrine sediment, rather than deformation till. Halton sediment overlies ORM and consequently the proposed Halton ice streaming is younger than the moraine. Halton Till is present in few of the predicted ice stream areas, and where Halton Till is present, it has no mega-scale lineations. In sum, the weight of evidence unequivocally argues against a converging ice-stream process model for the ORM.

show abstract

Section: Ice Streams In the Great Lakes Basinmentioning

confidence: 83%

Section: Ice Streams In Southern Ontariomentioning

confidence: 99%

Converging ice streams: an unreasonable hypothesis for deposition of the Oak Ridges Moraine, southern Ontario

Sharpe

Russell

2020

Can. J. Earth Sci.

View full text Add to dashboard Cite

show abstract

“…The transverse ridges found in the southern part of the study area may also derive from water drainage along the ice/bed interface, in this case as sheet flows. Landforms including transverse features distributed on till plains and attributed to a combination of subglacial meltwater erosion and deposition have been mapped elsewhere (Glasser & Nicholson, 1998; Ojala et al, 2019, 2021; Peterson & Johnson, 2021; Shaw, 1988, 2002; Shaw et al, 2020). Alternative origins of the transverse ridges are by (1) ductile deformation of thin, soft subglacial till layer under fast‐flowing ice sheet (cf.…”

Section: Discussionmentioning

confidence: 99%

“…The impact of subglacial meltwater in the shaping of SDF is visible by various erosional features such as tunnel valleys of different sizes and shapes, kettle holes, and s‐forms that indicate energetic flows of pressurized water (cf. Kor et al, 1991; Shaw et al, 2020). These findings are consistent with numerically simulated subglacial hydrology, suggesting a surplus of meltwater at the ice/bed interface during the glacier advance over the SDF area (Hermanowski & Piotrowski, 2019).…”

Section: Study Areamentioning

confidence: 99%

Origin of glacial curvilineations by subglacial meltwater erosion: Evidence from the Stargard drumlin field, Poland

Hermanowski

Piotrowski

2022

Earth Surf Processes Landf

View full text Add to dashboard Cite

Deciphering the origin of subglacial landforms is crucial for understanding processes operating under ice sheets. Due to the inaccessibility of the ice/bed interface limiting real-time observations, the origin of these landforms is typically interpreted from the morphological and sedimentological record exposed after ice retreat, which makes the conclusions conjectural. Here, we focus on a recently discovered new type of subglacial landform called glacial curvilineations (GCLs), whose formation generates some controversy. We use LiDAR imagery and geological data to constrain the origin of GCLs found in a tunnel valley in the Stargard drumlin field, Poland. The tunnel valley is about 3800 m long, 520 m wide, and it occupies about 2 km 2 . A total of 61 individual GCLs have been mapped there; they are up to 550 m long and typically 0.5-1.5 m high, but some reach a height of up to 5 m. The GCLs are composed of mostly massive till represented by either a single or several diamicton units occasionally separated by thin layers of meltwater sand. Till macrofabrics in the GCLs and in the nearby till plain are distinctly consistent, and have high and uniform clustering strengths. At all locations, the dominant till fabric direction broadly corresponds with the ice movement direction given by the drumlin orientations, but it is oblique to the orientation of the tunnel valley and independent of the orientations of the individual GCLs. The lack of correspondence between the orientation of the GCLs and the till fabrics in them suggests that the GCLs consist of an antecedent till deposited during the drumlinizing ice advance and subsequently carved by subglacial meltwater erosion in the tunnel valley. These results substantiate the hypothesis that GCLs are erosional features postdating the material constituting them, and emphasize the role of subglacial meltwater flows as a landforming agent.

show abstract

“…2018, 2019; Shaw et al . 2020) with the consolidated high‐quality data to clarify the links between the regional unconformity and ORM sediment sequence, including the regional location of ORM.…”

Section: Methods: Study Approach and Datamentioning

confidence: 99%

Sedimentary architecture and glacial hydrodynamic significance of the stratified Oak Ridges Moraine, southern Ontario, Canada

Sharpe

Russell

2023

Boreas

View full text Add to dashboard Cite

High-quality subsurface data provide new insights into the formation of Oak Ridges Moraine (ORM), an ~80 km 3 sequence of stratified meltwater deposits resting >200 m above adjacent Lake Ontario. The ORM sedimentary succession comprises a three-part regional architecture: (i) ~north-south channel sand-gravel; (ii) channel-capping rhythmites; and (iii) east-west ridge sediments. The ORM depositional sequence overlies a regional unconformity with a cross-cutting channel network resulting from ~north-south meltwater floods that transitioned progressively (falling stage) from a ~NNE to ENE flow direction (parallels Lake Ontario depression). Seismic profiles delineate the channels and channel fill characteristics of bank-to-bank channel sedimentation of thick gradational gravel-sandmud sequences. Channel-capping mud (~100-236 rhythmites) within multiple channels beneath the ORM landform mark a widespread interval of low-energy, seasonally controlled subglacial pond deposition. During this quiescent period ice-sheet thickness adjusted to flood-induced stretching/thinning and re-profiled slopes. New ice gradients led to east-west flow and deposition of the overlying third element, a sequence of high-energy confined esker-fan sediments along ORM ridge. Close, sequential timing (~329 varve years) of channel, basin and ridge-forming architectural elements supports naming this assemblage the ORM formation. Proposed ORM floods are analogous to Icelandic j€ okulhlaups based on the size, geometry and sedimentology. The observed rhythmite interval between flood events represents a short period (~236 years) of regional meltwater storage prior to east-west ORM flooding. The ORM channel and overlying esker-fan sediment ridge represent two closely timed meltwater drainage events rather than formation by coalescing ice streams. The scale and timing of the ORM flood events are linked to rapid sea-level rise, ~13.5 ka BP. This high-resolution ORM sedimentological record may provide insights into depositional and glaciogenic controls of other large, stratified moraines. The ORM data indicate deposition in response to hydrodynamic events (outbreak floods, re-profiled ice) rather than direct climate forcing.

show abstract

The origins of s-forms: Form similarity, process analogy, and links to high-energy, subglacial meltwater flows

Cited by 9 publications

References 69 publications

Converging ice streams: an unreasonable hypothesis for deposition of the Oak Ridges Moraine, southern Ontario

Converging ice streams: an unreasonable hypothesis for deposition of the Oak Ridges Moraine, southern Ontario

Origin of glacial curvilineations by subglacial meltwater erosion: Evidence from the Stargard drumlin field, Poland

Sedimentary architecture and glacial hydrodynamic significance of the stratified Oak Ridges Moraine, southern Ontario, Canada

Contact Info

Product

Resources

About