Lisbeth Louderback ESS 433 Flute/Drumlin Formation: A Review of Boulton (1976) and Shaw and Sharpe (1987) Lisbeth Louderback ESS 433

Outline Purpose of research papers Boulton (1976) Provide evidence for flute/drumlin formation and processes Boulton (1976) Flute formation Shaw and Sharpe (1987) Drumlin formation Concluding remarks and discussion

Boulton (1976) Studied modern glacially fluted surfaces in Spitsbergen, Iceland, Norway, and the Alps. Flutes originate from rigid obstructions Flutes form when till is intruded into tunnels which open up in the lee of obstacles

Boulton (1976) Here is a boulder that is transported in a glacier Slows down by ploughing into the till Which develops this wedge on its lee side The till is traced into a flute

Boulton (1976) A relationship exists between flute height and height of initiating obstruction

Boulton (1976) Further evidence for origin of glacial fluting Tunnels Patterns of strain and deformation within fluted sediments Two major fold sets Axis parallel to flow Axis transverse to flow Tunnels – reconstruct the original form of the flute (like here). The tunnel here intercepted this flute which collapsed into the tunnel Arrow shows direction of ice flow. There are two sets of folds – one with an axis parallel to ice movement indicates phase of flute formation. The second is transverse to ice movement.

Boulton (1976) Flutes are not depositional or erosional features, rather they are formed from post-depositional deformation of pre-existing materials.

Shaw and Sharpe (1987) Subglacial meltwater is responsible for both erosional and depositional drumlin formation. Small-scale features Intermediate-scale features Drumlins

Shaw and Sharpe (1987) Small-scale features Rat tails Rat tails are small ridges occurring on the lee side of an obstacle. These features are produced by water in the absence of ice Flow

Shaw and Sharpe (1987) Intermediate-scale features Flow The intermediate features are identical in form, surface texture, and their relationship to obstacles. It shows that these were also produced by subglacial meltwater. Erosional marks in limestone in Wilton Creek, southeastern Ontario Flow

Shaw and Sharpe (1987) Drumlins Drumlins in Canada. These show all the morphological characteristics of the smaller scale forms, remnant

Concluding Remarks Boulton (1976) Shaw and Sharpe (1987) Flutes (‘drumlins’) are formed by ice deformation processes Shaw and Sharpe (1987) Drumlins are formed by meltwater features

Concluding remarks Are drumlins and flutes the same feature in nature? Boulton (1976) definition of flutes: ‘long, parallel-sided ridges on deformable subglacial surfaces’ Shaw and Sharpe (1987) definition of drumlin: ‘remnant ridges resulting from erosion of the glacial substrate by sub-glacial meltwater sheets’

Discussion Source of subglacial meltwater ? Does origination of sediment (e.g. till in ice sheet environment vs. till in valley glaciers) have an effect on the formation of drumlinoid features? Coarse lags? What are other possibilities of drumlin formation? Floods generated by uplift?