The sliding bed facies in esker sands and gravels: a criterion for full‐pipe (tunnel) flow?

Abstract

The Guelph esker (Ontario, Canada) consists of a sinuous, steep‐sided and segmented ridge which comprises poorly sorted, matrix‐supported sands and gravels. These sands and gravels were probably deposited during the sliding bed stage which has been observed by others in closed‐conduit hydraulic experiments. The poor sorting probably resulted from a high concentration of bed‐material load in the lower part of a subglacial tunnel, sorting being restricted to that produced by particle collisions. Inclusive graphic standard deviation is characteristically large for the sands and gravels, indicating that virtually all sizes available were in transport. The overall grain size distribution shows a characteristic undulatory shape on arithmetic probability paper, mostly because of selective removal of pebble gravel and granule sizes. This poorly sorted fades is believed to be diagnostic of transport in a subglacial tunnel flowing full of water, and may be used to identify subglacial conditions in other eskers. Deltaic sands and gravels occur downcurrent of the esker and contain a greater diversity of structures; climbing‐ripple cross‐laminae, parallel laminae and massive structure, deposited in large‐scale foresees at the end of a subglacial tunnel. These deltaic sands and gravels grade distally into outwash sands and gravels.

A Basin Analysis of the Wabigoon Area of Lake Agassiz, a Quaternary Clay Basin in Northwerstern Ontario

“…5b). Matrix-supported gravel implies contemporaneous deposition of a wide range of grain sizes and Saunderson (1977) argued that these characteristics could be produced by deposition from "...a sliding bed inside a subglacial tunnel during full-pipe flow" (p. 633). Since conduits in the Dryden area discharged below lake level, they must have been continuously filled with meltwater.…”

Role of sediment in speleogenesis; sedimentation and paragenesis

“…Debris flows are normally triggered by extreme events, such as 181 landslides, sinkhole collapse or floods. In glacial and periglacial regions, mass movements triggered 182 by solifluction and sub-glacial melt water injection, can also form diamicton deposits, possibly under 183 pipe-full 'sliding bed facies' (Saunderson, 1977). Examples of diamictons have been described from 184 caves in New Guinea (Gillieson, 1986); they are also common in caves in the UK affected by 185 periglacial processes such as Kent's Cavern, Devon (Proctor et al, 2005; Lundburg and McFarlane, 186 2007).…”

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

“…Apart from openwork esker sedimentation (e.g. Banerjee and McDonald, 1975; see R-channels in Clark and Walder (1994)), Saunderson (1977) presented the concept of sliding bed facies and full-pipe tunnel flow for the origin of esker cores. These facies are characterized by poorly sorted matrix-supported sands and gravels (Saunderson, 1977;Sutinen, 1985).…”