Primary Current Lineation in the Lower Old Red Sandstone (Devonian), Anglo‐welsh Basin

Allen, J. R. L.

doi:10.1111/j.1365-3091.1964.tb00635.x

Cited by 92 publications

(36 citation statements)

References 19 publications

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“…The flat laminations of this zone represent deposition by high-velocity, upper flow regime currents. Parting lineation has been observed on bedding planes within this subdivision, supporting this interpretation (Allen, 1964).…”

Section: Subdivisions Of Dish-structured Bedssupporting

confidence: 78%

The Characteristics and Origins of Dish and Pillar Structures

Lowe¹,

LoPiccolo²

1974

SEPM JSR

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Dish structure is defined by the presence of thin, subhorizontal, flat to concaveupward, argillaceous laminations in siltstone and sandstone units. It is commonly associated with vertical or nearly vertical cross-cutting columns and sheets of massive sand termed pillars. Both form commonly in sediment ranging in grain size from coarse-grained siltstone to coarse-grained, conglomeratic sandstone. In sedimentation units greater than about 0.5 m thick, dish structure is faint and neither cuts across nor is cross-cut by other sedimentary structures. In thinner units dish structures commonly cut across primary flat laminations, climbing-ripple cross-laminations, and convolute laminations. l)ish and pillar structures form during the consolidation of rapidly deposited, underconsolidated or quick beds. During gradual compaction and dewatering, semi-permeable laminations act as partial barriers to upward-moving fluidized sediment-water slurries, forcing horizontaI flow beneath the laminations to points where continued vertical escape is possible. As water seeps upward through the confining laminations, fine sediment, planar, and low-density grains are filtered out and concentrated in the sediment pore spaces. The resulting clay-and organic-enriclaed laminations are flat dishes that may be later deformed by the upward pressure of flow around their margins and central subsidence as underlying sediment and water escape. Pillars form during forceful, explosive water escape. It is suggested that tbe shapes of dishes and pillars within an individual bed can be related to its original water content, thickness, and grain size; to the rate and magnitude of dewatering including consideration of water entering the bed from underlying consolidating sediments; and to the types and distribution of earlier-formed sedimentary structures. l)isb structures cannot be used directly to infer transport or depositional processes. \Vhere dishes are associated with or cut across primary sedimentary structures, the latter indicate deposition from currents.The study indicates that coarse-grained terrigenous sediments often have prononneed and complex consolidation histories. Many rapidly deposited beds undergo partial liquefaction mad fhfidization during consolidatiou but retain sufficient strength to resist wholesale downslope flowage in response to gravity. DISH AA'D PILLAR 5~TRUCTURES48S dishes in coarse-grained lithie sandstone. Pigeon Point Formation (Cretaceous), California. (c) Finegrained dish-structured bed showing complex and extended consolidation history; oldest dishes (1) are strongly concave, discontinuous, and have commonly been blurred by the upward flow of fluidized sediment through associated pillars; later-formed dishes (2) are flatter, more continuous, and separated vertically by sand showing well defined substructure--the dark dish lamination, an underlying zone of white claypoor sand, and an overlying zone of gray argillaceous sand. Beds showing this degree of complexity are rare and suggest more than one period of water expul...

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Section: Subdivisions Of Dish-structured Bedssupporting

confidence: 78%

The Characteristics and Origins of Dish and Pillar Structures

Lowe¹,

LoPiccolo²

1974

SEPM JSR

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show abstract

“…Experimental and field studies have demonstrated that for relatively well-sorted sand (which is generally the case for the sands in this study), the planar lamination of the deposits results of the superimposition of sediment layers of similar grain size. In this case, the mean grain orientation (marked by the long axis of the particles) is parallel to the flow direction, with two possible modes (20°and 40°) distributed symmetrically along the flow direction (Allen, 1964). When particles are settled from an overlying moving polydisperse suspension, their traction along the depositional bottom surface involves two processes, rolling and sliding, or a combination of both.…”

Section: Magnetic Fabric and Sedimentation Processesmentioning

confidence: 99%

Use of anisotropy of magnetic susceptibility (AMS) in the study of tsunami deposits: Application to the 2004 deposits on the eastern coast of Banda Aceh, North Sumatra, Indonesia

et al. 2010

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“…The succeeding divisions then find themselves in the stable field related to the distal portions of the flow, the lower division of parallel lamination being formed first and representing an upper flow regime phase. It is persuasive that it is in this division that parting lineation occurs and John Allen (1964) has recently shown that this structure is formed in the upper flow regime. The succeeding division is characterised by ripple lamination, again representing a stable bed-form, produced in the lower flow regime (Walker 1965).…”

Section: Vertical Variationmentioning

confidence: 96%