Textural characteristics and interpretation of second-cycle, debris-flow-dominated alluvial fans (Devonian of Northern Scotland)

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Abstract

Devonian conglomerates in Northern Scotland are interpreted as a product of recycling of pre-existing, variously reworked gravels and sands and deposition in a form of alluvial fans. These second-cycle fanglomerates fringe the western margin of the Golspie Basin (marginal sector of the Orcadian Basin) and are dominated by texturally heterogeneous, structureless debris-flow conglomerates of Facies B and B1. The textural heterogeneity of Facies B, manifested through chaotically arranged bimodal and polymodal textures, highly variable amounts of matrix and unremoulded sandy blocks, indicates that the cohesive and highly competent debris flows originated through remobilisation of previously reworked, sand-enriched gravels. The debris flows of Facies B1 formed as result of resedimentation and remoulding of two, texturally and compositionally distinct, groups of sediment—angular, poorly sorted, locally derived gravels and fine-grained, well sorted, exotic sands.

The debris-flow deposits are accompanied by texturally homogeneous, massive to planar-stratified and cross-stratified conglomerates and sandstones of Facies C and C1. The latter deposits represent turbulent sheetfloods that were less competent than the debris flows and that acquired their sediment load through surficial reworking of the alluvial-fan gravels. Texturally homogeneous and structureless talus deposits of Facies A, and massive to planar-stratified sheetflood conglomerates of Facies C2 are locally derived and show first-cycle characteristics.

References (60)

  • J.B. Richardson

    Some British Lower Devonian spore assemblages and their stratigraphic significance

    Rev. Palaeobotan. Palynol.

    (1967)
  • C.B. Beaty

    Origin of alluvial fans, White Mountains, California and Nevada

    Assoc. Am. Geograph. Ann.

    (1963)
  • T.C. Blair

    Sedimentary processes, vertical stratification sequences, and geomorphology of the Roaring River alluvial fan, Rocky Mountain National Park, Colorado

    J. Sediment. Petrol.

    (1987)
  • E. Blissenbach

    Geology of alluvial fans in semiarid regions

    Bull. Geol. Soc. Am.

    (1954)
  • B.J. Bluck

    Sedimentation in some Scottish rivers of low sinuosity

    Trans. R. Soc. Edinburgh, Earth Sci.

    (1976)
  • B.J. Bluck

    Upward coarsening sedimentation units and facies lineages, Old Red Sandstone, Scotland

    Trans. R. Soc. Edinburgh, Earth Sci.

    (1986)
  • S.R. Brantley et al.

    Interrelations among pyroclastic surge, pyroclastic flow, and lahars in Smith Creek Valley during first minutes of 18 May 1980 eruption of Mount St. Helen's U.S.A.

    Bull. Volcanol.

    (1988)
  • P.E. Brown et al.

    Isotopic ages of late Caledonian granitic intrusions in the British Isles

  • M.D. Brunsden

    Mudslides

  • W.B. Bull

    The alluvial-fan environment

    Progr. Phys. Geogr.

    (1977)
  • M. Church et al.

    Paraglacial sedimentation: a consideration of fluvial processes conditioned by glaciation

    Geol. Soc. Am. Bull.

    (1972)
  • M. Church et al.

    Disequilibrium of Holocene sediment yield in glaciated British Columbia

    Nature

    (1989)
  • A.G. Collins et al.

    The age of two Old Red Sandstone sequences in southern Caithness

    Scott. J. Geol.

    (1977)
  • J.E. Costa

    Physical geomorphology of debris flows

  • M.P. Coward et al.

    Devonian basins in Northern Scotland: extension and inversion related to Late Caledonian Variscan tectonics

  • C.B. Crampton et al.

    The Geology of Caithness

    Mem. Geol. Surv.

    (1914)
  • E.C. Dapples

    Diagenesis in sandstones

  • W.M. Davis

    Sheetfloods and stream floods

    Geol. Soc. Am. Bull.

    (1938)
  • T. Dec

    Development of the Lower and Middle Old Red Sandstone sedimentary basin in eastern Sutherland, North-West Scotland

  • M. Deynoux et al.

    Late Proterozoic periglacial aeolian deposits on the West African Platform, Taoudeni Basin, western Mali

    Sedimentology

    (1989)
  • M.A. Hampton

    Competence of fine-grained debris flows

    J. Sediment. Petrol.

    (1975)
  • M.A. Hampton

    Buoyancy in debris flows

    J. Sediment. Petrol.

    (1979)
  • P.M. Harris

    Igneous and metamorphic rocks

  • P.D.W. Haughton

    Structure of some Lower Old Red Sandstone conglomerates

  • P.D.W. Haughton et al.

    Compositional variation in Lower Old Red Sandstone detrital garnets from the Midland Valley and the Anglo-Welsh Basin

    Geol. Mag.

    (1989)
  • P.D.W. Haughton et al.

    Provenance of Lower Old Red Sandstone conglomerates

  • P.L. Heller et al.

    The paradox of Lower Cretaceous gravels and initiation of thrusting in the Sevier orogenic belt, United States Western Interior

    Geol. Soc. Am. Bull.

    (1989)
  • P.L. Heller et al.

    Two-phase stratigraphic model of foreland-basin sequences

    Geology

    (1988)
  • R.LeB. Hooke

    Steady-state relations on arid-region alluvial fans in closed basins

    Am. J. Sci.

    (1968)
  • J.L. Innes

    Debris flows

    Progr. Phys. Geogr.

    (1983)

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