Skip to main content Accessibility help
×
Home

Sedimentation and tectonism in the Middle Ordovician of the Girvan district, SW Scotland

  • David Ince (a1)

Abstract

The Kirkland Conglomerate and the Benan Conglomerate and associated sediments of the Barr Group (Ordovician—Llanvirn-Llandeilo) of the Girvan district, SW Scotland record the development of two fan-delta systems situated on the northern margin of Iapetus. The intervening Stinchar Limestone represents a shallow marine fan-delta abandonment facies. Subaerial fan-delta deposits are seen at the lowest exposed horizons within the Kirkland Conglomerate. Transgression and eventual abandonment of the fan-delta system is recorded by (1) matrix-rich gravels forming the topmost horizons of the unit. (2) subaqueous distributary channel sands of the overlying transitional sandstone and associated shallow-marine carbonates of the Auchensoul Limestone and (3) shallow-marine sandstones of the Confinis Flags. Following a period of shallow-water sedimentation (Stinchar Limestone), a phase of rapid subsidence occurred during the upper Llandeilo, broadly synchronous with the Nemagraptus gracilis Zone transgression. Lowermost horizons of the succeeding Benan Conglomerate comprise re-sedimented gravels and laterally equivalent ‘outer shelf’ deposits (Superstes Mudstone). Renewal of coarse clastic sedimentation resulted from source area uplift related to granite plutonism, responsible also for the rapid subsidence of basinal areas. Fan-delta progradation is recorded by the occurrence of braided-fluvial deposits and shallow-marine carbonates at higher stratigraphical levels within the unit. Progradation of the fan-delta complex resulted from a gradual reduction in subsidence rates along basin-margin faults.

Fan-deltas of the Barr Group prograded southwards, from a SW—NE-trending faultdelineated basin margin, across a narrow shelf area. To the S of the shelf area defined by Barr Group outcrop, sediments of the Tappins complex accumulated in outer shelf, ?slope and base of slope settings.

The thickness of individual conglomerate units (>150 m—Kirkland Conglomerate, and up to 700 m—Benan Conglomerate), the associated high sedimentation rates, narrowness of the shelf area, and distribution and style of basin-margin faults indicate that oblique-slip motion along the northern margin of Iapetus may have provided a major control over Middle Ordovician sedimentation in the Girvan district.

Copyright

References

Hide All
Aftalion, M., van Breeman, D. & Bowes, D. R. 1984. Age constraints on basement of the Midland Valley of Scotland. TRANS R SOC EDINBURGH SCI 75, 5364.
Anderton, R., Bridges, P., Leeder, M. & Sellwood, B. 1979. A dynamic stratigraphy of the British Isles. London: George Allen & Unwin.
Barret, T. J., Jenkyns, H. C., Leggett, J. K. & Robertson, A. H. F. 1982. Comment: Age and origin of Ballantrae Ophiolite and its significance to the Caledonian orogeny and Ordovician time scale GEOLOGY 10, 331.
Blissenbach, E. 1954. Geology of alluvial fans in arid regions. BULL GEOL SOC AM 65, 175–90.
Bluck, B. J. 1969. Old Red Sandstone and other Palaeozoic conglomerates of Scotland. In Kay, M. (ed.) North Atlantic geology and continental drift—a symposium, 711–23. MEM AM ASSOC PETROL GEOL 12.
Bluck, B. J. 1984. Pre-Carboniferous history of the Midland Valley of Scotland. TRANS R SOC EDINBURGH EARTH SCI 75, 275–95.
Boothroyd, J. C. & Ashley, G. M. 1975. Process, bar morphology and sedimentary structures on braided outwash fans, northeastern Gulf of Alaska. In Jopling, A. V. & McDonald, B. C. (eds) Glaciofluvial and glacio-lacustrine sedimentation, 193222. SOC ECON PALAEONTOL MINERAL SPEC PUBL 23.
Boothroyd, J. C. & Nummedal, D. 1978. Proglacial braided outwash: a model for humid alluvial fan deposits. In Miall, A. D. (ed.) Fluvial Sedimentology, 641–68. MEM CAN SOC PETROL GEOL 5.
Church, W. R. & Gayer, R. A. 1973. The Ballantrae ophiolite. GEOL MAG 110, 497510.
Clifton, H. E. 1973. Pebble segregation and bed lenticularity in wave worked versus alluvial gravel. SEDIMENTOLOGY 26, 173–87.
Daily, B., Moore, P. S. & Rust, B. R. 1980. Terrestrial-marine transition in the Cambrian rocks of Kangaroo Island, South Australia. SEDIMENTOLOGY 27, 379–99.
Davies, I. C. & Walker, R. G. 1974. Transport and deposition of resedimented conglomerates: the Cap Enrage Formation, Cambro-Ordovician, Gaspe, Quebec. J SEDIMENT PETROL 44, 1200–16.
Dewey, J. F. 1971. A model for the Lower Palaeozoic evolution of the Southern margin of the Early Caledonides of Scotland and Ireland. SCOTT J GEOL 7, 219–40.
Dewey, J. F. 1982. Plate tectonics and the evolution of the British Isles. J GEOL SOC LONDON 139, 371412.
Dobkins, J. E. & Folk, R. L. 1970. Shape development on Tahiti-Nui. J SEDIMENT PETROL 40, 1167–203.
Fortey, R. A. 1975. Early Ordovician trilobite communities. FOSSILS STRATA 4, 339–60.
Graham, A. M. and Upton, B. G. J. 1978. Gneisses in diatremes, Scottish Midland Valley: petrology and tectonic implications. J GEOL SOC LONDON 135, 219–28.
Gvirtzman, G. and Buchbinder, B. 1978. Recent and Pleistocene coral reefs and coastal sediments of the Gulf of Elat. INT CONGR SEDIMENT Jerusalem, 1978, 161–91.
Hayward, A. B. 1982. Tertiary ophiolite related sedimentation in S.W. Turkey. Unpublished Ph.D. Thesis, Edinburgh University.
Hempton, M. R., Dunn, L. A. and Dewey, J. F. 1983. Sedimentation in an active strike-slip basin, Southeastern Turkey. J GEOL 91, 401–12.
Holland, C. H., Audley-Charles, M. G., Bassett, M. G., Cowie, J. W., Curry, D., Fitch, F. J., Hancock, J. M., House, M. R., Ingham, J. K., Kent, P. E., Morton, N., Ramsbottom, W. H. C., Rawson, P. F., Smith, D. B., Stubblefield, C. J., Torrens, H. S., Wallace, P. & Woodland, A. W. 1978. A guide to stratigraphical procedure. SPEC REP GEOL SOC LONDON 10.
Ince, D. M. 1983. Shallow-water facies and environments in the Middle Ordovician of the Girvan area, Strathclyde. Unpublished Ph.D Thesis, Edinburgh University.
Ingham, J. K. 1978. Geology of a continental margin, 2: middle and late Ordovician transgression, Girvan. In Bowes, D. R. & Leake, B. E. (eds) Crustal evolution in northwestern Britain and adjacent areas, 163176. GEOL J SPEC ISSUE 10.
Karig, D. E. 1982. Initiation of subduction zones: implications for arc evolution and ophiolite development. In Leggett, J. K. (ed.) Trench-Forearc Geology: Sedimentation and Tectonism on Modern and Active Plate Margins, 563–76. SPEC PUBL GEOL SOC LONDON 10.
Kelling, G. 1962. The petrology and sedimentation of the Upper Ordovician rocks of the Rhinns of Galloway, southwest Scotland. TRANS R SOC EDINBURGH 65, 107–37.
Keunen, P. H. 1953. Graded bedding with observations on the Lower Palaeozoic rocks of Britain. VERH K NED AKAD WET AFD NAT 20, 117.
Lambert, R. St J., Holland, J. G. & Leggett, J. K. 1981. Petrology and tectonic setting of some Ordovician volcanic rocks from the Southern Uplands of Scotland. J GEOL SOC LONDON 138, 421–36.
Lamont, A. & Lindstrom, M. 1957. Arenigian and Llandelian cherts identified in the Southern Uplands by means of conodonts, etc. TRANS EDINBURGH GEOL SOC 17, 6070.
Lapworth, C. 1882. The Girvan Succession. Q J GEOL SOC LONDON 38, 537666.
Leggett, J. K. 1980. The sedimentological evolution of a Lower Palaeozoic accretionary fore-arc in the Southern Uplands of Scotland, SEDIMENTOLOGY 27, 401–17.
Leggett, J. K., McKerrow, W. S. & Casey, D. N. 1982. The anatomy of a Lower Palaeozoic accretionary fore-arc: the Southern Uplands of Scotland. In Leggett, J. K. (ed.) Trench-Forearc Geology: Sedimentation and Tectonics on Modern Active Plate Margins, 495520. GEOL SOC LONDON SPEC PUBL 10.
Leggett, J. K., McKerrow, W. S. & Eales, M. H. 1979. The Southern Uplands of Scotland: a Lower Palaeozoic accretionary prism. J GEOL SOC LONDON 136, 755–70.
Leggett, J. K., McKerrow, W. S. & Soper, N. J. 1983. A model for the crustal evolution of Southern Scotland. TECTONICS 2, 187210.
Longman, C. D., Bluck, B. J. & van Breemen, O. 1979. Ordovician conglomerates and the evolution of the Midland Valley. NATURE 280, 578–81.
McKerrow, W. S., Leggett, J. K. & Eales, M. H. 1977. Imbricate thrust model of the Southern Uplands of Scotland. NATURE 267, 237–39.
Miall, A. D. 1977. A review of the braided-river depositional environment. EARTH SCI REV 13, 162.
Nemec, W., Porebski, S. J. & Steel, R. J. 1980. Texture and structure of resedimented conglomerates: examples from the Ksiaz Formation (Fammenian-Tournaisian) Southwestern Poland. SEDIMENTOLOGY 27, 519–38.
Peach, B. N. and Horne, J. 1899. The Silurian rocks of Britain. MEM GEOL SURV U K 1.
Phillips, W. E. A., Stillman, C. J. & Murphy, T. 1976. A Caledonian plate tectonic model. J GEOL SOC LONDON 132, 579609.
Piper, D. J. W. 1972. Trench sedimentation in the Lower Palaeozoic of the Southern Uplands. SCOTT J GEOL 8, 289–91.
Reading, H. G. 1982. Sedimentary basins and global tectonics. PROC GEOL ASSOC 93, 321–50.
Ross, R. J. & Ingham, J. K. 1970. Distribution of the Toquima-Table Head (Middle Ordovician Whiterock) faunal realm in the Northern Hemisphere. BULL GEOL SOC AM 81, 393408.
Rust, B. R. 1972. Pebble orientation in fluvial sediments. J SEDIMENT PETROL 42, 384–88.
Scott, K. M. & Gravlee, G. C. 1968. Flood surge of the Rubicon River, California—hydrology, hydraulics and boulder transport. PROF PAP U S GEOL SURV 422–M.
Sneed, F. D. & Folk, R. L. 1958. Pebbles in the Lower Colorado River, Texas—a study in particle morphogenesis. J GEOL 66, 114–50.
Surlyk, F. 1978. Submarine fan sedimentation along fault scarps on tilted fault blocks. (Jurassic-Cretaceous boundary, East Greenland.) GRONLANDS GEOL UNDERS BULL 128.
Tripp, R. P. 1976. Trilobites from the basal Superstes mudstones (Ordovician) at Aidons Quarry, near Girvan Ayrshire. TRANS R SOC EDINBURGH 69, 369423.
Upton, B. G. J., Aspen, P. & Hunter, R. H. 1984. Xenoliths and their implications for the deep geology of the Midland Valley of Scotland and adjacent regions. TRANS R SOC EDINBURGH EARTH SCI 75, 6570.
Vail, P. R., Mitchum, R. M. & Thompson, S. 1977. Global cycles of relative changes in sea level. In Payton, C. E. (ed.) Seismic Stratigraphy—applications to hydrocarbon exploration, 8397. AM ASSOC PET GEOL MEM 26.
Vos, R. G. 1981. Sedimentology of an Ordovician fan delta complex, Western Libya. SEDIM GEOL 29, 153–70.
Walker, R. G. 1978. Turbidites and associated coarse clastic deposits. In Walker, R. G. (ed.) Fades Models, 91103. GEOSCI CAN REPR SER 1.
Walton, E. K. 1965. The Lower Palaeozoic Rocks. In Craig, G. Y. (ed.) The Geology of Scotland, 161229. Edinburgh: Oliver & Boyd.
Wescott, W. A. and Ethridge, F. G. 1980. Fan-delta sedimentology and tectonic setting—Yallahs Fan Delta, southeast Jamaica. BULL AM ASSOC PET GEOL 64, 374–99.
Wescott, W. A. & Ethridge, F. G. 1983. Eocene fan delta-submarine fan deposition in the Wagwater Trough, east-central Jamaica. SEDIMENTOLOGY 30, 235–47.
Williams, A. 1959. A structural history of the Girvan district, southwest Ayrshire. TRANS R SOC EDINBURGH 63, 629–67.
Williams, A. 1962. The Barr and Lower Ardmillan series (Caradoc) of the Girvan district, southwest Ayrshire, with descriptions of the Brachiopoda. MEM GEOL SOC LONDON 3.
Yardley, B. W. D., Vine, F. J. & Baldwin, C. T. 1982. The plate tectonic setting of NW Britain and Ireland in late Cambrian and early Ordovician times. J GEOL SOC LONDON 139, 455–63.

Keywords

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed