Skip to main content Accessibility help
×
Home

Silurian and late Ordovician K-bentonites as a record of late Caledonian volcanism in the British Isles

  • N. J. Fortey (a1), R. J. Merriman (a1) and W. D. Huff (a2)

Abstract

Silurian and late Ordovician K-bentonites of the British Isles provide a record of prolonged volcanism during the convergence of terranes associated with closure of the Iapetus and Tornquist Oceans. In the Southern Uplands–Longford-Down and Midland Valley terranes, they range from late Caradoc to Telychian, withfurther early Homerian occurrences. South of the Iapetus suture, in Eastern Avalonia, the range is Hirnantianto early Ludlow in northern England and early Telychian to earliest Ludfordian in the Welsh Borderland and English Midlands. In both cases, the distributions indicate that volcanism was more long-lived and probably more extensive than is depicted in current plate tectonic reconstructions. Average intervals between K-bentonites are estimated, based on Harland et al. (1990), as: c. 65000 years at Dob's Linn (late Aeronian to early Telychian); c. 39000 years in the Cautley area (Telychian); c. 51000 years in a borehole at Walsall (late Llandovery to Sheinwoodian). Trace element geochemistry suggests mostly subalkaline dacitic to rhyolitic magmas in which LILE-enrichment accompanies variable enrichment in crustally derived elements (Ta, Nb). The geochemistry suggests comparison with continental arc volcanism of ‘withinplate, attenuated lithosphere’ character. Ta–Nb enrichment and an absence of Eu anomalies from REE profiles are consistently present northof the Iapetus suture, but trace element patterns are less consistent south of the suture where negative Eu anomalies are generally present. Discriminant function analysis successfully distinguishes Llandovery, Wenlockand Ludlow K-bentonites from south of the Iapetus suture, and Llandovery K-bentonites from north and south ofthe suture. Those from north of the Iapetus suture probably originated in volcanism along the southern marginof Laurentia before final closure of the Iapetus Ocean. Those from south of the suture may have been derived from volcanism associated with late destruction of Iapetus and Tornquist oceanic crust, although an alternative involving volcanism at the southern margin of Eastern Avalonia or Baltica may accord better with the distribution of K-bentonites and the geographical trend of the fragmentary outcrops of Silurian volcanic rocks from southern Ireland to Belgium.

Copyright

References

Hide All
Allen, P. M., Cooper, D. C. & Fortey, N. J. 1987. Composite lava flows of Ordovician age in the English Lake District. J GEOL SOC, LONDON 144, 945–60.
Altaner, S. P., Hower, J., Whitney, G. & Aronson, J. L. 1984. Model for bentonite formation: Evidence from zoned K-bentonites in the disturbed belt, Montana. GEOLOGY 12, 412–15.
André, L., Hertogen, J. & Deutsch, S. 1986. Ordovician-Silurian magmatic provinces in Belgium and the Caledonian orogeny in middle Europe. GEOLOGY 14, 879–82.
André, L., Herbosch, A., Vanguestaine, M. & Verniers, J. 1991 Guidebook to the excursion on the stratigraphyand magmatic rocks of the Brabant massif, Belgium. ANN SOC GEOL BELGIQUE 114, 283323.
Ball, T. K. & Merriman, R. J. 1989. The petrology and geochemistry of the Ordovician Llewelyn Volcanic Group, Snowdonia, North Wales. BR GEOL SURV RES REP SG/89/1.
Bassett, M. G., Cocks, L. R. M., Holland, C. H., Rickards, R. B. & Warren, P. T. 1975. The type Wenlock series. INST GEOL SCI REP 75/13.
Batchelor, R. A. & Clarkson, E. N. K. 1993. Geochemistry of a Silurian metabentonite and associated apatite from the North Esk Inlier, Pentland Hills. SCOTT J GEOL 29, 123–30.
Batchelor, R. A. & Jeppson, L. 1994. Late Llandovery bentonites from Gotland, Sweden, as chemostratigraphic markers. GEOL J GEOL SOC, LONDON 151, 741–6.
Batchelor, R. A. & Weir, J. A. 1988. Metabentonite geochemistry: magmatic cycles and graptolite extinctions at Dob's Linn, southern Scotland. TRANS R SOC EDINBURGH: EARTH SCI 79, 1941.
Batchelor, R. A., Weir, J. A. & Spjeldnaes, N. Geochemistry of Telychian metabentonites from Vik, Ringerike District, Oslo Region. NORSK GEOL TIDSSKRIFT (in press).
Bergström, S. M., Huff, W. D, Kolata, D. R. & Kaljo, D. 1992. Silurian K-bentonites in the Iapetus region: a preliminary eventstratigraphic and tectonomagmatic assessment. GEOL FOREN STOCKHOLM FORH 114, 327–34.
Bluck, B. J. 1983. Role of the Midland Valley of Scotland in the Caledonian orogeny. TRANS R SOC EDINBURGH: EARTH SCI 74, 119–36.
Boucot, A. J., Dewey, J. F., Dineley, D. L., Fletcher, R., Fyson, W. K., Griffin, J. G., Hickox, C. F, McKerrow, W. S. & Ziegler, A. M. 1974. Geology of the Arisaig area, Antigonish County, Nova Scotia. GEOL SOC AM SPEC PAP 139, 1191.
Brusewitz, A. M. 1986. Chemical and physical properties of Palaeozoic potassium bentonites from Kinnekulle, Sweden. CLAYS CLAY MINER 34, 442–54.
Butler, A. J. 1937. On Silurian and Cambrian rocks encountered in a deep boring at Walsall, South Staffordshire. GEOL MAG 74, 240–57.
Caballero, E., Reyes, E., Delgado, A., Huertas, F. & Linares, J. 1992. The formation of bentonite: mass balance effects. APPL CLAY SCI 6, 265-76.
Cameron, T. D. J. & Anderson, T. B. 1980. Silurian metabentonites in County Down, Northern Ireland. GEOL J 15, 5975.
Cocks, L. R. M., Holland, C. H. & Rickards, R. B. 1992. A revised correlation of Silurian rocks in the British Isles. GEOL SOC, LONDON, SPEC REP 21.
Colman-Sadd, S. P., Stone, P., Swinden, H. S. & Barnes, R. P. 1992. Parallel geological development in the Dunnage Zone of Newfoundland and the Lower Palaeozoic terranes of southern Scotland: an assessment. TRANS R SOCEDINBURGH: EARTH SCI 83, 571–94.
Cope, J. C. W., Ingham, J. K. & Rawson, P. F. 1992. Atlas of palaeogeography and lithofacies. GEOL SOC, LONDON, MEM 13, 153p.
Doran, R. J. P. 1974. The Silurian rocks of the southern part of the Slieve Phelim inlier, Co. Tipperary. PROC R IRISH ACAD 74B, 193202.
Fitton, R. G. & Hughes, D. J. 1970. Volcanism and plate tectonics. EARTH PLANET SCI LETT 8, 223–28.
Fisher, R. V. & Schmincke, H.-U. 1984. Pyroclastic rocks. Berlin: Springer-Verlag.
Fordham, B. G. 1992. Chronometric calibration of mid-Ordovician to Tournasian conodontzones: a compilation from recent graphiccorrelation and isotope studies. GEOL MAG 129, 709–21.
Hagemann, F. 1966. Silurian bentonites in the Oslo region. NORGES GEOL UNDERS 242, 4661.
Harland, W. B., Armstrong, R. L., Cox, A. V., Craig, L. E., Smith, A. G. & Smith, D. G. 1990. A geologic timescale 1989. Cambridge: Cambridge University Press.
Harrison, W. B. III, 1991. Middle Silurian ash beds from the Michigan Basin. GEOL SOC AM ABSTR PROGRAMS 23, 17.
Hay, R. L., Lee, M, Kolata, D. R., Matthews, J. C. & Morton, J. P. 1988. Episodic potassic diagenesis of Ordovician tuffs in the Mississippi Valley area. GEOLOGY 16, 743–7.
Hodder, A. P. W., Green, B. E., & Lowe, D. J. 1990. A two-stage model for the formation of clay minerals from tephra-derived volcanic glass. CLAY MINER 25, 313–27.
Holland, C. H. 1969. The Irish counterpart of the Silurian of Newfoundland. AM ASSOC PET GEOL MEM 12, 298308.
Holland, C. H. 1988. The fossiliferous rocks of the Dunquin Inlier, Dingle Peninsula, County Kerry, Ireland. TRANS R SOC EDINBURGH: EARTH SCI 79, 347–60.
Howells, M. F., Reedman, A. J. & Campbell, S. D. G. 1991. Ordovician (Caradoc) marginal basin volcanism in Snowdonia (north-west Wales). London: British Geological Survey, HMSO.
Huff, W. D. & Kolata, D. R. 1989. Correlation of K-bentonite beds by chemical fingerprinting using multivariate statistics. In Cross, T. A. (ed.) Quantitative dynamicstratigraphy, 567–77, New York: Prentice Hall.
Huff, W. D. & Morgan, D. J. 1990. Stratigraphy, mineralogy and tectonic setting of Silurian K-bentonites in southern England and Wales. In Farmer, V. C. & Tardy, Y. (eds) Proceedings of the IX International Clay Conference, Strasbourg. SCI GEOL, MEM 88, 3342.
Huff, W. D., Anderson, T. B., Rundle, C. C. & Odin, G. S. 1991. Chemostratigraphy, K-Ar ages and illitizationof Silurian K-bentonites from the Central Belt of the Southern Uplands-Down-Longford terrane, British Isles. J GEOL SOC, LONDON 148, 861–8.
Hughes, R. A. 1995. The duration of Silurian graptolite zones. GEOL MAG 132, 113–5.
Hurst, J. M., Hancock, N. J. & McKerrow, W. S. 1978. Wenlock stratigraphy and palaeogeography of Wales and the Welsh Borderland. PROC GEOL ASSOC 89, 197226.
Ingham, J. K., McNamara, K. J. & Rickards, R. B. 1978. The Upper Ordovician and Silurian rocks. In Moseley, F. (ed.) The geology of the Lake District. YORKSHIRE GEOL SOC OCCAS PUBL 3, 121–45.
Jackson, A. A. 1978. Stratigraphy, sedimentology and palaeontology of the Silurian rocks of the Galty Mountain area. PROC R IRISH ACAD 78B, 91112.
King, L. M. 1992. A basin study of the Early Palaeozoic Windermere Group, Northwest England. Unpublished PhD thesis, University of Cambridge.
Kneller, B. C. 1990. The Wenlock rocks of Sheet 38 (Ambleside). British Geological Survey Onshore Geology Series, Technical Report WA/90/64.
Kneller, B. C, King, L. M. & Bell, A. M. 1993. Foreland basin development and tectonism on the northwestern margin of eastern Avalonia. GEOL MAG 130, 691–7.
Kokelaar, B. P., Howells, M. F., Bevins, R. E., Roach, R. A. & Dunkley, P. N. 1984. The Ordovician marginal basin of Wales. In Kokelaar, B. P. & Howells, M. F. (eds) Marginal basin geology: volcanic and associated sedimentary and tectonic processesin modern and ancient marginal basins. SPEC PUBL GEOL SOC, LONDON 16, 245–69.
Kolata, D. R., Frost, J. K. & Huff, W. D. 1987. Chemical correlation of K-bentonite beds in the Middle Ordovician Decorah Subgroup, upper Mississippi Valley. GEOLOGY 15, 208–11.
Koren, T. N., Abushik, A. F., Modzalevskaya, T. L. & Predtechensky, N. N. 1989. Podolia. In Holland, C. M. & Bassett, M. G. (eds), A global standard for the Silurian system. National Museum of Wales Geological Series No. 9, pp. 141–9.
Laird, M. G. & McKerrow, W. S. 1970. The Wenlock sediments of north-west Galway, Ireland. GEOL MAG 107, 297317.
Laufeld, S. & Jeppson, L. 1976. Silicification and bentonites in the Silurian of Gotland. GEOL FOREN STOCKHOLM FöRH 98, 3144.
Lawrence, D. J. D., Webb, B. C, Young, B. & White, D. E. 1986.The geoelogy of the late Ordovician and Silurian rocks (Windermere Group) in the area around Kentmere andCrook. BR GEOL SURV REP 18, No. 5, 32 pp.
Leggett, J. K., McKerrow, W. S. & Eales, M. H. 1979. The Southern Uplands: A Lower Palaeozoic accretionary prism. J GEOL SOC, LONDON 136, 755–70.
Lumsden, G. I., Tulloch, W., Howells, M. F. & Davies, A. 1967.The geology of the neighbourhood of Langholm. MEM GEOL SURV SCOTLAND.
McCaffrey, W. D., Barron, H. F., Molyneux, S. G. & Kneller, B. C. 1992. Recycled acritarchs as provenanceindicators: implications for Caledonian terrane reconstruction. GEOL MAG 129, 457–64.
McKerrow, W. S., Dewey, J. S. & Scotese, C. R. 1991. The Ordovician and Silurian development of the lapetus Ocean. In Bassett, M. G., Lane, P. D. & Edwards, D. (eds) The Murchison Symposium: Proceedings of an international conference on the Silurian System. SPEC PAP PALAEONTOL 44, 165–78.
Merriman, R. J. & Roberts, B. 1990. Metabentonites in the Moffat Shale Group, Southern Uplands of Scotland: geochemical evidence of ensialic marginal basin volcanism. GEOL MAG 127, 259–71.
Merriman, R. J., Rex, D. C, Soper, N. J. & Peacor, D. R. 1995.The age of Acadian cleavage in northern England, UK: K-Ar and TEM analysis of a Silurian metabentonite. PROC YORKSHIRE GEOL SOC 50, 255–65.
Millward, D., Moseley, F. & Soper, N. J. 1978. The Eycott and Borrowdale volcanic rocks. In Moseley, F. (ed.), YORKSHIRE GEOL SOC OCCAS PUBL 3, 91120.
Milodowski, A. E. & Zalasiewicz, J. A. 1991. Redistribution of rare earth elements during diagenesis of turbidite/hemipelagite mudrock sequences of Llandovery age from central Wales. In Morton, A. C, Todd, S. P. & Haughton, P. D. (eds) Developments in sedimentary provenance studies. GEOL SOC SPEC PUBL 57, p1011124.
Mole, M. J., Trewin, N. H. & Still, J. 1992. Mobility of the high field strength, rare earth elements andyttrium during late diagenesis. J GEOL SOC, LONDON 149, 689–92.
Morris, J. H. 1987. The Northern Belt of the Longford-Down Inlier, Ireland and Southern Uplands: an Ordovician back-arc basin. J GEOL SOC, LONDON 144, 773–86.
Mossier, J. H. & Hayes, J. B. 1966. Ordovician potassium bentonites of Iowa. J SEDIMENT PETROL 36, 414427.
Murphy, F. C. et al. 1991. An appraisal of Caledonian suspect terranes inIreland. IRISH J EARTH SCI 11, 1141.
Parkin, J. 1976. Silurian rocks of the Bull's Head, Annascaul and Derrymore glen inliers, Co. Kerry. PROC R IRISH ACAD 76B, 577606.
Pearce, J. A., Harris, N. B. W. & Tindle, A. G. 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. J PETROL 25, 956–83.
Pearce, R. B. 1995. The geochemistry of Llandovery and Wenlock age K-bentonites in theSouthern Uplands. SCOTT J GEOL 31,23–8.
Pharaoh, T. C, Merriman, R. J., Evans, J. A., Brewer, T. S., Webb, P. C. & Smith, N. J. P. 1991. Early Palaeozoic arc-related volcanism in the concealed Caledonides of southern Britain. ANN SOC GEOL BELGIQUE 114, 6391.
Pharaoh, T. C, Brewer, T. S. & Webb, P. C. 1993. Subduction-related magmatism of late Ordovician age in Eastern England. GEOL MAG 130, 647–56.
Phillips, W. E. A. 1974. The stratigraphy, sedimentary environments and palaeogeography of the Silurian strata of Clare Island, Co, Mayo. J GEOL SOC, LONDON 130, 1941.
Phipps, C. B. & Reeve, F. A. E. 1967. Stratigraphy and geological history of the Malvern, Abberley and Ledbury hills. GEOL J 5, 339–68.
Pickering, K. T., Bassett, M. G. & Siveter, D. J. 1988. Late-Ordovician early-Silurian destruction of thelapetus Ocean: Newfoundland, British Isles and Scandinavia—a discussion. TRANS R SOC EDINBURGH: EARTH SCI 79,361–82.
Piper, D. J. W. 1972. Sedimentary environments and palaeogeography of the late Llandovery and earliest Wenlock of North Connemara, Ireland. J GEOL SOC, LONDON 128, 3351.
Piper, D. J. W. 1975. A reconnaissance of the sedimentology of the lower Silurian mudstones, English Lake District. SEDIMENTOLOGY 22, 623–30.
Rickards, R. B. 1967. The Wenlock and Ludlow succession in the Howgill Fells (north-west Yorkshire and Westmorland). Q J GEOL SOC, LONDON 123, 215–49.
Rickards, R. B. 1970. The Llandovery (Silurian) graptolites of the Howgill Fells, northern England. PALAEONTOL SOC MONOGR 123 (for 1969), 1108.
Rickards, R. B. 1978. Silurian. In Moseley, F.(ed.) Geology of the Lake District. YORKSHIRE GEOL SOC OCCAS PUBL 3, 130–45.
Roberts, B. & Merriman, R. J. 1990. Cambrian and Ordovician metabentonitesand their relevance to the origins of associated mudrocks in the northern sector of the Lower Palaeozoic Welsh marginal basin. GEOL MAG 127, 3143.
Romano, M. & Spears, D. A. 1991. Bentonites from the Horton Formation (Upper Silurian) of Ribblesdale, Yorkshire. PROC YORKSHIRE GEOL SOC 48, 277–85.
Sanderson, R. W. & Cave, R. 1980. Silurian volcanism in the central Welsh Borderland. GEOL MAG 117, 455–62.
Scotese, C. R. & McKerrow, W. S. 1990. Revised world maps and introduction. In McKerrow, W. S. & Scotese, C. S. (eds) Palaeozoic palaeogeography and biogeography. MEM GEOL SOC, LONDON 12, 124.
Scott, R. W. & Kneller, B. C. 1990. A report on the Ashgill and Llandoveryage rocks of Sheet 38 (Ambleside). British Geological Survey Onshore Geology Series, Technical Report WA/90/63, 35 p.
Self, S. & Sparks, R. S. J. (eds) 1981. Tephra studies. Proceedings of the NATO Advanced Studies Institute ‘Tephra Studies as a Tool in Quaternary Research’.Dordrecht, Boston, London: D. Reidel Publishing Co.
Sloan, R. J. & Bennett, M. C. 1990. Geochemical character of Silurian volcanism in SW Ireland. J GEOL SOC, LONDON 147,1051–60.
Smith, D. G. W. 1967. The petrology and mineralogy of some Lower Devonian bentonites from Gaspe, P. Q. CAN MINERAL 9, 141165.
Smith, R. A., Johnston, T. P. & Legg, I. C. 1991. Geology of the country around Newtownards. London, HMSO: British Geological Survey.
Soper, N. J. 1994. The Lower Palaeozoic rocks of 1:10000 sheets SD28SW, SD28SE, SD27NW andSD27NE, Low Furness, Cumbria. BR GEOL SURV TECH REP WA/94/61, 26 p.
Soper, N. J. & Hutton, D. H. W. 1984. Late Caledonian displacements in Britain: implications for a three-plate collision model. TECTONICS 3, 781–94.
Soper, N. J. & Woodcock, N. H. 1990. Silurian collision and sediment dispersal patterns in southern Britain. GEOL MAG 127, 527–42.
Soper, N. J., Webb, B. C. & Woodcock, N. H. 1987. Late Caledonian (Acadian) transpression in north-west England: timing, geometry and geotectonic significance. PROC YORKSHIRE GEOL SOC 46, 175–92.
Spjeldnaes, N. 1959. Silurian bentonites from Gotland, Sweden. GEOL FOREN STOCKHOLM FORH 8, 582–7.
Stone, P., Floyd, J. D., Barnes, R. P. & Lintern, B. C. 1987. A sequential back-arc and foreland basin thrust duplex model for the Southern Uplands of Scotland. J GEOL SOC, LONDON 144, 753–64.
Styles, M. T., Stone, P. & Floyd, J. D. 1989. Arc detritus in the Southern Uplands: mineralogical characterisation of a ‘missing’ terrane. J GEOL SOC, LONDON 146, 397400.
Teale, C. T. & Spears, D. A. 1986. The mineralogy and origin of some Silurian bentonites, Welsh Borderland, UK. SEDIMENTOL 33, 757–65.
Thirlwall, M. F. 1988. Geochronology of Late Caledonian magmatism in northern Britain. J GEOL SOC, LONDON 145, 951–67.
Thorpe, R. S., Leat, P. T., Bevins, R. E. & Hughes, D. J. 1989. Lateorogenic alkaline/subalkaline Silurian volcanism of the Skomer Volcanic Group in the Caledonides of South Wales. J GEOL SOC, LONDON 146, 125–32.
Tipper, J. C. 1976. The stratigraphy of the North Esk Inlier, Midlothian. SCOTT J GEOL 12, 1522.
Tucker, R. D., Krogh, T. E., Ross, R. J. Jr & Williams, S. M. 1990. Time-scale calibration by high-precision U-Pb zircon dating of interstratified volcanic ashes in the Ordovician and Lower Silurian stratotypes of Britain. EARTH PLANET SCI LETT 100, 51–8.
Turner, J. S. 1935. Gothlandian vulcanicity in Western Europe. GEOL MAG 72, 145–51.
Van Der Kamp, P. C. 1969. The Silurian volcanic rocks of the Mendip Hills, Somerset, and the Tortworth area, Gloucestershire, England. GEOL MAG 106, 542–53.
Walker, G. P. L. 1981. Plinian eruptions and their products. BULL VOLCANOL 44, 223–40.
Walton, E. K. & Oliver, G. J. H. 1991. Lower Palaeozoic—structure and palaeogeography. In Craig, G. Y. (ed.) Geology of Scotland (Third edition). London: The Geological Society. 612 pp.
White, D. E. & Lawson, J. D. 1978. The stratigraphy of new sections in theLudlow Series of the type area, Ludlow, Salop, England. INST GEOL SCI REP 78/30.
Williams, D. M., O'Connor, P. D. & Menuge, J. 1992. Silurian turbidite provenance and the closure ofIapetus. J GEOL SOC, LONDON 149, 349–57.
Wilson, D. W. R. 1954. The stratigraphy and palaeontology of the Valentian rocks of Cautley (Yorks W.R.). Unpublished PhD thesis, University of Birmingham.
Winchester, J. A. & Floyd, P. A. 1977. Geochemical discrimination of different magma series and their differentiation products using immobile elements. CHEM GEOL 20, 325–43.
Woodcock, N. H. & Pharaoh, T. C. 1993. Silurian facies beneath East Anglia. GEOL MAG 130, 681–90.
Wright, A. D. 1985. The Ordovician-Silurian boundary at Keisley, northern England. GEOL MAG 122, 261–73.
Zeigler, A. M., McKerrow, W. S., Burne, R. V. & Baker, P. E. 1969. Correlation and environmental setting of the Skomer Volcanic Group, Pembrokeshire. PROC GEOLASSOC 80, 409-40.
Zhang, Y.-S. & Huff, W. D. 1994. Grain size characteristics of a Middle Ordovician eruption and its source area. In Lanphere, M. A., Dalrymple, G. B. & Turrin, B. D. (eds), Abstracts of the Eighth International Conference on Geochronology, Cosmochronology and Isotope Geology. US GEOL SURV CIRC 1107, 364.

Keywords

Silurian and late Ordovician K-bentonites as a record of late Caledonian volcanism in the British Isles

  • N. J. Fortey (a1), R. J. Merriman (a1) and W. D. Huff (a2)

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