Hostname: page-component-78c5997874-dh8gc Total loading time: 0 Render date: 2024-11-08T05:09:57.016Z Has data issue: false hasContentIssue false
  • English
  • Français

Metabentonite geochemistry: magmatic cycles and graptolite extinctions at Dob's Linn, southern Scotland

Published online by Cambridge University Press:  03 November 2011

R. A. Batchelor  and
J. A. Weir
R. A. Batchelor
Affiliation:
R. A. Batchelor and J. A. Weir, Department of Geography and Geology, University of St Andrews, St Andrews, Fife KY16 9ST, Scotland, U.K.
J. A. Weir
Affiliation:
R. A. Batchelor and J. A. Weir, Department of Geography and Geology, University of St Andrews, St Andrews, Fife KY16 9ST, Scotland, U.K.
Get access Rights & Permissions [Opens in a new window]

Abstract

The Moffat Shale Group is a condensed, variable and partly pelagic sequence of mudrocks of Llandeilo—Llandovery age. The sequence has a five-fold lithological subdivision based mainly on the occurrence of grey mudstones within a succession otherwise dominated by fully euxinic black graptolitic mudrocks. Associated with the black mudrocks, especially in the Llandovery, are metabentonite beds which achieve a climax, both in thickness and in number, within the top quarter of the mudrock sequence. A geochemical and mineralogical study has confirmed a volcanic origin for the metabentonites. Major element data highlight a carbonate-dominated environment above the gregarius—convolutus Zones boundary. Phosphorus levels reach a peak at the same boundary, as well as at the Caradoc—Ashgill boundary where phosphorite horizons are known from Wales and Norway. Immobile trace elements have highlighted regular changes in source magma composition. Prolonged periods of crystal fractionation in magmas of intermediate composition gave rise, on eruption, to large volumes of silicic ash which had a deleterious effect on graptolite species and led to local extinctions. Regular fluctuations in ash composition from silicic to intermediate are ascribed to alternating fractionation and magma mixing cycles.

Keywords

Moffat Shale GroupmudrockspetrogenesisSouthern Uplandsvolcanic ash
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 79 , Issue 1 , 1988 , pp. 19 - 41
Copyright
Copyright © Royal Society of Edinburgh 1988

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Anderson, T. B., & Oliver, G. J. H. 1986. The Orlock Bridge Fault: a major late Caledonian sinistral fault in the Southern Uplands terrane, British Isles, TRANS R SOC EDINBURGH EARTH SCI 77, 203–22.CrossRefGoogle Scholar
Bailey, J. C. 1981. Geochemical criteria for a refined tectonic discrimination of orogenic andesites. CHEM GEOL 32, 139–54.CrossRefGoogle Scholar
Berry, W. B. N. 1987. The Ordovician-Silurian boundary: new data, new concerns. LETHAIA 20, 209–16.Google Scholar
Berry, W. B. N. & Boucot, A. J. 1973. Glacio-eustatic control of Late Ordovician—Early Silurian platform sedimentation and faunal changes. BULL GEOL SOC AM 84, 275–84.2.0.CO;2>CrossRefGoogle Scholar
Berry, W. B. N., Orth, C. J., Wilde, P., Hunt, M. Q. & Gilmore, J. S. 1984. Chemostratigraphy at Dob's Linn, Scotland. ABSTR WITH PROG 52856. GEOL SOC AM ABSTR 16 (6), 444.Google Scholar
Boeuf, S. & Biju-Deval, B. 1966. Ampleur des glaciations ‘siluriens’ du Sahara. REV INST FR PETR 21, 363–81.Google Scholar
Brenchley, P. J. & Cullen, B. 1984. The environmental distribution of associations belonging to the Hirnantia fauna—evidence from North Wales and Norway. In Bruton, D. L. (ed.) Aspects of the Ordovician System, 113–26. PALAEONT CONTRIB UNIV OSLO 295. Oslo: Universitetsforlaget.Google Scholar
Brenchley, P. J. & Newall, G. 1984. Late Ordovician environmental changes and their effect on faunas. In Bruton, D. L. (ed.) Aspects of the Ordovician System, 65–80. PALAEONT CONTRIB UNIV OSLO 295. Oslo: Universitetesforlaget.Google Scholar
Cameron, T. D. J. & Anderson, T. B. 1980. Silurian metabentonites in County Down, Northern Ireland. GEOL J 15, 59–75.CrossRefGoogle Scholar
Cave, R. 1965. The Nod Glas sediments of Caradoc age in North Wales. GEOL J 4, 279–98.CrossRefGoogle Scholar
Xu, Chen 1984. Influence of the Late Ordovician glaciation on basic configuration of the Yangtze Platform in China. LETHAIA 17, 51–60.CrossRefGoogle Scholar
Cocks, L. R. M. & Price, D. 1975. The biostratigraphy of the upper Ordovician and lower Silurian of south-west Dyfed, with comments on the Hirnantia fauna. PALAEONTOLOGY 18, 703–24.Google Scholar
Dangeard, L. & Dore, F. 1971. Facies glaciales de l'Ordovicien supérieur en Normandie. In Colloque Ordovicien-Silurien, Brest 1971, 119–27. MEM BUR RECH GEOL MIN 73.Google Scholar
Destombes, J. 1968. Sur la présence d'une discordence générate de ravinement d'âge Ashgill supérieur dans l'Ordovicien terminal de l'Anti-Atlas (Maroc). C R ACAD SCI FR 267, 565–7.Google Scholar
Dow, D. B., Beyth, M. & Hailu, T. 1971. Palaeozoic glacial rocks recently discovered in northern Ethiopia. GEOL MAG 108, 53–9.CrossRefGoogle Scholar
Fairbridge, R. W. 1971. Upper Ordovician glaciation in northwest Africa?: Reply. BULL GEOL SOC AM 82, 269–74.CrossRefGoogle Scholar
Fischer, R. V. & Schminke, H. U. 1984. Pyroclastic Rocks. Berlin: Springer-Verlag.CrossRefGoogle Scholar
Fortey, R. A. 1984. Global earlier Ordovician transgressions and regressions and their biological implications. In Bruton, D. L. (ed.) Aspects of the Ordovician System, 37–50. PALAEONT CONTRIB UNIV OSLO 295. Oslo: Universitetsforlaget.Google Scholar
Furnes, H., Brekke, K., Nordås, J. & Hertogen, J. 1986. Lower Palaeozoic convergent plate margin volcanism on Båmlo, southwest Norwegian Caledonides: geochemistry and petrogenesis. GEOL MAG 123, 123–42.CrossRefGoogle Scholar
Gill, J. B. 1981. Orogenic Andesites and Plate Tectonics. Berlin: Springer-Verlag.CrossRefGoogle Scholar
Holm, P. E. 1985. The geochemical fingerprints of different tectonomagmatic environments using hygromagmatophile element abundances of tholeiitic basalts and basaltic andesites. CHEM GEOL 51, 303–23.CrossRefGoogle Scholar
Hower, J. & Mowatt, T. C. 1966. The mineralogy of illites and mixed-layer montmorillonite. AM MINERAL 51, 825–54.Google Scholar
Huppert, H. E., Sparks, R. S. J. & Turner, J. S. 1982. Effects of volatiles on mixing in calc-alkaline magma systems. NATURE 297, 554–7.CrossRefGoogle Scholar
Ingham, J. K. & Wright, A. D. 1970. A revised classification of the Ashgill Series. LETHAIA 3, 233–42.CrossRefGoogle Scholar
Izett, G. A. 1981. Volcanic ash beds: recorders of Upper Cenozoic silicic pyroclastic volcanism in the western United States, J GEOPHYS RES 86, 10200–22.CrossRefGoogle Scholar
Johnson, M. E., Cocks, L. R. M. & Copper, P. 1981. Late Ordovician—Early Silurian fluctuations in sea level from eastern Anticosti Island, Quebec. LETHAIA 14, 73–82.CrossRefGoogle Scholar
Langmuir, C. H., Vocke, R. D. Jr., Hanson, G. N. & Hart, S. R. 1978. A general mixing equation with applications to Icelandic basalts. EARTH PLANET SCI LETT 37, 380–92.CrossRefGoogle Scholar
Lapworth, C. 1878. The Moffat Series. Q J GEOL SOC LONDON 34, 240–346.CrossRefGoogle Scholar
Leggett, J. K. 1978. Eustacy and pelagic regimes in the Iapetus Ocean during the Ordovician and Silurian. EARTH PLANET SCI LETT 41, 163–9.CrossRefGoogle Scholar
Leggett, J. K., McKerrow, W. S., Cocks, L. R. M. & Rickards, R. B. 1981. Periodicity in the early Palaeozoic marine realm. J GEOL SOC LONDON 138, 167–76.CrossRefGoogle Scholar
Lenz, A. C. 1976. Late Ordovician-Early Silurian glaciation and the Ordovician-Silurian boundary in the northern Canadian Cordillera. GEOLOGY 4, 313–7.2.0.CO;2>CrossRefGoogle Scholar
Le Roex, A. P. 1985. Geochemistry, mineralogy and magmatic evolution of the basaltic and trachytic lavas of Gough Island, South Atlantic. J PETROL 26, 149–86.CrossRefGoogle Scholar
Lespérance, P. J. 1974. Hirnantian faunas of the Percé area (Quebec) and the Ordovician-Silurian boundary. AM J SCI 274, 10–30.CrossRefGoogle Scholar
Lespérance, P. J., Barnes, C. R., Berry, W. B. N., Boucot, A. J. & En-zhi, Mu 1987. The Ordovician-Silurian boundary stratotype: Consequences of its approval by the IUGS. LETHAIA 20, 217–22.Google Scholar
Lindsay, J. F. 1970. Depositional environment of Palaeozoic glacial rocks in the central Transantarctic Mountains. BULL GEOL SOC AM 81, 1149–72.CrossRefGoogle Scholar
McClure, H. A. 1978. Early Palaeozoic glaciation in Arabia. PALEOGEOGR PALAEOCLIMATOL PALAEOECOL 25, 315–26.CrossRefGoogle Scholar
Morris, J. H. 1987. The Northern Belt of the Longford—Down Inlier, Ireland and Southern Uplands, Scotland: an Ordovician back-arc basin. J GEOL SOC LONDON 144, 773–86.CrossRefGoogle Scholar
Nilsson, R. 1960. A preliminary report on a boring through Middle Ordovician Strata in Western Scania (Sweden). GEOL FÖREN STOCKHOLM FÖRHANDL 82, 218–26.CrossRefGoogle Scholar
Norrish, K. & Chappell, B. W. 1977. X-ray fluorescence spectrography. In Zussman, J. (ed.) Physical methods in determinative mineralogy, 201–72. London: Academic Press.Google Scholar
Oliver, G. J. H. & Leggett, J. K. 1980. Metamorphism in an accretionary prism: prehnite-pumpellyite facies metamorphism of the Southern Uplands. TRANS R SOC EDINBURGH EARTH SCI 71, 235–46.CrossRefGoogle Scholar
Pearce, J. A. & Cann, J. R. 1973. Tectonic setting of basic volcanic rocks determined using trace element analysis. EARTH PLANET SCI LETT 19, 290–300.CrossRefGoogle Scholar
Petryk, A. A. 1981. Upper Ordovician glaciation: effects of eustatic fluctuations on the Anticosti platform succession, Quebec. In Lespérance, P. J. (ed.) Field meeting, Anticosti-Gaspe, Quebec, 1981 Vol. 2: Stratigraphy and paleontology, 81–5. Montreal: Department of Geology, University of Montreal.Google Scholar
Roguon, P. & de Charpal, O. 1968. Les glaciations ‘Siluriennes’ dans l' Ahnet et le Mouydir (Sahara central). PUBL SERV GEOL ALGERIE BULL 38.Google Scholar
Jia-Yu, Rong 1979. The Hirnantia fauna of China with comments on the Ordovician-Silurian boundary. ACTA STRATIGR SINICA 3, 1–8.Google Scholar
Jia-Yu, Rong 1984. Distribution of the Hirnantia fauna and its meaning. In Bruton, D. L. (ed.) Aspects of the Ordovician system, 101–12. PALAEONT CONTRIB UNIV OSLO 295. Oslo: Universitetsforlaget.Google Scholar
Ross, C. S. & Shannon, E. V. 1926. The minerals of bentonites and related clays and their physical properties. AM CERAM SOC J 9, 77–96.CrossRefGoogle Scholar
Sarna-Wojcicki, A. M., Meyer, C. E., Woodward, M. J. & Lamothe, P. J. 1981a. Composition of air-fall ash erupted on May 18, May 25, June 12, July 22 and August 7. In Lipman, P. W. & Mullineaux, D. R. (eds) The 1980 eruptions of Mount St Helens, Washington. US GEOL SURV PROF PAP 1250, 667–81.Google Scholar
Sarna-Wojcicki, A. M., Shipley, S., Waitt, R. B. jr, Dzurisin, D. & Wood, S. H. 1981b. Areal distribution, thickness, mass, volume and grain size of air-fall ash from the six major eruptions of 1980. In Lipman, P. W. & Mullineaux, D. R. (eds) The 1980 eruptions of Mount St Helens, Washington. US GEOL SURV PROF PAP 1250, 577–600.Google Scholar
Sheehan, P. M. 1973. The relation of Late Ordovician glaciation to the Ordovician-Silurian changeover in North American brachiopod faunas. LETHAIA 6, 147–54.CrossRefGoogle Scholar
Sheehan, P. M. 1975. Brachiopod synecology in a time of crisis (Late Ordovician-Early Silurian). PALAEOBIOLOGY 1, 205–12.CrossRefGoogle Scholar
Skevington, D. 1978. Latitudinal surface water temperature gradients and Ordovician faunal provinces. ARCHERINGA 2, 21–6.CrossRefGoogle Scholar
Spjeldnaes, N. 1961. Ordovician climatic zones. NOR GEOL TIDSSKR 41, 45–77.Google Scholar
Spjeldnaes, N. 1967. The palaeogeography of the Tethyan region during the Ordovician. In Aspects of Tethyan biogeography. SYST ASS PUB 7, 45–57.Google Scholar
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, 753–764.CrossRefGoogle Scholar
Sun, S-S., Nesbitt, R. W. & Sharaskin, A. Ya. 1979. Geochemical characteristics of mid-ocean ridge basalts. EARTH PLANET SCI LETT 44, 119–38.CrossRefGoogle Scholar
Teale, C. T. & Spears, D. A. 1986. The mineralogy and origin of some Silurian bentonites, Welsh Borderland, UK SEDIMENTOL 33, 757–65.CrossRefGoogle Scholar
Thirlwall, M. F. 1980. Peralkaline rhyolites from the Ordovician Tweeddale lavas, Peeblesshire, Scotland. GEOL J 16, 41–4.CrossRefGoogle Scholar
Thompson, R. N., Morrison, M. A., Hendry, G. L. & Parry, S. J. 1984. An assessment of the relative roles of crust and mantle in magma genesis: an elemental approach. PHILOS TRANS R SOC LONDON A310, 549–90.Google Scholar
Thorez, J. 1976. Practical identification of clay minerals. Belgium: G. Lalotte.Google Scholar
Thorslund, P. 1948. The Chasmops Series of the Kullatorp core. In Deep boring through Ordovician and Silurian strata at Kinnekulle, Vestergotland.BULL GEOL INST UPPSALA 32, 343–73.Google Scholar
Toghill, P. 1968. The graptolite assemblages and zones of the Birkhill Shales (Lower Silurian) at Dobb's Linn. PALAEONTOLOGY 11, 654–68.Google Scholar
Toghill, P. 1970. Highest Ordovician (Hartfell Shales) graptolitic faunas from the Moffat area, south-west Scotland. BULL BRIT MUS NAT HIST GEOL 19, 1–26.Google Scholar
Vogt, T. 1945. The geology of part of the Hølonda—Horg district, a type area in the Trondheim region. NOR GEOL TIDSSKR 25, 449–528.Google Scholar
Walton, E. K. 1963. Sedimentation and structure in the Southern Uplands. In Johnson, M. R. W. & Stewart, F. H. (eds) The British Caledonides, 71–97. Edinburgh: Oliver & Boyd.Google Scholar
Walton, E. K. 1965. Lower Palaeozoic rocks—stratigraphy and structure. In Craig, G. Y. (ed.) The geology of Scotland (1st edn), 161–227. Edinburgh: Oliver & Boyd.Google Scholar
Watson, S. W. 1976. The sedimentary geochemistry of the Moffat Shales, a carbonaceous sequence in the Southern Uplands. Unpublished Ph.D. Thesis, St Andrews University.Google Scholar
Welton, J. E. 1984. Scanning electron microscopy atlas. Tulsa: American Association of Petroleum Geologists.Google Scholar
Weir, J. A. 1973. Lower Palaeozoic graptolitic facies in Ireland and Scotland: review, correlation, and palaeogeography. SCI PROC R DUBL SOC SER A 4, 439–60.Google Scholar
Williams, A., Strachan, I., Bassett, D. A., Dean, W. T., Ingham, J. K., Wright, A. D. & Whittington, H. B. 1972. A correlation of Ordovician rocks in the British Isles. GEOL SOC LONDON SPEC REP 3.Google Scholar
Williams, D. M. 1979. The Maumtrasna Formation: possible indicators of Ordovician glacial activity in western Ireland. J EARTH SCI R DUBLIN SOC 2, 15–22.Google Scholar
Williams, S. H. 1982a. Upper Ordovician graptolites from the top lower Hartfell Shale Formation (D. clingani and P. linearis Zones) near Moffat, southern Scotland. TRANS R SOC EDINBURGH EARTH SCI 72, 229–55.CrossRefGoogle Scholar
Williams, S. H. 1982b. The Late Ordovician graptolitic fauna of the Anceps bands at Dob's Linn, southern Scotland. GEOL ET PALAEONTOL 16, 29–56.Google Scholar
Williams, S. H. 1983. The Ordovician-Silurian boundary graptolitic fauna of Dob's Linn, southern Scotland. PALAEONTOLOGY 26, 605–39.Google Scholar
Williams, S. H. 1987. Upper Ordovician graptolites from the D. complanatus Zone of the Moffat and Girvan districts and their significance for correlation. SCOTT J GEOL 23, 65–92.CrossRefGoogle Scholar
Williams, S. H. & Bruton, D. L. 1983. The Caradoc-Ashgill boundary in the central Oslo region and associated graptolite faunas. NOR GEOL TIDSSKR 63, 147–91.Google Scholar
Winchester, J. A. & Floyd, P. A. 1976. Geochemical magma type discrimination: application to altered and metamorphosed basic igneous rocks. EARTH PLANET SCI LETT 28, 459–69.CrossRefGoogle Scholar
Winchester, J. A. & Floyd, P. A. 1977. Geochemical discrimination of different series and their differentiation products using immobile elements. CHEM GEOL 20, 325–43.CrossRefGoogle Scholar
Ziegler, A. M., Scotese, C. R., Johnson, M. E., McKerrow, W. S. & Bambach, R. K. 1979. Palaeozoic palaeogeography. ANN REV EARTH PLANET SCI 7, 473–502.CrossRefGoogle Scholar
Zielinski, R. A. 1982. The mobility of uranium and other elements during alteration of rhyolite ash to montmorillonite: a case study in the Troublesome Formation, Colorado. CHEM GEOL 35, 185–204.CrossRefGoogle Scholar