Skip to main content Accessibility help

Evidence for late Ordovician amalgamation of volcanogenic terranes in the Iapetus suture zone, eastern Ireland

  • Finbarr C. Murphy (a1)


A major transcurrent fault in the zone of the Iapetus suture in eastern Ireland separates Ordovician (pre-Ashgill) terranes. The stratigraphy of each terrane belongs to a dismembered volcanic arc system: the northern terrane is characterised by acid plinian eruptions and derivative sediments which are displaced relative to the andesitic southern terrane volcanism. Each was a separate palaeoenvironment with its own lithostratigraphical character and faunal elements which were juxtaposed across the fault. However, the late Ashgill to Silurian sediments in both terranes form part of a regional overstep sequence which links across the suture zone, such that the palaeogeographical contrasts were eliminated by the Silurian. The inference is that the detached terranes were gradually amalgamated by late Ordovician transtensional movements. This occurred when regional scale subduction-related volcanism had ended. Final assembly by early Devonian sinistral transpressive movements juxtaposed a northern terrane, akin to the Lake District/SE Ireland calcalkaline volcanic province, with a southern terrane in the tholeiitic province of eastern Ireland. As distinct from a singular fault trace, the Iapetus suture is regarded as a 100 km wide zone of anastomosing late Caledonian transcurrent faults whose precursors were active during late Ordovician (i.e. Taconic) terrane amalgamation.



Hide All
Arnott, R. J., McKerrow, W. S. & Cocks, L. R. M. 1985. The tectonics and depositional history of the Ordovician and Silurian rocks of Notre Dame Bay, Newfoundland. CAN J EARTH SCI 22, 607618.
Bailey, D. K. & Halliday, D. K. 1962. Pillow-Lava Breccias and submarine sliding of pillow lavas. ABSTR GEOL SOC AM 107.
Bergström, S. M. 1983. Biogeography, evolutionary relationships and biostratigraphic significance of Ordovician platform conodonts. FOSSILS STRATA 15, 3558.
Bluck, B. J. & Leake, B. E. 1986. Late Ordovician to Early Silurian amalgamation of the Dalradian and adjacent Ordovician rocks in the British Isles. GEOLOGY 14, 917919.
Brenchley, P. J., Harper, J. C., Mitchell, W. I. & Romano, O. 1977. A reappraisal of some Ordovician successions in Eastern Ireland. PROC R IRISH ACAD 77, 6585.
Brück, P. M., Colthurst, J. R., Feeley, M., Gardiner, P. R. R., Penney, S. R., Reeves, T. J., Shannon, P. M., Smith, D. G. & Vanguestaine, M. 1979. Southeast Ireland: Lower Palaeozoic stratigraphy and depositional history. In Harris, A. L., Holland, C. H. and Leake, B. E. (eds) Caledonides of the British Isles—reviewed. GEOL SOC LONDON SPEC PUBL 8, 533544.
Brück, P. M. & Kennan, P. S. 1970. The Geology of Shenick's Island, Skerries, Co. Dublin. SCI PROC R DUBLIN SOC A3, 323333.
Carlisle, D. 1963. Pillow breccias and their aquagene tuffs, Quadra Island, British Columbia. J GEOL 71, 4871.
Chapin, C. E. & Elston, W. E. 1979. Ash-flow tuffs. SPEC PAP GEOL SOC AM 180.
Fitton, J. G. & Hughes, D. J. 1970. Volcanism and Plate Tectonics in the British Ordovician. EARTH PLANET SCI LETT 8, 223228.
France, D. S. 1967. The Geology of Ordovician rocks at Balbriggan, Co. Dublin, Eire. GEOL J 5, 291304.
Furness, H. 1972. Meta-Hyaloclastite breccias associated with Ordovician pillow lavas in the Solund area. West Norway. NOR GEOL TIDSSKR 52, 385407.
Harper, D. A. T. & Mitchell, W. I. 1982. Upper Ordovician (Ashgill) Brachiopods from the Oriel Brook Formation, County Louth. J EARTH SCI R DUBLIN SOC 5, 3135.
Harper, D. A. T., Mitchell, W. I., Owen, A. W. & Romano, M. 1984. Upper Ordovician brachiopods and trilobites from the Clashford House Formation near Herbertstown, Co. Meath, Ireland. BULL BR MUS NAT HIST (GEOL) 38, 287308.
Harper, J. C. & Rast, N. 1964. The faunal succession and volcanic rocks of the Ordovician near Bellewstown, Co. Meath. PROC R IRISH ACAD B64, 123.
Holland, C. H. 1981. A Geology of Ireland. Edinburgh: Scottish Academic Press.
Holland, C. H., Kelling, G. & Walton, E. K. 1979. O. T. Jones and after: a multitude of models. In Harris, A. L., Holland, C. H. and Leake, B. E. (eds) Caledonides of the British Isles—reviewed. GEOL SOC LOND SPEC PUBL 8, 469481.
Hull, E., Cruise, R. J. & Baily, W. H. 1871. Explanatory memoir to accompany sheets 91 and 92 of the maps of the Geological Survey of Ireland illustrating parts of Meath, Louth and Dublin. MEM GEOL SURV IRELAND.
Hutton, D. H. W. & Dewey, J. F. 1986. Palaeozoic Terrane accretion in the western Irish Caledonides. TECTONICS 5, 11151124.
Hutton, D. H. W., & Murphy, F. C. 1987. The Silurian rocks of the Southern Uplands and Ireland as a successor basin to the end Ordovician closure of Iapetus. J GEOL SOC LONDON 144 (in press).
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 3.
Jackson, D. 1978. The Skiddaw Group, In Moseley, F., (ed.) The Geology of the Lake District. YORKSHIRE GEOL SOC 3.
Kennan, P. S. & Kennedy, M. J. 1983. Coticules—a key to regional correlation along the Appalachian–Caledonian orogen? In Schenk, P. E. (ed.) Regional Trends in the geology of the Appalachian-Caledonian–Hercynian–Mauritanide Orogen, pp. 355361. Dordrecht: D. Reidel Publishing Company.
Kokelaar, B. P. 1982. Fluidization of wet sediments during the emplacement and cooling of various igneous bodies. J GEOL SOC LONDON 139, 2133.
Leggett, J. K., McKerrow, W. S. & Soper, N. J. 1983. A model for the crustal evolution of southern Scotland. TECTONICS 2, 187210.
Maltman, A. J. 1981. Primary bedding-parallel fabrics in structural geology. J GEOL SOC LONDON 138, 475483.
Mason, J. 1961. The geology of the Lower Palaeozoic rocks around Balbriggan, North County Dublin. M.Sc. Thesis, The Queens University of Belfast.
McKee, K. 1976. The Geology of the Lower Palaeozoic rocks around Bellewstown, Co. Meath, Eire. Unpublished M.Sc. Thesis, National University of Ireland.
McKerrow, W. S. & Cocks, I. R. M. 1976. Progressive faunal migration across the Iapetus ocean. NATURE 263, 304306.
Millward, D., Moseley, F. & Soper, N. J. 1978. The Eycott and Borrowdale Volcanic rocks. In Moseley, F. (ed.) The geology of the Lake District. YORKSHIRE GEOL SOC 3.
Morris, J. H. 1987. The Northern Belt of the Longford-Down, Ireland and Southern Uplands, Scotland: an Ordovician back arc basin. J GEOL SOC LONDON 144 (in press).
Moseley, F. 1977. Caledonian plate tectonics and the place of the English Lake district. BULL GEOL SOC AM 88, 704768.
Moseley, F. 1984. Lower Palaeozoic lithostratigraphical classification in the English Lake district. GEOL J 19, 239247.
Murphy, F. C. 1984a. Fluidized breccias: a record of brittle transitions during ductile deformation. TECTONOPHYSICS 104, 325349.
Murphy, F. C. 1984b. The lower Palaeozoic stratigraphy and structural geology of the Balbriggan Inlier, Counties Meath and Dublin. (Unpublished Ph.D. Thesis, University of Dublin).
Murphy, F. C. 1985. Non-axial planar cleavage and Caledonian sinistral transpression in Eastern Ireland. GEOL J 20, 257279.
Murphy, F. C. 1987. Late Caledonian granitoids and timing of deformation in the Iapetus suture zone of Eastern Ireland. GEOL MAG 124, 135142.
Murphy, F. C. & Hutton, D. H. W. 1986a. Is the Southern Uplands of Scotland really an accretionary prism? GEOLOGY 14, 354357.
Murphy, F. C. & Hutton, D. H. W. 1986b. Replies to Comments on “Is the Southern Uplands of Scotland really an accretionary prism?” GEOLOGY 14, 10431048.
Pettijohn, F. J. 1975. Sedimentary rocks. New York: Harper International.
Phillips, W. E. A., Stillman, C. J. & Murphy, T. 1976. A Caledonian plate tectonic model. J GEOL SOC LONDON 132, 579609.
Rickards, R. B., Burns, V. & Archer, J. 1973. The Silurian sequence at Balbriggan, Co. Dublin. PROC R IRISH ACAD B73, 303316.
Robinson, K. W. 1971. Gravity and magnetic investigations of the area between Lambay Island and Kildare, Eastern Ireland. Unpublished Ph.D. Thesis, University of Dublin.
Romano, M. 1970. The stratigraphy and palaeontology of the Ordovician rocks of eastern central Ireland. Unpublished Ph.D. Thesis, University of Liverpool.
Romano, M. 1980a. The stratigraphy of the Ordovician rocks between Slane (Co. Meath) and Collon (Co. Louth), Ireland. J EARTH SCI R DUBLIN SOC 3, 5379.
Romano, M. 1980b. The Ordovician rocks around Herbertstown (Co. Meath) and their correlation with the succession at Balbriggan (Co. Dublin), Ireland. J EARTH SCI R DUBLIN SOC 3, 205215.
Sigvaldson, G. E. 1968. Structure and products of subaquatic volcanoes in Iceland. CONTRIB MINERAL PETROL 18, 116.
Simpson, S. 1956. On the trace-fossil Chondrites. Q J GEOL SOC 112(4), 475.
Soper, N. J. & Hutton, D. H. W. 1984. Late Caledonian Sinistral displacements in Britain: Implications for a three plate collision model. TECTONICS 3, 781794.
Soper, N. J. & Nueman, N. M. S. 1974. Structure and stratigraphy of the Borrowdale Volcanic rocks of the Kentmere area, English Lake District. GEOL J 9, 147166.
Sparks, R. S. J., Self, S. & Walker, G. P. L. 1973. Products of Ignimbrite Eruptions. GEOLOGY 1, 115118.
Stanley, D. J. & Unrug, R. 1971. Submarine channel deposits, fluxoturbidites and other indicators of slope and base-of-slope environments in modern and ancient marine basins. In Rigby, J. K. and Hamblin, W. K. (eds) Recognition of ancient sedimentary environments. SOC ECON PALAEONT MINERAL SPEC PUBL 16, 287340.
Stillman, C. J., Downes, K. & Schiner, E. J., 1974. Caradocian Volcanic activity in east and south-east Ireland. SCI PROC R DUBLIN SOC 5A, 8798.
Stillman, C. J. & Williams, C. T. 1978. Geochemistry and tectonic setting of some Upper Ordovician volcanic rocks in east and southeast Ireland. EARTH PLANET SCI LETT 41, 288310.
Sylvestri, S. C. 1963. Proposal for a genetic classification of hyaloclastites. BULL VOLCANOL 25, 315321.
Wadge, A. 1978. Classification and stratigraphical relationships of the Lower Ordovician rocks. In Moseley, F. (ed) The Geology of the Lake District. YORKSHIRE GEOL SOC 3.
Williams, A., Strachan, I., Bassett, D. A., Dean, W. T., Ingham, J. K., Wright, A. D. & Whittington, H. B. 1976. A correlation of Ordovician rocks in the British Isles. GEOL SOC SPEC REP 3.
Williams, H. 1979. Appalachian orogen in Canada. CAN J EARTH SCI 16, 792807.
Woodcock, N. H. 1984. Early Palaeozoic sedimentation and tectonics in Wales. PROC GEOL ASSOC 95, 323335.
Wright, A. D. 1970. The stratigraphic distribution of the Ordovician brachiopod Orthisocrania divaricata (M'Coy) in the British Isles. GEOL MAG 107, 97103.


Evidence for late Ordovician amalgamation of volcanogenic terranes in the Iapetus suture zone, eastern Ireland

  • Finbarr C. Murphy (a1)


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