Ordovician rhynchonelliformean brachiopods from Co ...€¦ · Ordovician rhynchonelliformean brachiopods from Co. Waterford, SE Ireland: Palaeobiogeography of the Leinster Terrane

Ordovician rhynchonelliformean brachiopods from Co Waterford SE Ireland Palaeobiogeography of the

Leinster Terrane

by

Maria Liljeroth David A T Harper Hilary Carlisle and Arne T Nielsen

AcknowledgementsFinancial support for the publication of this issue of Fossils and Strata

was provided by the Lethaia Foundation

Introduction 1Previous work 2Geological setting 3Tectonic history of Ganderia and Avalonia 4Th e Iapetus Ocean 5Ireland 6

Th e Leinster Terrane 7Docking history 7Th e Tramore area 7

Material 9Stratigraphy and fauna 9

Age of the Tramore Limestone Formation 9Tramore and DunabrattinBunmahon sections 10

Tramore Shale Formation ndash Tramore area 12Tramore Limestone Formation ndash type section at Barrel

Strand Tramore area 12Lithology 12Fauna associations 14

Tramore Limestone Formation ndash other sections 14Pickardstown sections (Ps) 14 Quillia Section 1 (QS1) 14Quillia Section 2 (QS2) 14

Bunmahon Formation ndash BunmahonDunabrattin area 15Dunabrattin Shale Formation ndash BunmahonDunabrattin

area 15Dunabrattin Limestone Formation ndash Bunmahon

Dunabrattin area 15Lithology and fauna 16

Correlation 16Depositional setting and ecology 17

Local events 17Tramore Limestone Formation 17Dunabrattin Limestone Formation 19

Palaeobiogeographical reconstructions 20New reconstructions for the Iapetus Ocean 22

Ganderian terrane positions 22Longitudinal separation 22Latitudinal drift of the Ganderian-Avalonian segment 22

Brachiopod provinces 24Faunal distribution 24Darriwilian provinces and faunas 26

Th e Low-latitude Province on the Laurentian Platform 26An early Scoto-Appalachian fauna 27Th e Toquima-Table Head province 28Th e mixed faunas of the Leinster Terrane and

East Avalonia 31Th e Leinster Terrane 31East Avalonia 32

Th e Celtic province 32Th e Baltic Province 34Th e High-latitude Province 35

Darriwilian faunal migration patterns implications on oceanic current confi guration 35Migrations from the Laurentian margins and

intraoceanic islands to the south IapetusndashTornquist region 38

Migrations within the south IapetusndashTornquist region 38Th e Rheic gyre and the High-latitude Province 40Th e Precordillera 40

Early Sandbian brachiopod provinces 41Th e Low-latitude Province on the Laurentian Platform 41Th e Scoto-Appalachian Province 42Th e Anglo-WelshndashBaltic Province 43

Th e Leinster Terrane 44East Avalonia and Anglesey 46Baltica 47

Th e High-latitude Province 48Th e Precordillera 48

Conclusions 48Systematic palaeontology 50

Abbreviations 50Repository 50

Statistical methods 50Allometric growth 50

Phylum Brachiopoda Dumeacuteril 1806 51Subphylum Rhynchonelliformea Williams Carlson

amp Brunton 1996 51Class Strophomenata Oumlpik 1934 51Order Strophomenida Oumlpik 1934 51Superfamily Strophomenoidea King 1846 51Family Strophomenidae King 1846 51Subfamily Strophomeninae King 1846 51

Genus Tetraphalerella Wang 1949 51Tetraphalerella sp 52

Subfamily Furcitellinae Williams 1965 53Genus Dactylogonia Ulrich amp Cooper 1942 53

Dactylogonia costellata n sp 53Family Rafi nesquinidae Schuchert 1893 55Subfamily Rafi nesquininae Schuchert 1893 55

Genus Colaptomena Cooper 1956 55Colaptomena auduni n sp 56Colaptomena pseudopecten (MrsquoCoy 1846) 57

Superfamily Plectambonitoidea Jones 1928 59Family Plectambonitidae Jones 1928 59Subfamily Taphrodontinae Cooper 1956 59

Genus Isophragma Cooper 1956 59Isophragma parallelum n sp 59

Family Leptellinidae Ulrich amp Cooper 1936 61Subfamily Leptellininae Ulrich amp Cooper 1936 61

Genus Leptellina Ulrich amp Cooper 1936 61Leptellina llandeiloensis (Davidson 1883) 61

Subfamily Palaeostrophomeninae Cocks amp Rong 1989 62Genus Glyptambonites Cooper 1956 62

Glyptambonites sp 62Family Grorudiidae Cocks amp Rong 1989 63

Genus Grorudia Spjeldnaeligs 1957 63Grorudia grorudi Spjeldnaeligs 1957 63

Family Leptestiidae Oumlpik 1933a emend Cocks amp Rong 1989 64Genus Leptestiina Oumlpik 1933a 64

Leptestiina derfelensis (Jones 1928) 65Family Sowerbyellidae Oumlpik 1930 66Subfamily Sowerbyellinae Oumlpik 1930 66

Genus Sowerbyella Jones 1928 66Subgenus Sowerbyella (Sowerbyella) Jones 1928 66

Sowerbyella (Sowerbyella) antiqua Jones 1928 66Order Billingsellida Schuchert 1893 70Suborder Clitambonitidina Oumlpik 1934 70Superfamily Clitambonitoidea Winchell amp Schuchert 1893 70Family Clitambonitidae Winchell amp Schuchert 1893 70

Genus Atelelasma Cooper 1956 70Atelelasma longisulcum n sp 70

Class Rhynchonellata Williams Carlson amp Brunton 1996 73Order Orthida Schuchert amp Cooper 1932 73Suborder Orthidina Schuchert amp Cooper 1932 73Superfamily Orthoidea Woodward 1852 73Family Orthidae Woodward 1852 73

Genus Sulevorthis Jaanusson amp Bassettt 1993 73Sulevorthis aff S blountensis (Cooper 1956) 73

Family Glyptorthidae Schuchert and Cooper 1931 74Genus Glyptorthis Foerste 1914 74

Glyptorthis crispa (MrsquoCoy 1846) 74Family Hesperorthidae Schuchert amp Cooper 1931 77

Genus Hesperorthis Schuchert amp Cooper 1931 77Hesperorthis leinsterensis n sp 77

Family Plaesiomyidae Schuchert 1913 86Subfamily Plaesiomyinae Schuchert 1913 86

Genus Valcourea Raymond 1911 86Valcourea confinis (Salter 1849) 86

Family Productorthidae Schuchert amp Cooper 1931 87Subfamily Productorthinae Schuchert amp Cooper 1931 87

Genus Productorthis Kozłowski 1927 87Productorthis sp 87

Superfamily Plectorthoidea Schuchert amp LeVene 1929 89

Contents

Family Platystrophiidae Schuchert amp LeVene 1929 emend Zuykov amp Harper 2007 89Genus Platystrophia King 1850 emend Zuykov

amp Harper 2007 89Platystrophia tramorensis n sp 89Platystrophia aff P sublimis Oumlpik 1930 92

Suborder Dalmanellidina Moore 1952 94Superfamily Dalmanelloidea Schuchert 1913 94Family Dalmanellidae Schuchert 1913 94Subfamily Dalmanellinae Schuchert 1913 94

Genus Howellites Bancroft 1945 94Howellites hibernicus n sp 94

Family Paurorthidae Oumlpik 1933b 106Genus Paurorthis Schuchert amp Cooper 1931 106

Paurorthis aff P parva (Pander 1830) 106Superfamily Enteletoidea Waagen 1884 110

Family Linoporellidae Schuchert amp Cooper 1931 110Genus Salopia Williams in Whittington amp Williams 1955 110

Salopia gracilis Williams in Whittington amp Williams 1955 110

Order Pentamerida Schuchert amp Cooper 1931 111Suborder Syntrophiidina Ulrich amp Cooper 1936 111Superfamily Syntrophioidea Ulrich amp Cooper 1936 111Family Porambonitidae Ulrich amp Cooper 1936 111

Genus Hibernobonites n gen 111Hibernobonites filosus (MrsquoCoy 1846) 112

Acknowledgements 115References115Plates 1ndash10 122Appendix A 142 Appendix B 148

Ordovician rhynchonelliformean brachiopods from CoWaterford SE Ireland palaeobiogeography of the LeinsterTerraneMARIA LILJEROTH DAVID AT HARPER HILARY CARLISLE AND ARNE T NIELSEN

Liljeroth M Harper DAT Carlisle H amp Nielsen AT 2017 Ordovicianrhynchonelliformean brachiopods from Co Waterford SE Irelandpalaeobiogeography of the Leinster Terrane Fossils and Strata No 62 pp 1 164 doi10111let12205

The Irish Leinster Terrane Co Waterford SE Ireland has traditionally been associ-ated with a palaeogeographical position close to East Avalonia but a number of recentstudies on for example zircon geochronology geochemistry isotope analyses and tec-tono- and lithostratigraphy strongly point to a Ganderian affinity Together with theMonian Composite Bellewstown Grangegeeth Central Newfoundland and Mirami-chi terranes the Leinster Terrane formed part of the leading edge of Ganderia in asso-ciation with the Popelogan-Victoria arc several hundred kilometres north of Avaloniaduring the Ordovician The present faunal data together with the Ganderian studiesand compiled palaeomagnetic data from other authors form the basis of new palaeo-biogeographical reconstructions of the mid Darriwilian and early Sandbian palaeo-plate configurations in the south Iapetus Ocean The generic composition of theTramore and Dunabrattin Limestone formations contains only few endemic formsand is dominated by a mix of taxa that originated in other parts of the world duringthe Early early Late Ordovician including low-latitude Laurentia high-latitude peri-Gondwana and mid-latitude Baltica All the Ganderian terranes and East Avaloniacontained mixed faunas during the mid Darriwilian early Sandbian indicating thatthese sites together occupied a mid-latitudinal position comprising settling groundsfor taxa from the surrounding widely dispersed high- low- and mid-latitude palaeo-plates The Tramore and Dunabrattin limestones furthermore contain brachiopodspecies that migrated to the Leinster Terrane from East Avalonia Baltica Laurentiaand peri-Laurentia during the late Darriwilian early Sandbian confirming the Gan-derian terranersquos close relationship with the other Iapetus-bordering sites Oceanicwind-driven surface currents were the primary factor determining brachiopod disper-sal in the Darriwilian when the majority of taxa were associated with shelfal biofaciesThe brachiopod migrational patterns reported for the Darriwilian in the present inves-tigation together with the Mid Ordovician synthetic ocean surface circulation modelsform the basis of revised models of oceanic surface current flow for the early and lateDarriwilian respectively The gracilis drowning diminished brachiopod provincialityin the early Sandbian and the number of reported brachiopod provinces was reducedfrom five to four The mid-latitude Celtic and Baltic provinces were thus obliteratedand replaced by the combined Anglo-Welsh Baltic Province A total of 20 rhynchonel-liformean brachiopod genera and 22 species are described from the upper Darriwilian

lower Sandbian Tramore and Dunabrattin Limestone formations (Leinster Terrane)Seven of these are new species and include Atelelasma longisulcum n sp Colaptomenaauduni n sp Dactylogonia costellata n sp Hesperorthis leinsterensis n sp Howelliteshibernicus n sp Isophragma parallelum n sp and Platystrophia tramorensis n sp aswell as one new genus Hibernobonites n gen and the earliest recorded occurrence of aTetraphalerella-like genus in the lowermost part of the Tramore Limestone Avalo-nia biogeography brachiopods Darriwilian Ganderia Leinster Terrane oceanic surfacecurrents Sandbian

Maria Liljeroth [foramsergmailcom] DK-7950 Erslev Mors North Jutland DenmarkDavid AT Harper [davidharperdurhamacuk] Palaeoecosystems Group Departmentof Earth Sciences Durham University Durham DH1 3LE UK Hilary Carlisle [hcarlisle-belfastgmailcom] Osborne Park Belfast BT9 6JN UK Arne T Nielsen [ar-netignkudk] Department of Geosciences and Natural Resource Management OslashsterVoldgade 10 DK-1350 Copenhagen Denmark manuscript received on 6032016 manu-script accepted on 12122016

IntroductionThe current work comprises a description of therhynchonelliformean brachiopods from the upper

Darriwilian lower Sandbian Tramore LimestoneFormation and lower Sandbian Dunabrattin Lime-stone Formation Tramore area Co Waterfordsoutheast Ireland The stratigraphy of the formations

DOI 10111let12205 2017 Lethaia Foundation Published by John Wiley amp Sons Ltd

is updated with new lithological and faunal correla-tions between the formation units as well as bios-tratigraphical correlation with the international andBritish stages of Cooper amp Sadler (2012) and inter-national time-slices of Webby et al (2004) Newinterpretations regarding the depositional settingsand palaeoecology of the formations are likewiseprovided including a new lithologically based modelfor palaeobathymetric characterization

The Tramore fauna is unique in the sense that itcontains a mixed fauna of for example LaurentianBaltic and high-latitude peri-Gondwanan originswith no unequivocal relation to any of the definedbiogeographical provinces in the Darriwilian Thecomplex faunal composition of the DarriwilianSandbian Leinster Terrane has led some authors tosuggest a more oceanwards position for the terranethan traditionally applied that is within the leadingedge of East Avalonia (Owen amp Parkes 2000) or aseparate driftingdocking history (Fortey amp Cocks2003) The current work provides a detailed assess-ment of the brachiopod provinces described byHarper et al (2013) and the faunas related to theinvestigated palaeoplates with focus on the Iapetusand Rheic oceans and the Tornquist Sea not only toresolve the source of the mixed faunal signature ofthe Leinster Terrane but also to reveal importantdetails about the individual palaeoplates within theprovinces that have hitherto not been assessed bythe traditionally more general global biogeographi-cal analyses The two time-slices applied hereinmainly cover the early mid latest Darriwilian andthe early Sandbian respectively and largely includestratigraphy with a significant biostratigraphicaloverlap with the Tramore and Dunabrattin Lime-stone formations This is an attempt to study high-resolution brachiopod biogeography on a widergeographical scale within very limited time inter-vals Previous procedure for these investigationswithin the Darriwilian and Sandbian was often tocombine the Dapingian and Darriwilian into onetime-slice and to include the total Sandbian intervaldue to poor biostratigraphical constraint (see egHarper et al 2013) By implication not all strati-graphical sections overlapping with the late Darri-wilian or early Sandbian are included in themultivariate biogeographical analyses but the taxo-nomical compositions of the individual sites andprovinces within the time-slices are compared withlater and earlier faunas to give a more completepicture

The Leinster Terrane has traditionally been illus-trated as having close geographical proximity to EastAvalonia based on faunal affinities and the presenceof arc-related volcanic rocks (eg Parkes amp Harper

1996 Cocks et al 1997 Harper amp Mac Niocaill2002) but several analyses including detrital zircongeochronology geochemistry isotopic signatureslitho- and tectonostratigraphy and palaeomagnetism(eg van Staal et al 1996 1998 2009 2012 Collinsamp Buchan 2004 Valverde-Vaquero et al 2006 Hib-bard et al 2007 Fyffe et al 2009 Zagorevski et al2010 Pothier et al 2015 Waldron et al 2014) nowpoint to a position within the leading edge of Gan-deria close to the Popelogan-Victoria volcanic arctogether with the Monian Composite (ie Rosslareand Anglesey) Bellewstown Grangegeeth CentralNewfoundland and Miramichi terranes Based onthese results as well as compiled palaeomagnetic datafrom several authors (ie Torsvik et al 1990 19921996 van der Voo et al 1991 Trench amp Torsvik1992) the current study suggests new palaeobiogeo-graphical reconstructions for the Iapetus Ocean forthe mid Darriwilian and early Sandbian respec-tively

The Tramore fauna was not the only fauna ofmixed origins in the late Darriwilian In fact EastAvalonia and the Ganderian terranes contained vary-ing numbers of biogeographically important taxathat originated in different parts of the world includ-ing Laurentia peri-Laurentia and peri-Gondwanawith an additional significant Baltic component pre-sent in the Ganderian terranes not reported fromEast Avalonia This poses an interesting problemrelating to geographical position and oceanic surfacecurrent systems that when seen in context aidsexplanation of the faunal affinities of the LeinsterTerrane

The studied time-slices were part of the GreatOrdovician Biodiversification Event (GOBE) whenglobal marine diversity increased dramatically andthe rhynchonelliform brachiopods experiencedmajor diversification on family genus and specieslevel Orthide and strophomenide origination ratesexceeded extinction rates across the DarriwilianSandbian transition on a global scale (Harper et al2004) although the present high-resolution studyidentifies sites in which diversity declined across thetransition due to accelerated extinction and localizeddisappearance of specialized taxa

Previous workThe continuous succession of volcanic and sedimen-tary deposits now assigned to the Duncannon Groupwas first described by Reed (1899) from a localitynear Tramore town He drew several sketches alongthe foreshore showing the relation between the for-mations of the group including the Tramore

2 M Liljeroth et al FOSSILS AND STRATA

Limestone Formation Subsequent stratigraphicalaccounts by Mitchell et al (1972) Williams (1976)Carlisle (1979) Harper amp Parkes (2000) Wyse Jack-son et al (2001) and Key et al (2005) and this studywere based on the same area

The brachiopod faunas of the Duncannon Groupin County Waterford were described by Carlisle inMitchell et al (1972) and Carlisle (1979) The 1972paper gave a preliminary palaeontological andstratigraphical account of the Duncannon Groupformations and the 1979 paper summarizes Car-lislersquos main work with a reinterpretation of theTramore area faunas Parkes (1994) published amonographic work on the brachiopod systematicsfrom selected formations of the Duncannon Groupprimarily using Carlislersquos original material collectedin the Tramore area in the 1970s excluding theTramore and Dunabrattin Limestone formationsOther palaeontological work includes descriptionsof the bryozoans of the Tramore and Dunabrattinlimestones and their palaeoenvironmental affinities(Wyse Jackson et al 2001) a monographic workon the trilobites of the Duncannon Group pub-lished by Owen amp Parkes (2000) and a crinoiddescribed from the Tramore Limestone by Dono-van (1985)

The early work by Williams (1976) recognized adivision of Ireland based on the different faunalaffinities He divided the country into three distinctsouthwest northeast oriented belts largely corre-sponding to (1) the Irish part of the Midland ValleyTerrane (possibly together with the Grampian Ter-rane) of Scoto-Appalachian faunal affinity (2) theIrish part of the Southern Uplands Terrane with aSouthern Uplands faunal affinity and (3) the Lein-ster Terrane with Anglo-Welsh and Baltic affinitiesPalaeobiogeographical analyses of the Irish terraneswere provided by for example Harper amp Parkes(1989) Murphy et al (1991) Harper (1992) Parkes(1992) Owen amp Parkes (2000) and Key et al (2005)Harper amp Parkes (2000) recognized at least seventectonic terranes in Ireland based on faunal evidenceand the present study follows this division althoughwith terrane names from Waldron et al (2014) Anoverview of the palaeontological characteristics ofthe Irish terranes was provided by Harper amp Parkes(1989)

The tectonic evolution of the Iapetus Ocean wasdescribed in detail by van Staal et al (1996 19982009 2012) Zagorevski et al (2010) Pollock et al(2012) and Pothier et al (2015) Detailed accountsof the tectonic evolution of Avalonia and Ganderiawere given by van Staal et al (1996 1998 2009)Hibbard et al (2007) Pollock et al (2012) and Wal-dron et al (2014)

Geological settingThe Tramore and Dunabrattin Limestone forma-tions belong to the upper Darriwilian lowerKatian Duncannon Group of southeastern countiesWaterford and Wexford Ireland The DuncannonGroup comprises a suite of shallow- to deep-waterimpure carbonates and calcareous mudrocks over-lain by basaltic andesitic and rhyolitic arc vol-canics accumulated on the Leinster Terrane(Carlisle 1979 Harper amp Parkes 2000 Key et al2005)

Southeastern Ireland including the Leinster Ter-rane and the associated Leinster Basin formed partof the southern margin of the Iapetus Oceanthrough the Ordovician (eg Stillman 1978 Neu-man amp Harper 1992 Harper et al 1996 Mac Nio-caill et al 1997 van Staal et al 1998 2012 Harperamp Mac Niocaill 2002 Cocks amp Torsvik 20112013) Its Middle Upper Ordovician volcanic rockshave previously been associated with subductionrelated arc backarc volcanism by the leading edgethat is the northern margin of the Avalonianmicrocontinent (eg Phillips et al 1976 Stillman1986 Parkes 1992 Tietzsch-Tyler amp Sleeman 1994Sleeman amp McConnell 1995 Parkes amp Harper1996 Cocks et al 1997 Mac Niocaill et al 1997Harper amp Mac Niocaill 2002 Key et al 2005Brenchley amp Rawson 2006 Brenchley et al 2006Harper et al 2013) but recent results by otherworkers (see below) suggest that the volcanic rocksof the Leinster Terrane were more likely related toarc backarc volcanism in the Popelogan-Victoriaarc Tetagouche-Exploits backarc basin (PVA-TEB)by the leading edge of the Ganderian microconti-nent north of Avalonia Owen amp Parkes (2000)stressed that the Leinster Terrane had a more com-plex tectonic and biogeographical relationship withthe Anglo-Welsh area than previously considered(ie by workers placing the terrane close to thenorthern East Avalonian margin) and suggested amore oceanwards position of this terrane Fortey ampCocks (2003) suggested it had a separate driftingdocking history to East Avalonia based on bra-chiopod and trilobite faunas although they illus-trated the terrane as positioned on the northernEast Avalonian margin

Tectonomagmatic analyses of West Avalonian andwest Ganderian basement rocks in the Appalachianorogen by Barr amp White (1996) showed that Avalo-nia and Ganderia have different basement composi-tion Several other authors applying one or more ofthe following types of data and methods includingdetrital zircon geochronology geochemistry iso-topic signatures litho- and tectonostratigraphy and

FOSSILS AND STRATA Ordovician brachiopods from SE Ireland 3

palaeomagnetism (eg van Staal et al 1996 19982009 2012 Collins amp Buchan 2004 Valverde-Vaquero et al 2006 Hibbard et al 2007 Fyffe et al2009 Zagorevski et al 2010 Pothier et al 2015Waldron et al 2014) identified Ganderia and itsassociated islands and volcanic arc terranes andorthe mutual palaeogeographical relationship betweena selection of these and other terranes and micro-continents Pollock et al (2012) reviewed thepalaeogeographical development of the peri-Gond-wanan realm of the Appalachian orogeny includingthe history of Ganderia and Avalonia and summa-rized their definitions

The regional distribution of Ganderia and Aval-onia in Ireland and Great Britain is shown by Pol-lock et al (2012 fig 4) Terranes included inGanderia are the Bellewstown (east Ireland) Gran-gegeeth (east Ireland) and Leinster Lakesman(south Ireland north England) terranes and theMonian Composite Terrane (Anglesey of northwestWales and Rosslare of southeast Ireland) TheSouthern Uplands Terrane was also included inGanderia by Pollock et al (2012) but zircongeochronology studies by Waldron et al (2014)strongly suggested a Laurentian affinity for the ter-rane The regional distributions of the northernAppalachian terranes associated with Ganderia areillustrated in Pollock et al (2012 fig 3) andinclude the Central Newfoundland and Miramichi(New Brunswick Maine) terranes Following theresults of van Staal et al (1996 1998 2009 2012)these terranes formed part of the Popelogan-Vic-toria arc Tetagouche-Exploits backarc basin systemcreated by subduction at the leading edge of Gan-deria during the progressive closure of the IapetusOcean Harper amp Mac Niocaill (2002) associatedthe Central Newfoundland and Miramichi terranesof Ganderia with the western part of the Popelo-gan-Victoria arc north of Avalonia but they stillincluded the Leinster and Monian Composite ter-ranes as part of the East Avalonian margin TheWelsh Basin of East Avalonia includes Tremado-cian arc volcanics but the development of thePopelogan-Victoria arc Tetagouche-Exploits back-arc basin system in the Floian (ca 475 Ma vanStaal et al 2012) changed both location and chem-istry of the volcanism and transformed the WelshBasin into a backarc basin (Brenchley amp Rawson2006 Brenchley et al 2006) The Leinster Terraneand Basin includes Sandbian acidic volcanics typi-cal of arc backarc volcanism and was locatedoceanwards of the Welsh and Anglian basins(Brenchley amp Rawson 2006) possibly in closeproximity to the Popelogan-Victoria arc

Tectonic history of Ganderia andAvaloniaGanderia and Avalonia are peri-Gondwanan micro-continents that were situated along the northernmargin of West Gondwana (Amazonia) and close toor juxtaposed against the West African marginrespectively in the late Neoproterozoic (Fyffe et al2009 van Staal et al 2009 2012 Pothier et al 2015Waldron et al 2014) Avalonia was situated at ca65 S during the mid late Cambrian with Ganderialocated north of this and with a present-day strikelength of at least 2500 km Ganderia may haveextended for over 23 of latitude allowing for a pos-sible along-strike connection with Avalonia (vanStaal et al 2012) The presence of the Cambriantrilobites Kootenia and Baliella in a limestone blockof the Dunnage Melange central Newfoundlandshows that Ganderia formed at high latitudes alongthe Gondwanan margin (Pollock et al 2012)

Ganderia started to separate from Amazoniaaround 505 Ma opening the northern arm of theRheic Ocean The Rheic Ocean may initially haveopened as a backarc basin with the Penobscot vol-canic arc positioned along the leading edge of Gan-deria from 584 to 515 Ma (Zagorevski et al 2010van Staal et al 2012) Subsequent dextral-obliquemotion moved most of Avalonia to a position justsouth of Ganderia along the Amazonian margin andcreated a narrow intervening seaway of trappedoceanic lithosphere between the two microconti-nents (van Staal et al 2012) Avalonia rifted fromGondwana in the late Tremadoc (479 Ma) (Murphyet al 2004) opening the southern arm of the RheicOcean (van Staal et al 2012) Comparable faunalassemblages support Gondwanan linkages with Aval-onia until the Tremadocian (Cocks et al 1997 For-tey amp Cocks 2003 Harper et al 2013) after whichthe faunal provinciality indicates changing affinitiesfrom Gondwanan to Laurentian (Harper et al2013)

The Popelogan-Victoria arc was initiated around475 Ma when subduction commenced again by theleading edge of Ganderia The volcanic arc existeduntil the collision with Laurentia in the late Sand-bian (van Staal et al 2012) or early Katian It mayhave extended from beyond the eastern tip of Gan-deria along its complete east west strike length con-tinuing into the Famatina arc to the west along thepresent-day western margin of South America (seevan Staal et al 2012) Subduction of Avaloniabeneath Ganderia took place during the Silurianearly Devonian after Ganderia had accreted to com-posite Laurentia


Calculated drift rates of ca 9 cma for the leadingedge of Ganderia (500 455 Ma) and for Avalonia(490 460 Ma) indicate that they were situated onthe same microplate after they had parted fromGondwana (van Staal et al 2012) and they subse-quently moved northeastwards by sinistral-obliquemovement towards Laurentia through the EarlyLate Ordovician (Pollock et al 2012) The latitudi-nal drift rate for Avalonia decreased to 5 cma by ca460 Ma which van Staal et al (2012) considered tobe a proxy for the drift rate of the trailing edge ofGanderia at this time The ca 4 cma discrepancy indrift rates between the Popelogan-Victoria arc andthe trailing Ganderia margin is attributed to riftingin the intervening Tetagouche-Exploits backarcbasin which initiated at ca 475 Ma when drift ratesof Ganderia and Avalonia slowed down (van Staalet al 2009) The rate discrepancy suggests a half-spreading rate of ca 2 cma in the Tetagouche-Exploits basin producing a 600- to 800-km-wideocean prior to 455 Ma (van Staal et al 2012)

Pothier et al (2015) presented an alternative tec-tonic model for Ganderia and Avalonia In their midCambrian (ca 500 Ma) and late Tremadocian (ca480 Ma) reconstructions Ganderia and Avalonia arerotated more than 90 counterclockwise with thepresent (palaeo)northern margin of Ganderia juxta-posed against Amazonia and the (palaeo)southernmargin of Avalonia facing eastwards towards anopen ocean with Baltica in the distance Pothieret al (2015) suggested that after Avalonia hadmoved to a position just north of Ganderia by sinis-tral transpression in the late Tremadocian Ganderiaand Avalonia (incl Meguma in which they includedNorth Wales and Nova Scotia) moved northwest-wards together along the Amazonian margin to leaveAmazonia at a latitude of about 30 S while rotatingclockwise to face the Laurentian margin Theirmodel was based on sediment provenance and a pos-sible sinistral movement of Avalonia north of Gan-deria the latter implying the necessity of placingthese microcontinents in an lsquoupside downrsquo orienta-tion relative to the Gondwanan margin The faunalanalyses of this study do not readily support theirmodel however as the Darriwilian Ganderian siteswould be expected to include less Laurentian andBaltic brachiopod genera and a higher proportion ofGondwanan taxa than reported The palaeomagneti-cally inferred latitudinal positions of central New-foundland and the Welsh Basin through the EarlyLate Ordovician described below do not supportthis either The reconstruction of van Staal et al(2012) does not contradict the influx of West Afri-can and Amazonian sediment to Meguma and Gan-deria respectively in the mid Cambrian and late

Tremadocian as inferred by Pothier et al (2015) asthey placed Meguma and Avalonia very close to theWest African margin and juxtaposed Ganderiaagainst Amazonia during these times

The Iapetus OceanThe Iapetus Ocean existed for about 170 millonyears (ca 580 420 Ma) and may have been as wideas 3000 5000 km estimated by faunal evidence andpalaeomagnetic records (eg Cocks amp Fortey 1982Fortey amp Cocks 1988 Harper 1992 Trench amp Tors-vik 1992 Harper et al 1996) Palaeomagnetic analy-ses place the Early Ordovician Scottish segment ofthe Laurentian margin in low southerly latitudes ofabout 15 20 S (Torsvik et al 1990 1996) and EastAvalonia about 60 S 5 10 the same latitude asthe West African margin (Channel et al 1992Trench et al 1992) The Miramichi Terrane mayhave been positioned at ca 53 S in the early midDarriwilian although the age constraint on the Mira-michi Group from which this palaeolatitude wasobtained is not very precise (see McNicoll et al2002) During the Floian Avalonia had moved to aposition of about 41 S 8 (Pollock et al 2012) andin the latest Floian (470 Ma) palaeomagnetic analy-ses by Van der Voo et al (1991) indicate that someCentral Newfoundland Terrane localities includingSummerford were at a latitudinal position of 31 S

8 corresponding to a minimum distance fromwest Newfoundland to the southern margin of Lau-rentia of ca 1500 km By this time the Laurentianmargin was positioned at about 15 S (Van der Vooet al 1991) Trench amp Torsvik (1992) estimated thatthe latitudinal distance between East Avalonia andthe peri-Laurentian terranes was reduced from ca5000 to 3300 km between the late Tremadocian andlatest Darriwilian and placed the Welsh Basin ofEast Avalonia at 45 S in the latest Darriwilian ear-liest Sandbian based on palaeomagnetic studies ofvolcanic rocks from this basin

The Iapetus Ocean closed due to northeastwarddrift of Ganderia and Avalonia towards latitudes ofabout 11 19 S in the Late Ordovician mid Silurian(van Staal et al 2012) which resulted in the collisionof a number of terranes and microcontinents andultimately the formation of the North AmericanAppalachians and the northwest European Scandi-navian and Greenland Caledonides The first sign ofinitial closure of the Iapetus Ocean was recorded inthe rocks from the north and south margins of theocean by the onset of volcanic activity in associationwith subduction of oceanic crust (Tietzsch-Tyler ampSleeman 1994) In southeast Ireland evidence of this


event is observed in the arc-associated volcanic rocksof the Lower Ordovician Maulin Formation (Rib-band Group) underlying the Duncannon Group andseparated from this by a hiatus (Tietzsch-Tyler ampSleeman 1994 Harper amp Parkes 2000 Key et al2005) The collisions involving Ganderia and Avalo-nia commenced with the arc arc collision of thewestern part of the Popelogan-Victoria arc andthe Red Indian Lake arc which at this time formedthe leading edge of the Laurentian plate during theTaconic Orogeny 3 (460 450 Ma) (van Staal et al2009) This was followed by the accretion of theactive leading edge of Ganderia to Laurentia andprogressive closure of the Tetagouche-Exploits back-arc basin during the Salinic Orogeny (450 423 Ma)and was concluded in the late Silurian Early Devo-nian (421 400 Ma) by the Acadian orogeny involv-ing accretion of Avalonia to Laurentia (van Staalet al 2009) The arc arc collision between the west-ern Popelogan-Victoria arc and Red Indian Lake arcis today represented by the Red Indian Line which isthe principal Iapetan suture in the northernAppalachians (van Staal et al 2009 Pollock et al2012)

IrelandThe presence of an Ordovician volcanic arc in south-east Ireland and the English Lake District have beenthe subject of discussion for many years (eg Phillipset al 1976 Stillman 1986 Tietzsch-Tyler amp Sleeman1994 Sleeman amp McConnell 1995 Key et al 2005Brenchley et al 2006) The Anglo-Irish part of thePopelogan-Victoria arc is represented by the pre-sent-day Longford-Down Inlier in Ireland and Eng-land (Fig 1) Earlier workers referred to the islandarc as the Irish Sea Horst (Williams 1969 Bevinset al 1992 Brenchley et al 2006) the Irish SeaLandmass (Fitton amp Hughes 1970 Phillips et al1976) or the Longford-Down arc (van Staal et al1998)

Ireland was formed by accretion of at least sevenarc terranes within the Iapetus Ocean during theOrdovician Silurian orogenies (Harper amp Parkes2000 see Fig 1) Faunal evidence from Harper ampParkes (1989) Parkes (1992) and Harper et al(2013) suggests that the South Mayo Terrane andthe Irish Scottish Midland Valley and SouthernUplands terranes occupied a peri-Laurentian

Fig 1 Map of Irish and British terranes An Anglesey BT Bellewstown Terrane GT Grangegeeth Terrane NHT Northern HighlandsTerrane RT Rosslare Terrane Modified from Woodcock (2000) and Waldron et al (2014)


position during the Ordovician and were associatedwith the Red Indian Lake volcanic arc by the north-ern border of the Iapetus Ocean A number of work-ers applying non-faunal data (eg van Staal et al1996 1998 2009 2012 Woodcock 2000 Collins ampBuchan 2004 Valverde-Vaquero et al 2006 Pollocket al 2012 Pothier et al 2015 Waldron et al 2014)associated the Leinster Lakesman Monian Compos-ite (Anglesey Rosslare) Bellewstown and Grange-geeth terranes with the leading edge of Ganderia(PVA-TEB) by the southern border of the IapetusOcean Together these terranes make up present-day Ireland and the Iapetus suture marks the bound-ary between the rocks formed in the north and southIapetus Ocean (Fig 1)

The Leinster TerraneThe Irish part of the Leinster Lakesman Terrane istermed the Leinster Terrane It makes up most of thesouthern part of Ireland (Fig 1) and covers an areaof 24 000 km2 (Murphy et al 1991) The LeinsterTerrane is bounded by the Irish Southern UplandsTerrane and the Bellewstown Terrane to the northand northeast respectively along major fault linesrunning from Dingle in the west to Bellewstown inthe east and by the Monian Composite Terrane rep-resented by the Rosslare Terrane to the southeast(Murphy et al 1991 Harper amp Parkes 2000 Wood-cock 2000 Waldron et al 2014) (Fig 1) The Eng-lish part of the Leinster Lakesman Terrane is termedthe Lakesman Terrane It extends northeast fromIreland through England along the southern borderof the Scottish Southern Uplands Terrane (Blucket al 1992 Woodcock 2000) Max et al (1990)divided the Leinster Terrane into five separate ter-ranes Harper amp Parkes (2000) noted however thatthe stratigraphical development across the terrane isbroadly similar and differences in facies may berelated to lateral facies changes rather than signifi-cant geographical separation

Docking historyThe amalgamation of the Irish terranes may havecommenced between the early Cambrian and theFloian with the docking of the Monian CompositeTerrane including the Anglesey and Rosslare ter-ranes onto the Leinster Lakesman part of Ganderia(van Staal et al 1998 Valverde-Vaquero et al 2006Pothier et al 2015) Pothier et al (2015) suggestedthat Monian deformation juxtaposed a portion ofGanderia probably represented by present-dayAnglesey against the margin of the Welsh Basin inEast Avalonia along the present-day Menai Strait

Fault System (Fig 1) causing an influx of lsquoMonianrsquodetritus into the Welsh Basin by the TremadocianFollowing van Staal et al (1998 2012) the WelshBasin gradually became separated from the Lein-ster Lakesman and Monian Composite terranes bythe initiation and continued development of theTetagouche-Exploits backarc basin from the Floianand onwards Derivation of sediment from theMonian Composite Terrane into the Welsh Basincontinued at least until the Hirnantian (Pothieret al 2015) The Irish Southern Uplands andBellewstown terranes amalgamated with the north-ern and northeastern margin of the Leinster Ter-rane respectively in the Llandovery to Wenlockduring the Salinic Orogeny (450 423 Ma) in turnfollowed by amalgamation of the Irish MidlandValley and Grampian terranes (Murphy et al1991)

The Tramore areaThe Tramore Limestone Formation was deposited ina shallow to deep shelf environment on the south-eastern Leinster Terrane which deepened westwardsinto the local Leinster Basin (Fig 2) into which theDunabrattin Shale and Limestone formations weredeposited (Phillips et al 1976 Key et al 2005)Most of the sedimentary successions belonging tothe Duncannon Group represented a period of localrelative quiescence before the extensive volcanismwhich dominated the Caradoc volcanogenic Car-righalia and Campile formations (Bruck et al 1979Carlisle 1979 Key et al 2005) Most of the upperDarriwilian lower Sandbian Tramore LimestoneFormation was not directly affected by volcanicactivity except for the lower and upper parts of theformation The upper Darriwilian Dunabrattin ShaleFormation and the lower part of the lower SandbianDunabrattin Limestone Formation accumulated in avolcanically active area of the Leinster Basin Vol-canic activity in this area subsided during depositionof the upper part of the Dunabrattin Limestonebut commenced again and became widespread insoutheast Ireland during deposition of the middleSandbian lower Katian Carrighalia and Campileformations (Carlisle 1979 Harper amp Parkes 2000)The lower Katian (late Caradoc) Raheen contains anabundant deeper-water fauna dominated byOnniella and Sericoidea (Harper et al 2016) Thechemical composition of the Leinster volcanicsincluding basaltic andesitic and rhyolitic rocks sug-gests that the terrane was likely located in a transi-tional position between the Popelogan-Victoria arcand Tetagouche-Exploits backarc basin (Parkes1992 Tietzsch-Tyler amp Sleeman 1994)


Fig 2 Locality map A Ireland B Extent of the Duncannon Group (simplified from Key et al 2005) C Study area with fossil localities(simplified from Carlisle 1979) Shelf-basin facies boundary from Key et al (2005) Ps Pickardstown sections QS1 Quillia Section 1QS2 Quillia Section 2


MaterialThe brachiopod material described in the presentstudy was collected by Carlisle in the 1970s inan area 10 km SW of Waterford city extendingfrom Tramore in the east to Bunmahon in thewest The area is located on the southern marginof a belt of Lower Palaeozoic rocks which spanssoutheast Ireland (Fig 2) The brachiopods werecollected from the contemporary shallower-waterTramore and deep-water Dunabrattin Limestoneformations

Carlisle (1979) defined and described the strati-graphical units from which the genera were recordedbut most of the samples were not labelled accordingto locality formation and level within the strati-graphical column The present study used Carlislersquospersonal notes and her 1979 paper to organizethe brachiopod occurrences and arrived at threegroupings which define three separate palaeobio-geographical localities in the analyses TramoreLimestone shelf-facies brachiopods of late Darriwil-ian age (Units 1 2) Tramore Limestone shelf-faciesbrachiopods of early Sandbian age (Units 3 5 andthe barren Unit 6) and Dunabrattin Limestoneouter shelf to basin facies brachiopods of early Sand-bian age (Units I IV)

The collection is currently deposited at the Natu-ral History Museum of Denmark but will later betransferred to the Natural History Museum Lon-don During severe flooding in the museum andsubsequent relocation of the invertebrate collectionsa small number of the figured specimens were mis-laid These specimens are indicated on the platedescriptions and if they do come to light will beassigned NHM numbers and transferred to the col-lections in the Natural History Museum London

Stratigraphy and faunaThe Tramore and Dunabrattin Limestone forma-tions represent local sedimentary developments inthe lower parts of the lower middle Darriwilian tolower Katian Duncannon Group which comprises asuite of limestones black shales and basaltic andesi-tic and rhyolitic arc volcanics Both formations aredominated by calcareous clastic sediments interbed-ded with rhythmically developed massive to nodularlimestone bands Their stratigraphical relationshipsto other Duncannon Group formations within andnear the study area are shown in Figure 3

The Duncannon Group occurs in a band trendingnortheastwards from Dungarvan County Water-ford towards the south County Wicklow (Key et al

2005) (Fig 2B) The successions cropping out inthe study area (Fig 2C) are dominated by thesouthern development of the Duncannon Groupcomprising a variety of volcanic and volcaniclasticfacies (Harper amp Parkes 2000) Harper amp Parkes(2000) noted that the volcanogenic BunmahonFormation in the western part of the study areapossibly correlates with the Dunabrattin Shale aswell as the lower part of the Tramore LimestoneFormation which is supported by this study TheTramore Limestone Formation and the contempo-rary Bunmahon and Tramore Shale formationsform the oldest parts of the Duncannon Groupreaching into the Abereiddian Stage of the LlanvirnSeries (Fig 3) Many local stratigraphies have beendescribed in the Geological Survey of Irelandrsquos1100 000 map compilations for the region (egMcConnell et al 1994 Tietzsch-Tyler amp Sleeman1994 Sleeman amp McConnell 1995)

The age of the various formations belonging tothe Duncannon Group is constrained by microfos-sils graptolites brachiopods and trilobites (see Har-per amp Parkes 2000) These authors also discussedstratigraphy and correlation of the formations

Age of the Tramore Limestone FormationPrevious studies have assigned the Tramore Lime-stone Formation to the lower Sandbian based onshelly faunas (Williams 1976 Brenchley et al 1977Carlisle 1979 Parkes 1994) as well as to the late midDarriwilian based on conodonts representing theEoplacognathus lindstroemi Subzone of the Pygodusserra Zone (Bergstrom amp Orchard 1985) In a revi-sion of Ordovician chronostratigraphy by Forteyet al (1995) the formation was suggested as rangingin age from the latest Darriwilian to the early Sand-bian (Llandeilian Aurelucian) This was also appliedby Owen amp Parkes (2000) following Bergstrom ampOrchard (1985) Further refinements tabulated inHarper amp Parkes (2000) indicated that the formationranges in age from the upper part of the upper Dar-riwilian murchisoni Zone to the lower Sandbian gra-cilis Zone Within the Tramore LimestoneFormation the Darriwilian Sandbian boundary islikely located between lithological Units 2 and 3 orin the lowermost part of Unit 3 This has not beenconfirmed by graptolite or conodont biostratigraphybut Carlisle (1979) recorded a brachiopod faunasimilar to that in Unit 3 of the Tramore LimestoneFormation immediately above the lower boundaryof the Dunabrattin Limestone Formation which wascorrelated by Harper amp Parkes (2000) with the Dar-riwilian Sandbian boundary Hence this studyplaces the Darriwilian Sandbian boundary at the


boundary between lithological Units 2 and 3 withinthe Tramore Limestone Formation The TramoreLimestone is overlain by the thin middle SandbianCarrighalia Formation which is in turn overlain bythe middle Sandbian lowermost Katian CampileFormation (Stillman 1978 Carlisle 1979 Harper ampParkes 2000)

Tramore and DunabrattinBunmahonsectionsThe Tramore Limestone Formation crops outbetween Tramore Bay in the east and BallydowaneBay in the west approximately 85 km west of Bun-mahon town (Key et al 2005) (Fig 2) The expo-sures are excellent along the 30- to 60-m-high seacliffs although they are only accessible by trenchedgullies (Wyse Jackson et al 2001 Key et al 2005)The Tramore Limestone grades from a shallowershelf facies in the east to a deeper basinal facies theDunabrattin Limestone Formation in the west withmaximum thicknesses of 65 and 450 m respectively

(Carlisle 1979 Harper amp Parkes 2000 Key et al2005) The transition from shelf to basinal faciesoccurs between Black Rock and Dunabrattin Head(Key et al 2005) (Fig 2)

The stratigraphy of the Tramore Limestone For-mation and its basinal correlatives was described andmeasured by Carlisle (1979) from the type sectionsand other exposures The Tramore Limestone is pri-marily described from its type section in the BarrelStrand area the Dunabrattin Limestone from itstype section at Dunabrattin Head and the Dunabrat-tin Shale Formation from its type section along1500 m of the foreshore east of Dunabrattin Headand from other sections near Bunmahon town(Fig 2) The measured sections are shown on thelogs in Figure 4 Brachiopods were collected at thefossil localities shown in Figure 2

Carlisle (1979) divided the Tramore LimestoneFormation into informal units and fauna associa-tions and correlated the Tramore Limestone withthe Dunabrattin Bunmahon stratigraphy based onfauna associations This correlation is mainly

Fig 3 Correlation chart showing formations of the Duncannon Group including the Tramore Limestone Formation and its correlativesfor selected outcrop areas in southeast Ireland Chronostratigraphy global stages British series and stages and graptolite zonation areredrawn from Cooper amp Sadler (2012) time-slices are redrawn from Webby et al (2004) and stratigraphical sections their biostrati-graphical correlation and fossil content are redrawn from Harper amp Parkes (2000) Abbreviations D Diplograptus Dicellogr Dicel-lograptus Dicranogr Dicranograptus St Streffordian


Fig 4 Sedimentary logs modified from Carlisle (1979) GZ British graptolite zonation (after Harper amp Parkes 2000) SL Sea-levelchanges correlated with the likely global events interpreted for Baltica by Nielsen (2004) Evae Evae Drowning Event Arn ArnestadDrowning Event U units FA fauna association (reinterpreted from Carlisle 1979) Fm formation Species common in the given faunaassociation of the Tramore Limestone Graptolites C vari Corymbograptus varicosus D mur Didymograptus murchisoni H teretiuscu-lus Hustedograptus teretiusculus D fol Diplograptus foliaceous Formations Tr Shale Fm Tramore Shale Formation Carrigh Fm Car-righalia Formation Bunm Fm Bunmahon Formation


followed in this study but supplemented by litholog-ical correlation and the graptolite zonation fromHarper amp Parkes (2000) therefore providing a dif-ferent correlation of the units than originally sug-gested by Carlisle (1979)

Tramore Shale Formation Tramore area

The Tramore Shale Formation is a local correla-tive of the upper part of the mainly LowerOrdovician Ribband Group and it is separatedfrom the Tramore Limestone Formation by amarked disconformity (Harper amp Parkes 2000)Carlisle (1979) recorded exposures of the forma-tion from the east Tramore area the formationcomprises over 1300 m of highly deformed unfos-siliferous dark grey shale with subordinate greybrown siltstone and sandstone Massively beddedstrongly cleaved tuffaceous shale containingnumerous flattened lenticular lapilli crops out inthe region of Perryrsquos Bridge and represent the ear-liest volcanic activity in the area (Carlisle 1979)The top of the formation is eroded in this area(Carlisle 1979) and Harper amp Parkes (2000)described a package of slumped units between theTramore Shale and Limestone probably masking adisconformity The depositional disturbance wasconsidered by Sleeman amp McConnell (1995) tohave been caused by slumping alone and not rep-resenting a significant time period If the slumpedunits represent a major hiatus the time intervalbetween the two formations may represent up to12 Ma and range from the uppermost Corymbo-graptus varicosus Zone to the uppermost Didymo-graptus murchisoni Zone as inferred by Harper ampParkes (2000)

Tramore Limestone Formation type section atBarrel Strand Tramore area

The informal units of Carlisle (1979) are used hereThe units referred to as Unit 1 6 in ascendingorder are characterized by their lithology and faunaassociations (see Fig 4 and Table 1) and the unitboundaries are coincident with those of the faunaassociations

LithologyUnit 1 the lowermost unit is approximately 2 mthick and consists of slumped calcareous and tuffa-ceous sandstone with contorted siltstone ribs Shalepebbles up to 4 cm long are recorded from the lowerparts of the unit (Carlisle 1979) The upper bound-ary of Unit 1 is characterized by the transition froma gradational tuffaceous calcareous sandstone layer

to an impure limestone band followed by calcareoussandstone without tuff as well as a shift from FaunaAssociation A to B (Table 1)

Unit 2 is approximately 13 m thick and composedof calcareous sandstone in the lower part changing tocalcareous siltstone in the upper part Both sedimenttypes are interrupted by rhythmically occurringimpure limestone bands up to 20 cm thick formed byconcentrations of shelly fauna and comprising about35 of the unit thickness (Mitchell et al 1972 Car-lisle 1979) The lower boundary is defined at theboundary between the uppermost tuffaceous sand-stone of Unit 1 and the lowermost impure limestoneband of Unit 2 In the lower part of the unit somelimestone bands make up coquinas of disarticulatedColaptomena shells and a sample comprising acoquina of several layers of oriented Sowerbyella(Sowerbyella) valves in a calcareous siltstone was prob-ably collected from the upper part of this unit (see thesystematics section) The fauna is dominated by filterfeeders and includes only one common trilobite spe-cies Calyptaulax jamesii The fauna has been some-what exposed to sorting and reorientation of valvesbut is otherwise fairly well preserved The upperboundary of Unit 2 is characterized by the transitionfrom an impure limestone band to a gradational cal-careous siltstone layer followed by an impure lime-stone band and calcareous shale as well as a shift fromFauna Association B to C (Table 1)

Unit 3 is approximately 14 m thick and consistsof calcareous shale and siltstone Impure limestonebands up to 15 cm thick comprising about 25 ofthe unit thickness occur rhythmically (Mitchell et al1972 Carlisle 1979) The limestone bands make upcoquinas formed by shell beds in the lower part ofthe unit Upwards these bands become nodular andconcomitantly the content of the shelly fauna decli-nes (Carlisle 1979) The shelly fauna is fragmentedand sorted The upper boundary of Unit 3 is charac-terized by the gradational transition from calcareousshale to an impure nodular limestone band a littlemore than 1 m above a 3-m-thick horizon of domi-nantly calcareous siltstone as well as a shift fromFauna Association C to D (Table 1)

Unit 4 is approximately 10 m thick and consti-tutes a dark shale with rhythmically occurringimpure nodular limestone bands up to 10 cm thickwhich comprise up to 12 of the unit thickness(Mitchell et al 1972 Carlisle 1979) A sparse faunadominated by small trilobites is concentrated in thelimestone bands and the preservation of the shellyfauna is excellent (Carlisle 1979) The upper bound-ary of Unit 4 is characterized by the transition fromdominantly calcareous shale to dominantly calcare-ous siltstone The boundary is defined between an


Introduction 1Previous work 2Geological setting 3Tectonic history of Ganderia and Avalonia 4Th e Iapetus Ocean 5Ireland 6

Th e Leinster Terrane 7Docking history 7Th e Tramore area 7

Material 9Stratigraphy and fauna 9

Age of the Tramore Limestone Formation 9Tramore and DunabrattinBunmahon sections 10

Tramore Shale Formation ndash Tramore area 12Tramore Limestone Formation ndash type section at Barrel

Strand Tramore area 12Lithology 12Fauna associations 14

Tramore Limestone Formation ndash other sections 14Pickardstown sections (Ps) 14 Quillia Section 1 (QS1) 14Quillia Section 2 (QS2) 14

Bunmahon Formation ndash BunmahonDunabrattin area 15Dunabrattin Shale Formation ndash BunmahonDunabrattin

area 15Dunabrattin Limestone Formation ndash Bunmahon

Dunabrattin area 15Lithology and fauna 16

Correlation 16Depositional setting and ecology 17

Local events 17Tramore Limestone Formation 17Dunabrattin Limestone Formation 19

Palaeobiogeographical reconstructions 20New reconstructions for the Iapetus Ocean 22

Ganderian terrane positions 22Longitudinal separation 22Latitudinal drift of the Ganderian-Avalonian segment 22

Brachiopod provinces 24Faunal distribution 24Darriwilian provinces and faunas 26

Th e Low-latitude Province on the Laurentian Platform 26An early Scoto-Appalachian fauna 27Th e Toquima-Table Head province 28Th e mixed faunas of the Leinster Terrane and

East Avalonia 31Th e Leinster Terrane 31East Avalonia 32

Th e Celtic province 32Th e Baltic Province 34Th e High-latitude Province 35

Darriwilian faunal migration patterns implications on oceanic current confi guration 35Migrations from the Laurentian margins and

intraoceanic islands to the south IapetusndashTornquist region 38

Migrations within the south IapetusndashTornquist region 38Th e Rheic gyre and the High-latitude Province 40Th e Precordillera 40

Early Sandbian brachiopod provinces 41Th e Low-latitude Province on the Laurentian Platform 41Th e Scoto-Appalachian Province 42Th e Anglo-WelshndashBaltic Province 43

Th e Leinster Terrane 44East Avalonia and Anglesey 46Baltica 47

Th e High-latitude Province 48Th e Precordillera 48

Conclusions 48Systematic palaeontology 50

Abbreviations 50Repository 50

Statistical methods 50Allometric growth 50

Phylum Brachiopoda Dumeacuteril 1806 51Subphylum Rhynchonelliformea Williams Carlson

amp Brunton 1996 51Class Strophomenata Oumlpik 1934 51Order Strophomenida Oumlpik 1934 51Superfamily Strophomenoidea King 1846 51Family Strophomenidae King 1846 51Subfamily Strophomeninae King 1846 51

Genus Tetraphalerella Wang 1949 51Tetraphalerella sp 52

Subfamily Furcitellinae Williams 1965 53Genus Dactylogonia Ulrich amp Cooper 1942 53

Dactylogonia costellata n sp 53Family Rafi nesquinidae Schuchert 1893 55Subfamily Rafi nesquininae Schuchert 1893 55

Genus Colaptomena Cooper 1956 55Colaptomena auduni n sp 56Colaptomena pseudopecten (MrsquoCoy 1846) 57

Superfamily Plectambonitoidea Jones 1928 59Family Plectambonitidae Jones 1928 59Subfamily Taphrodontinae Cooper 1956 59

Genus Isophragma Cooper 1956 59Isophragma parallelum n sp 59

Family Leptellinidae Ulrich amp Cooper 1936 61Subfamily Leptellininae Ulrich amp Cooper 1936 61

Genus Leptellina Ulrich amp Cooper 1936 61Leptellina llandeiloensis (Davidson 1883) 61

Subfamily Palaeostrophomeninae Cocks amp Rong 1989 62Genus Glyptambonites Cooper 1956 62

Glyptambonites sp 62Family Grorudiidae Cocks amp Rong 1989 63

Genus Grorudia Spjeldnaeligs 1957 63Grorudia grorudi Spjeldnaeligs 1957 63

Family Leptestiidae Oumlpik 1933a emend Cocks amp Rong 1989 64Genus Leptestiina Oumlpik 1933a 64

Leptestiina derfelensis (Jones 1928) 65Family Sowerbyellidae Oumlpik 1930 66Subfamily Sowerbyellinae Oumlpik 1930 66

Genus Sowerbyella Jones 1928 66Subgenus Sowerbyella (Sowerbyella) Jones 1928 66

Sowerbyella (Sowerbyella) antiqua Jones 1928 66Order Billingsellida Schuchert 1893 70Suborder Clitambonitidina Oumlpik 1934 70Superfamily Clitambonitoidea Winchell amp Schuchert 1893 70Family Clitambonitidae Winchell amp Schuchert 1893 70

Genus Atelelasma Cooper 1956 70Atelelasma longisulcum n sp 70

Class Rhynchonellata Williams Carlson amp Brunton 1996 73Order Orthida Schuchert amp Cooper 1932 73Suborder Orthidina Schuchert amp Cooper 1932 73Superfamily Orthoidea Woodward 1852 73Family Orthidae Woodward 1852 73

Genus Sulevorthis Jaanusson amp Bassettt 1993 73Sulevorthis aff S blountensis (Cooper 1956) 73

Family Glyptorthidae Schuchert and Cooper 1931 74Genus Glyptorthis Foerste 1914 74

Glyptorthis crispa (MrsquoCoy 1846) 74Family Hesperorthidae Schuchert amp Cooper 1931 77

Genus Hesperorthis Schuchert amp Cooper 1931 77Hesperorthis leinsterensis n sp 77

Family Plaesiomyidae Schuchert 1913 86Subfamily Plaesiomyinae Schuchert 1913 86

Genus Valcourea Raymond 1911 86Valcourea confinis (Salter 1849) 86

Family Productorthidae Schuchert amp Cooper 1931 87Subfamily Productorthinae Schuchert amp Cooper 1931 87

Genus Productorthis Kozłowski 1927 87Productorthis sp 87

Superfamily Plectorthoidea Schuchert amp LeVene 1929 89

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Documents

Ordovician rhynchonelliformean brachiopods from Co ...€¦ · Ordovician rhynchonelliformean brachiopods from Co. Waterford, SE Ireland: Palaeobiogeography of the Leinster Terrane