Arenig (Middle Ordovician) ostracods from Baltoscandia: Fauna, assemblages and biofacies

alaeoecology 241 (2006) 492ndash514wwwelseviercomlocatepalaeo

Palaeogeography Palaeoclimatology P

Arenig (Middle Ordovician) ostracods from BaltoscandiaFauna assemblages and biofacies

Oive Tinn Totildenu Meidla Leho Ainsaar

Institute of Geology University of Tartu Vanemuise 46 Tartu 51014 Estonia

Received 27 October 2005 received in revised form 24 April 2006 accepted 2 May 2006

Abstract

The Arenig ostracod fauna of Baltoscandia is the oldest known and amongst the most thoroughly studied ostracod faunas in theworld The fauna is dominated by eridostracans and palaeocopes and comprises altogether about fifty species from sevensuborders The ten most abundant ostracod species make up 90 of the total Arenig fauna Overall ostracod diversity estimates inthe Arenig of the Baltoscandian Palaeobasin are low but show gradual increase in diversity at younger horizons Low diversitymay be due to unfavourable climate conditions in the Baltoscandian Palaeocontinent during the earlier Arenig and may also be dueto the early stage of evolution of ostracod faunas (ie pre their main diversification during the Llanvirn) Thirteen facies relatedArenig ostracod assemblages are distinguished in the Baltoscandian Palaeobasin In early- and mid-Volkhov time the assemblagesshow almost basinwide distribution suggesting many ostracod species were environmental generalists Major distinctions betweendifferent ostracod biofacies zones can be seen from the late Volkhov onwards when the differentiation of ostracod biofacies in thePalaeobasin marks the onset of major depth differences Ostracod assemblage-based reconstruction of sea-level changes in thestudied area agrees well with the sequence stratigraphic interpretation of the succession and with a sea level curve determined onthe basis of sedimentological datacopy 2006 Elsevier BV All rights reserved

Keywords Ordovician Arenig Baltoscandia Ostracods Palaeoecology Biofacies

1 Introduction

Ostracods are an important component of fossil as-semblages in theArenig ofBaltoscandia being also one ofthe oldest thoroughly studied ostracod faunas in theworldThe extensive data of the Arenig ostracods of Baltoscan-dia covers their taxonomy and stratigraphy at differentoutcrops and sections (Oumlpik 1935 1939 Hessland 1949Henningsmoen 1953ab 1954 Sarv 1959 1960 1963Schallreuter 1983 1988 1989 1993 Gailīte 1982a

Corresponding authorE-mail address oivetinnutee (O Tinn)

0031-0182$ - see front matter copy 2006 Elsevier BV All rights reserveddoi101016jpalaeo200605002

Sidaravičienė 1992 Vannier et al 1989 Potildeldvere et al1998 Melnikova 1999) The major objective of the pre-sent paper is to give a comprehensive taxonomic overviewof the early ostracod fauna and its diversity through theArenig of Baltoscandia

Fossil ostracods like modern species were probablyhighly sensitive to environmental conditions and are thusincreasingly used for palaeoecologic studies all over theworld (Boomer et al 2003) Systematic sampling forostracods in different parts of the Baltoscandian areaduring recent years has lead to several papers dealing withostracod facies analysis (Meidla et al 1998 Tinn andMeidla 1999 2001) However these papers have

493O Tinn et al Palaeogeography Palaeoclimatology Palaeoecology 241 (2006) 492ndash514

analysed ostracod faunas of single localities only withsome references to adjacent regions The second objectiveof this paper is to define ostracod assemblages by statis-tical methods and to demonstrate palaeoecological rela-tionships between Arenig ostracod taxa Numerousstudies have shown that the distribution of benthic ostra-cod assemblages can be controlled by several environ-mental and sedimentological parameters likewater depthsubstrate salinity temperature etc (Siveter 1984) De-tailed data on temporal and geographical distribution ofostracod assemblages are used for defining ostracod bio-facies in the Arenig Baltoscandian Palaeobasin bypresencendashabsence data and cluster analysis

2 Geological setting

Palaeomagnetic data and palaeontological evidence(Scotese and McKerrow 1990 Torsvik et al 1991Torsvik 1998 Cocks and Torsvik 2005) suggest that theBaltica palaeocontinent occupied temperate southernpalaeolatitudes (about 45ndash60deg) during the Early Ordovi-cian The Early and Middle Ordovician sediments ofBaltoscandia were deposited in a sediment-starved epi-continental sea with extremely flat sea bottom topogra-phy on a gently tilted ramp (Nestor and Einasto 1997)Low-rate deposition of carbonates replaced the siliciclas-tic-dominated sedimentation of the Baltoscandian epi-continental sea during latest Early Ordovician time TheMiddle Ordovician skeletal debris-rich carbonates withnumerous discontinuity surfaces are lacking in evidencefor tropical conditions (eg pelletal and oolitic depositscoralndashstromatoporoid reefs etc) and have been inter-

Fig 1 Schematic map of the study area Roman numerals mark OrdovicianBelt IImdashCentral Baltoscandian Confacies Belt IIImdash Scanian Confacies Bel(Hessland 1949) 2 mdash Haumlllekis 3 mdash Skelbro

preted as cool-water sediments (Jaanusson 1973 Lind-stroumlm 1984 Nestor and Einasto 1997)

The Ordovician strata of the Palaeobasin developed inan array of distinct facies belts characterized by specificsedimentological and palaeontological features (Maumlnnil1966 Jaanusson 1973 1976 1982) and maintaining afairly constant relative position within the depositionalarea through time Jaanusson (1976) termed this type ofcomposite facies unit ldquoconfacies beltrdquo and suggested thatthey reflect a broad ecologic zonation controlled byenvironmental factors that also influenced depositionalconditions (Jaanusson 1982) The confacies pattern ap-parently reflects a general depth zonation of the Palaeo-basin (Maumlnnil and Meidla 1994) The North EstonianConfacies Belt (Fig 1) is regarded as the marginal area ofthe epicontinental sea where micritic skeletal calcare-nites sometimes containing silt and goethite ooids abun-dant glauconite grains and numerous impregnatedhardgrounds indicate a middle to inner ramp zone nearthe fair-weather wave base (Maumlnnil 1966 Nestor andEinasto 1997 Meidla et al 1998)

Opinions vary with respect to the Central Baltoscan-dian Confacies Belt but it is generally thought to re-present outer ramp or basinal facies near stormwave baseHowever the red-coloured or variegated argillaceouslimestones and marls of this unit are considered to be ofshallow-water origin by Jaanusson (1982) and Nielsen(1995) who attribute the numerous unconformities toeither emergence of the basin due to repeated sea levelfluctuations or to submarine non-deposition In contrastLindstroumlm (1963 1971 1979 1984) has attributed theextremely low sedimentation rate to deep sea conditions

confacies belts (after Jaanusson 1976) I mdash North Estonian Confaciest Arabic numerals mark studied sections 1mdash Siljan composite section

494 O Tinn et al Palaeogeography Palaeoclimatology Palaeoecology 241 (2006) 492ndash514

where sedimentation was pelagic or neritic and all breakswere submarine The deposits of the outer ramp were 2 to10 times as thick as those in the coeval inner ramp (Nestorand Einasto 1997) A previous ostracod study demon-strated the highest diversity of mid-Arenigian benthicfaunal assemblages in Vaumlstergoumltland Sweden in sedi-ments which suggest a moderately deep shelf basin justbelow the lower boundary of the photic zone (Tinn andMeidla 2001)

3 Stratigraphy

The stratigraphic framework of the Tremadoc andArenig sediments of the Baltoscandian Palaeobasin usedfor the present study is presented in Fig 2 The oldestostracod material of Baltoscandia comes from the basalbeds of the Bjoslashrkaringsholmen Formation (of late Varanguage) in the Oslo Region Norway (Henningsmoen 1954Ebbestad 1999) In Estonia and Latvia the corres-ponding part of the sequence is largely in hiatus Its onlyequivalent is the terrigenous Varangu Formation innorthern and central Estonia which does not containostracods Ostracods are also typically absent from theoverlying sand- and siltstones of the Leetse Formationalthough the calcareous interbeds in the upper part of theFormation require further investigation The beginningof predominantly carbonate sedimentation in the areaduring the latest Billingen also marks the beginning of acontinuous ostracod faunal record The reason for ab-sence of ostracods from the earlier sediments is not clearyet but the generally poor record of carbonate fossils inthese layers may be taphonomic (Tinn 2002)

A remarkable sedimentary structure pervading thewhole area is the discontinuity surface with ldquoamphora-like boringsrdquo known as ldquoPuumlstakkihtrdquo in Estonian (Orviku1960) This marks the lower boundary of the VolkhovStage in the BalticndashLadoga Klint area This discontinuitysurface can be traced over vast areas in Baltoscandia mdashfrom Oumlland in the west to Russia in the east and fromDalarna (Sweden) in the north to Poland in the south(Ekdale and Bromley 2001) It occurs in the nearshoreareas of the shelf to outer ramp settings

The Volkhov Stage forms a lithologically distinctiveunit in the sections of the BalticndashLadoga Klint Bios-tratigraphically the Volkhov Stage is defined by the Me-gistaspis polyphemus M simon and M limbata trilobitebiozones (Maumlnnil 1966 Maumlnnil and Meidla 1994) thatroughly correspond to the currently used Saka Vaumlaumlna andLangevoja substages Analogously the Kunda Stage hasbeen subdivided into the Asaphus expansus A ranicepsandMegistaspis gigasndashM obtusicauda trilobite biozoneswhich are thought to correspond to theHunderumValaste

and Aluoja substages In northern Estonia the HunderumSubstage and a considerable part of the Langevoja Sub-stage are missing (Fig 2) (Lamansky 1905 Orviku1960 Maumlnnil and Meidla 1994) In Latvia the boundarybetween the Zebre and Kriukai formations was correlatedwith the lower boundary of the Volkhov Stage (Gailīte1982b) A complete overview on stratigraphy of theVolkhov and Kunda stages in Estonia is given by Meidla(1997)

In Vaumlstergoumltland Sweden the sequence of the Volk-hov andKunda stages is represented by amacroscopicallyuniform red-coloured wackestonendashpackstone succes-sion referred to as the Lanna and Holen limestonesThis succession is underlain by the Toslashyen Shale that insome localities of Sweden is partly equivalent to thelowermost part of the Lanna Limestone (Jaanusson1982) A light grey packstone layer at the base of theHolen Limestone known as Taumlljsten forms a marker bedwith its thickness varying from several decimetres to twometres in Vaumlstergoumltland Jaanusson (1982) and Zhang(1998) assigned the Taumlljsten layer to the lowermost part ofthe Kunda Stage and this is usually correlated with theŠakyna Formation in the Central East Baltic (Maumlnnil andMeidla 1994) According to Meidla (in Potildeldvere et al1998) the lower boundary of the Taumlljsten unit lies abovethis level Within the North Estonian Confacies Belt theequivalent of the Taumlljsten unit passes into the SillaoruFormation (Dronov et al 2000)

The dark thermally altered Komstad Limestone repre-sents the onlymajor limestone bed in the shale-dominatedOrdovician succession of Bornholm Island The rocksuccession here yields trilobites indicative of the Me-gistaspis polyphemusM simonM limbata and Asaphusexpansus biozones (Poulsen 1966 Nielsen 1995) andthus roughly corresponds to the whole Volkhov Stage andthe Hunderum Substage of the Kunda Stage The lowerboundary of the Komstad Limestone represents a majorunconformity above the Alum Shale Formation (ofVarangu Hunneberg and Billingen age) Another majorunconformity is developed over the top of the KomstadLimestone marking the base of the Dicellograptus Shale(and assignable to the middle and upper Kunda) (Nielsen1995)

4 Material

The thirteen sections (8 outcrops and 5 core sections)investigated are Skelbro Haumlllekis Vaumlike-Pakri HarkuNotildemmeveski Toila Saka and Lava outcrops Jurmala R-1 Tartu-453 Laeva-8 Vergale-50 and Kaugatuma-509core sections (Figs 1 and 3) Composite data from out-crops of the Siljan area (Hessland 1949) were also

Fig 2 Stratigraphic framework for the Upper Tremadoc and Arenig strata of the Baltoscandian Palaeobasin based on the correlation log (Maumlnnil and Meidla 1994) with details and updatedinformation from Meidla (1997) and Heinsalu and Viira (1997) correlations with North-Atlantic conodont biozones (from Loumlfgren 1995 2000) and Baltoscandian trilobite biozones (Nielsen 1995)Data for Vaumlstergoumltland from Jaanusson (1982) and Dronov et al (2000) Bornholm from Nielsen (1995) Oslo region from Ebbestad (1999) St Petersburg region from Tolmacheva (2001)

495OTinn

etal

Palaeogeography

Palaeoclim

atologyPalaeoecology

241(2006)

492ndash514


incorporated in this study The relevant data andreferences about the studied sections are presented inTable 1 The lithology and stratigraphy of the studiedsections as well as the sample positions are presented inFigs 2 and 3

286 samples were studied in total the number of sam-ples per rock section varies from 3 in the Skelbro sectionto 49 in the Lava section Due to limited thicknesses offossil-bearing layers the least sampled (14 samples) is theBillingen Stage The Volkhov Stage is represented bysome 176 samples and the Kunda Stage by 83 samplesThe number of specimens per sample varies from one to1620 the total number of specimens included in theanalysis is 39300

Most carbonate samples were processed with standardphysical disintegration methods which are comparable tonatural weathering The crushed limestone samplesweighing about 05 to 15 kg were disintegrated withsodium hyposulphite To obtain a satisfactory degree ofdestruction heating and cooling cycles were repeated upto 10 times for clay-rich marls andmore than 50 times forhard thermally-altered limestones The washed and driedmaterial was sieved into four fractions (N2 mm 05ndash2 mm 025ndash05 mm b025 mm) Ostracods were pickedfrom the two intermediate fractions using a stereoscopicbinocular microscope with the magnification at 16ndash25timesOstracod material from the clay layers in the Lava andNotildemmeveski sections was obtained by washing through025 mm sieves

Table 1Basic data and references for the studied sections

Section Country Type Stratigraphy No of samp(BIndashBIII)

Haumlllekis Sweden Quarry BII BIII 16 (0-7-9)Harku Estonia Trench section BI BII BIII 32 (1-30-1)

Jurmala Latvia Drillcore BIBII BIII 18 (1-14-3)

Kaugatuma Estonia Drillcore BI BII BIII 12 (1-9-2)

Laeva-8 Estonia Drillcore BIII 6 (0-0-6)

Lava Russia Natural cliff BI BII BIII 49 (7-41-1)

Notildemmeveski Estonia Natural cliff BI BII BIII 28 (1-23-3)Saka Estonia Trench section BI BII BIII 24 (0-23-1)Siljan Sweden Composite BIII 46 (0-0-46)Skelbro Denmark Quarry BII BIII 3 (0-2-1)Tartu Estonia Drillcore BII BIII 12 (0-5-7)

Toila Estonia Natural cliff BI BII 17 (1-16-0)VaumlikendashPakri Estonia Natural cliff BI BII BIII 23 (1-21-1)Vergale-50 Estonia Drillcore BII BIII 19 (0-9-10)

BI mdash Billingen Stage BII mdash Volkhov Stage BIII mdash Kunda Stage

The ostracod material studied is of variable preserva-tion (Table 1) Generally in the western and southern partof the study area the calcitic carapaces exhibit good pre-servation In several Estonian sections the carbonate faunaof the lower part of the Volkhov Stage has been damagedor destroyed by secondary dolomitization Occasionallydolomitization has affected ostracod carapaces also in theBillingen Stage of the Lava section

Multivariate statistical analyses were performed withstatistical software packages STATISTICA 61 and PASTthe latter being a special software package designed forpalaeontological data analysis (Hammer et al 2001) Thetotal number of species included in the analysis is 49representing 36 genera and 7 suborders The number ofspecies per sample varies from one to 15 in samples withrich and diverse ostracod faunas For statistical purposesthe data matrix was standardized by converting the countsof specimens in samples to a percentage of the entiresample Three measures of species diversity were calcu-lated (1) the ShannonndashWiener index whichmeasures theamount of uncertainty in the sample (Etter 1999) (2) thereciprocal diversity index of Simpson which is a measureof the probability that two organisms picked at randombelong to different species (Etter 1999) and (3) speciesrichness which is the total number of different species ineach sample The properties of the similarity coefficientshave been discussed by several authors (Shi 1993 Etter1999) Etter (1999) has emphasized that the ShannonndashWiener index is the most sensitive to changes in rare

les Heightdepth interval(m)

Preservationof ostracods

References

31 m Good Tinn and Meidla 20013 m Good Meidla et al 1998

Tinn and Meidla 2003483 m(8757hellip9240)

Good ndash

32 m(4621hellip4658)

Poorhellipgood ndash

14 m(298hellip2994)

Good ndash

8 m Good Tolmacheva andFedorov 2001

31 m Good ndash3 m Good Meidla et al 19984 m Poorhellipgood Hessland 19494 m Poor Tinn and Meidla 1999122 m(3696hellip3818)

Poor Potildeldvere et al 1998

27 m Good Dronov et al 200012 m Good Dronov et al 200012 m (952hellip9640) Good ndash

Fig 3 Stratigraphy and lithology of the studied sections Rectangles indicate ostracod samples white rectangles indicate empty samples


Fig 4 Tree diagram for 2286 cases clustered into 13 ostracod assemblages Unweighted pair-group average Euclidean distances 4 mdash O variabilisassemblage 7mdash T viridis assemblage 8mdash P procerus assemblage 11mdashU tolmachovae assemblage MIDDLE RAMP Billingen 13mdash L spinosaassemblage OUTERRAMPLowerVolkhov Strong dashed lines indicateArenig average values for ShannonndashWiener andSimpsons indices and richness



species whereas Simpsons index is more sensitive tochanges in common species For comparison the averageof the total count is given for each measure

The actual number of species recorded in the Arenig ofBaltoscandia is larger than used in the present analysis(Meidla et al 1998 Tinn and Meidla 2002 Tinn 2002)Some species were eliminated because of their scant re-cord However in some levelslocalities the ostracodassemblages were relatively poor but of rather specificcomposition To keep these specific localities included inthe data matrix several of such rare taxa (ldquoSilenisrdquo spMicrocheilinella sp U tolmachovae H proximus Ovariabilis) are still included The problem of selectivetreatment of outliersndash localities with very few taxa or taxawith very few occurrences ndash has been specifically dis-cussed by Shi (1993)

In order to group species with similar spatial andtemporal distribution patterns cluster analysis usingquantitative data was performed Euclidean distanceswere clustered with unweighted pair-group averagelinkage The analysis resulted in 13 clusters (Fig 4)treated here as ostracod assemblages For estimating thespecies mutual relationships Pearsons correlationmatrix (Table 2) was computed and Principal Compo-nent Analysis was performed

Ostracod assemblages were defined as consisting of(1) one dominant species showing strong prevalence inthe assemblage (Fig 5) (2) additional common speciesfrequent in the assemblage and closely related in thePearsons correlation matrix (Table 2) (3) occasionalspecies with significant positive values in the correla-tion matrix but present in occasional samples only

A specific problem concerns Conchoprimitia socialisThe species is widespread occurring through the Arenigall over the study area and has been documented in 83ofthe studied samples (Fig 6A) In comparison with theother Arenig ostracods the carapace ofC socialis is thickand several times larger than that of the other species Thiscould giveC socialis a higher fossilization (preservation)potential than the rest of the studied species with a smalland thin carapace artificially distorting the general pictureof ostracod assemblages Several samples contained spe-cimens of C socialis only while other ostracod specieswere either unidentifiable or destroyed by recrystalliza-tion The initial analysis (not presented here) of the datasetshowed about half of the studied samples belonging to theC socialis assemblage It is clear that C socialis was animportant component of ostracod assemblages but itsconsiderably higher preservation potential in comparisonwith the rest of the ostracod fauna would lead to inade-quate results in statistical analysis (some other attempts ofanalysis resulted in ldquobiofaciesrdquo distinguished mainly ac-

cording to the concentration ofC socialis) In order to geta more objective pictureC socialiswas omitted from theanalytical data matrix but data about the concentration ofthis species in samples of a particular biofacies are pre-sented below (compare also Shi 1993)

Specific problems related toC socialis suggest that thecomposition of the ostracod assemblages may be to someextent influenced by the changing duration of the labo-ratory treatment (different number of heating cycles due todifferent rock properties) This could result in a confusedpicture if the assemblages were distinguished mainlyaccording to different ratios of a small number of domi-nant species We still expect the treatment effects to beminor because of the fact that the assemblages are mostlyalso taxonomically distinct (being characterized by dis-tinct sets of dominant species) However we have toadmit that testing this assumption experimentally wouldbe extremely difficult because of the similar chemicalcomposition of the fossils and rock matrix which makesmore reliable quantitative methods unusable

5 Arenig ostracod fauna

The Arenig ostracod fauna (Fig 6) is dominated by aneridostracan species Conchoprimitia socialis that waspresent in 83 of studied samples and constitutes about30 of the total number of specimens This species istentatively considered to contain all the variety of Are-nigian species of Conchoprimitia distinguished in dif-ferent parts of Baltoscandia by several authors duringmore than a century (results of a special study are sub-mitted) The majority of other abundant species (Fig 6)comprise palaeocopes such as Ogmoopsis bocki Breze-lina palmata Glossomorphites digitatus Rigidella mitisand Protallinnella grewingkii The only other non-pa-laeocope besides C socialis amongst the most abundantspecies is the eridostracan Incisua ventroincisurata oc-curring in 32 of samples and constituting about 13 ofthe studied specimens Of the 49 studied species the tenmost abundant make up 90 of the total Arenig fauna(Fig 6B) The other species are either rare occurring inminor quantities or restricted to certain stratigraphic le-velsbiofacies only

Comparison of ostracod faunas from the BillingenVolkhov and Kunda stages (Figs 7ndash9) shows an unevenpicture The relatively low number of samples from theBillingen Stage (Fig 9) shows C socialis and R mitis asthe most abundant species present in 91 and 28 samplesrespectively The most abundant species of the Volkhovstage (Fig 8) are C socialis Ogmoopsis bocki Incisuaventroincisurata Brezelina palmata Rigidella mitisTallinnellina primaria and Protallinnella grewingkii

Table 2Pearsons correlation matrix for 36 species

Csocialis

Obocki

Iventroincisurata

Bpalmata

Gdigitatus

Rmitis

Asimplex

Pgrewingkii

Tprimaria

Aacuta

Enonumbonatus

Upunctosulcata

Pprocerus

Lcurvata

Ocornuta

Eeffusus

Utolmachovae

C socialis 100O bocki minus003 100I ventroincisurata 029 minus004 100B palmata minus003 002 minus005 100G digitatus 017 minus006 009 minus007 100R mitis 021 013 023 006 001 100A simplex 007 minus005 000 minus004 004 minus010 100P grewingkii 027 024 016 001 019 023 003 100T primaria minus009 002 minus007 011 minus009 minus001 minus005 minus004 100A acuta 014 minus001 004 minus004 005 minus009 003 minus008 minus005 100E nonumbonatus 005 minus002 minus002 minus001 061 minus001 003 minus002 minus003 006 100U punctosulcata 018 000 003 007 033 041 minus002 012 007 minus005 021 100P procerus 006 minus002 minus007 minus003 010 minus009 015 minus 008 minus 004 059 002 minus008 100L curvata minus001 minus003 minus005 minus002 001 minus006 034 minus006 minus003 015 010 minus004 016 100O cornuta 002 minus001 minus005 minus002 minus002 minus006 004 minus006 minus003 031 minus002 minus005 041 039 100E effusus minus004 minus001 minus002 minus001 minus003 minus003 012 minus003 minus001 minus001 minus001 minus003 003 037 minus001 100U tolmachovae 004 minus002 minus003 minus002 minus004 minus004 minus002 minus004 minus002 minus002 minus001 minus003 minus002 minus001 minus001 minus001 100E cicatriosa 014 minus002 000 minus003 004 minus001 005 minus003 minus003 051 003 minus005 051 012 027 minus001 minus001H macroreticulata 001 minus001 minus002 minus001 005 minus003 001 minus003 minus002 026 019 minus001 008 060 minus001 000 minus001L decumana 003 minus002 minus004 minus002 minus002 minus006 005 minus006 minus003 024 minus002 minus004 042 032 093 006 minus001G grandispinosus minus001 minus002 004 minus001 minus002 minus004 014 minus002 minus002 001 minus001 minus002 002 038 000 099 minus001U irrete minus005 028 007 minus003 001 minus005 minus002 000 minus005 000 minus003 002 minus006 minus004 minus004 minus002 minus003L ansiensis 008 003 minus001 007 009 036 minus002 019 minus004 001 009 033 001 007 minus003 minus001 minus002T murus 031 minus001 000 minus002 000 minus003 minus001 015 minus002 minus002 minus001 minus005 minus002 minus002 minus002 minus001 minus001E sigma minus001 minus002 minus003 minus002 010 minus004 000 minus004 minus002 013 000 minus005 020 003 001 minus001 minus001O variabilis minus002 minus001 minus001 minus001 minus003 minus003 minus001 minus003 minus001 minus001 000 minus003 minus001 minus001 002 000 minus001Baltonotella 005 minus002 minus004 minus002 000 minus005 064 minus005 minus003 031 minus001 minus006 057 032 028 minus001 minus001H proximus 005 minus001 minus002 minus001 minus003 minus003 minus001 minus003 minus001 minus001 minus001 minus003 minus001 minus001 minus001 000 072E reticulogranulatus 005 minus001 minus005 minus003 002 minus007 033 minus005 minus003 042 000 minus005 061 014 013 minus001 minus002L spinosa minus005 minus002 minus003 minus001 minus004 minus004 minus002 minus004 minus002 minus002 minus001 minus004 minus002 minus001 minus001 minus001 minus001Silenis minus003 minus001 minus002 minus001 minus003 minus003 minus001 minus003 minus001 minus001 minus001 minus001 minus001 006 minus001 000 minus001E andersoni 006 000 minus003 minus001 004 minus003 003 minus004 minus002 046 001 minus004 076 minus001 012 000 minus001C levis minus001 minus002 003 minus001 minus003 minus004 055 minus004 minus002 minus001 002 minus004 010 024 minus001 minus001 minus001Microcheilinella minus003 minus001 minus002 minus001 minus003 minus003 minus001 minus003 minus001 minus001 minus001 minus001 minus001 006 minus001 000 minus001

Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma

Ovariabilis Baltonotella

Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella


Themost abundant species of the Kunda Stage (Fig 9) areC socialis I ventroincisurata Aulacopsis simplexGlossomorphites digitatus Asteusloffia acuta and Pinna-tulites procerus

A few species have been recorded throughout thestudied stratigraphical interval These long-rangingspecies are the eridostracans C socialis and I ventroin-cisurata the palaeocopes Ogmoopsis bocki and Protal-linnella grewingkii the kloedenellocope Unisulcopleurapunctosulcata and the binodicope Laterophoresansiensis

The composite data of Arenig ostracod assemblagesin the Baltoscandian Palaeobasin is presented in Table 3

6 Arenig ostracod biofacies in the BaltoscandianPalaeobasin

61 Distribution of ostracod assemblages in differentramp facies zones

An ostracod biofacies distribution model for theArenig of the Baltoscandian Palaeobasin is presented inFig 11 Three facies zonesndash inner middle and outer ramp

ndash are distinguished in the model In the studied stra-tigraphical interval shallow water inner ramp sedimentsare mostly lacking because of erosion The only intervalshowing nearshore sedimentation features is the bioclasticgrainstone with quartz sand of the Pakri Formation It isexposed in the uppermost part of the VaumlikendashPakri sectionin northern Estonia and is characterized by the highdiversity Ogmoopsis variabilis assemblage

The other northern Estonian sections mdash HarkuNotildemmeveski Saka Toila and most of the VaumlikendashPakriand Lava sections show similar alternations of Ogmoop-sis bocki and Brezelina palmata assemblages in the lowerpart of the Volkhov Stage and Incisua ventroincisurataand Glossomorphites digitatus in the upper Volkhov andlower Kunda stages These assemblages of the middleramp biofacies occur in packstonendashwackestone litholo-gies representing open marine storm-influenced environ-ments The Jurmala Skelbro Vergale Laeva Tartu Siljanand Haumlllekis sections preserve outer ramp biofacies TheTallinnellina viridis and Unisulcopleura tolmachovaeostracod assemblages have been documented in the Lavasection and the Lavatiella spinosa assemblage only in thelower Volkhov Stage of the Jurmala section Most of the

Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella

100012 100021 minus001 100

minus001 minus001 006 100minus004 minus002 minus004 003 100minus001 014 minus003 minus002 minus006 100minus001 minus001 minus001 000 minus003 minus002 100025 004 003 minus001 minus003 minus002 minus001 100

minus001 000 minus001 004 022 minus001 minus001 minus001 100055 minus001 023 000 minus002 minus002 minus001 005 004 100

minus001 000 minus001 minus001 minus002 minus001 minus001 minus001 000 minus001 100038 002 011 minus001 minus004 minus003 minus002 052 minus001 058 minus001 100

minus001 minus001 minus001 minus001 minus002 minus002 minus001 minus001 minus001 minus001 minus001 minus001 100minus001 000 minus001 minus001 minus002 minus001 minus001 minus001 000 minus001 000 minus001 minus001 100049 000 009 minus001 minus002 minus002 minus001 003 000 046 000 063 minus001 000 100002 minus001 minus001 000 minus002 minus002 minus001 003 minus001 054 minus001 026 minus001 minus001 minus001 100

minus001 000 minus001 minus001 minus002 minus001 minus001 minus001 000 minus001 000 minus001 minus001 100 000 minus001


lower and middle parts of the Volkhov Stage showalternations of the R mitis T primaria B palmata andObocki assemblages representing middle ramp biofaciesThe upper Volkhov and Kunda Stages are dominated bythe Glossomorphites digitatus assemblage These assem-blages are also related to wackestones and packstones

62 Temporal distribution of ostracod biofacies

Data about the Billingen Stage ostracod assemblagescomes mostly from the Lava section The lower BillingenStage is dominated by the low diversity Unisulcopleuratolmachovae assemblage whereas the middle and upperpart of the Billingen Stage show alternations of theOgmoopsis bocki and Tallinnellina viridis assemblagesIn the Billingen Stage of the Toila section the Rigidellamitis assemblage representing the middle ramp biofacieswas documented (Fig 10) An outer ramp ostracodbiofacies is unknown from the Billingen Stage

Low diversity assemblages dominate also in the lowerpart of the Volkhov Stage In the outer ramp zone the lowdiversity Lavatiella spinosa assemblage occurs (Fig 10)The middle part of the Volkhov Stage shows basin wide

distribution of the low diversity Rigidella mitis Tallin-nellina primaria Ogmoopsis bocki and Brezelina pal-mata assemblages (Fig 11)

The first high diversity assemblages appear in theBaltoscandian Palaeobasin during late Volkhovian timewhen the Glossomorphites digitatus assemblage wasdocumented in the outer ramp and the Incisua ventroin-cisurata assemblage in the inner ramp facies (Fig 11)Basically the same situation can be seen in the KundaStage with high diversity G digitatus assemblages in theouter ramp I ventroincisurata in the middle ramp andOvariabilis in the inner ramp facies zone

63 Spatial and temporal ostracod biofacies dynamicsduring the Arenigian

The general stratigraphic framework of the Arenigstrata in the Baltoscandian area (Fig 2) is used as a back-ground for analysing the spatialtemporal distribution ofostracod biofacies (Fig 11) In the studied area conodontdata is present for the Lava (Tolmacheva and Fedorov2001) Tartu (Potildeldvere et al 1998 Stouge 1998) andMaumlekalda sections (12 km NE from the Harku section

Fig 5 Species composition of the studied ostracod assemblages



Viira et al 2001) Trilobite data is available for theSkelbro section (Nielsen 1995) More detailed analysis isbased on 29 laterally traceable ldquoquarrymens bedsrdquo(Dronov et al 2000) Individual beds in the Upper-BillingenndashVolkhov stratigraphic interval differ in rocktype colour specific hardground surface morphologiesand trace fossils glauconite grains etc and can be tracedover a distance of 250 km from the easternmost sectionsof the BalticndashLadoga Klint up to the central-northern

Fig 6 Arenig ostracod fauna of Baltoscandia A mdash relative abundance of Aabundant ostracod species C mdash diversity measures for total Arenig Billingeerror

Estonia (Dronov et al 2000) These beds were identifiedas tempestites and thus can be used as a framework fordetailed event-stratigraphic correlation

The distribution of ostracod biofacies in Harku SakaToila and Lava sections against combined conodont andevent-stratigraphical correlation of the Saka Toila andLava sections is presented in Fig 12 The comparison ofbed-by-bed lithostratigraphical correlation of the SakaToila and Harku sections (Dronov et al 2000) with the

renig ostracod species B mdash cumulative percentages of the ten mostn Volkhov and Kunda Stage ostracod assemblages Bars indicate plusmn5

Fig7

Relativeabundanceof

BillingenStage

ostracodsBarsindicate

plusmn5

error


distribution of ostracod assemblages in the same sec-tions reveals a spatial biofacies shift The appearance ofthe mid-Volkhov B palmata assemblage in the Sakaand Toila sections is related to the same event-stratigraphic level However in the Lava section thisassemblage appears deeper in the section and theparticular event horizon marks the appearance of the Rmitis assemblage This discrepancy is proved also byconodont data The appearance of the B palmataassemblage in the Lava section coincides with the lowerboundary of the Microzarcodina parva conodontBiozone but in the Harku section the B palmataassemblage appears above the lower boundary of theMparva conodont Biozone

In the Saka and Toila sections the R mitisassemblage lies above the B palmata assemblage andcontemporaneous appearance of this assemblage in re-gard to event-stratigraphic framework is confirmed inboth sections (Fig 12) The same stratigraphic level inthe Lava section marks the appearance of a new Gdigitatus assemblage which in the Toila section ap-peared considerably later

Considering the boundaries of conodont biozones andevent-stratigraphic markers as time boundaries the earlierappearance of certain ostracod biofacies in the Lava sec-tion can be inferred According to the Arenig lithofacieszonation of the Baltoscandian Palaeobasin (Dronov et al2000) the Harku Saka and Toila sections lie in themiddleramp closer to the shore than the Lava section (Fig 1) andthis interpretation is also supported by the data on ostra-cod population age structure (Tinn and Meidla 2003) Itfollows therefore that the B palmata R mitis and Gdigitatus assemblages shifted landward in the course of atransgression in mid-Volkhov time

7 Discussion

71 Ostracod diversity changes

Calculated average and maximum values of ostracoddiversity for the Billingen Volkhov and Kunda stages arepresented in Fig 6C and for the studied ostracod as-semblages in Fig 4 The diversity measures range fromthe least possible (1 for Simpsons index and richness 0for ShannonndashWiener index) to the maximum ShannonndashWiener value 21 Simpsons diversity 70 and richness15 All calculated diversity measures (Fig 6C) show agradual increase through younger horizons the lowestbeing in the Billingen Stagewithmean species richness of26 and the highest in the Kunda Stagewith richness up to60 This reflects a continuous progressive diversificationin the studied interval Unfortunately we lack a similar

Fig 8 Volkhov Stage ostracods A mdash relative abundance of Volkhov Stage ostracod species B mdash cumulative percentages of ten most abundant Volkhov Stage ostracod species Bars indicate plusmn5error

505OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514

Fig 9 Kunda Stage ostracods Amdash relative abundance of Kunda Stage ostracod species B mdash cumulative percentages of ten most abundant Kunda Stage ostracod species Bars indicate plusmn5 error

506OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514

Table 3Ostracod assemblages of the Arenig Baltoscandian Palaeobasin

Assemblage name Common species Occasional species Diversity measures Distribution

ShannonndashWiener

Simpson Richness

Incisuaventroincisurata

G digitatusO bockiP grewingkii

R mitis T primariaA acuta T lanceolataT murus B palmataU punctosulcata U irreteE nonumbonatus

09 22 52 Volkhov Stage in northern Estoniaand Lava sections lower part ofthe Kunda Stage in the Siljan area

Protallinnellagrewingkii

G digitatusO bocki

B palmata R mitisT primaria L ansiensis

08 20 38 North Estonia and transitional areaof the Volkhov age

Glossomorphitesdigitatus

A simplexA acutaP grewingkiiE nonumbonatus

P procerus O cornuta 11 29 53 Volkhov and Kunda stages

Ogmoopsisvariabilis

I ventroincisurata U irrete G grandispinosusO terpylae T marchicaT rara O novum

13 22 11 Kunda Stage of theVaumlikendashPakri section

Ogmoopsis bocki Rigidella mitisProtallinnellagrewingkii

T primaria U irreteB palmata I ventroincisurataE cicatriosaU punctosulcata

08 20 41 Volkhov stage of theNorth Estonian sections

Rigidella mitis I ventroincisurata P grewingkii O bockiU punctosulcataL ansiensis T lanceolata

07 20 33 Lower part of the Volkhov Stage inNorth Estonia and in the Volkhov andKunda stages in the Haumlllekis section

Tallinnellinaviridis

D lautaT primariaE nonumbonatus

U punctosulcataU tolmachovae

06 17 32 Billingen and Volkhov stage of theLava section

Pinnatulitesprocerus

O cornutaE sigma

A simplex 08 19 30 Kunda age of the Tartu andSiljan sections

Brezelina palmata U punctosulcataT primariaR mitisgt

O bocki P grewingkii 07 16 43 Volkhov age and from the Siljancomposite section of the Kunda age

Unisulcopleuratolmachovae

H proximusT viridis

U punctosulcata 07 17 35 Billingen age of the Lava section

Tallinnellinaprimaria

R mitis T viridis U punctosulcata 04 14 24 Lower part of the Volkhov Stage innorthern Estonian sections as wellas in the Jurmala Tartu and Lava

Euprimites anisus A simplex ndash 02 11 20 Upper part of the Kunda Stage inthe Haumlllekis section

Lavatiellaspinosa

ndash ndash 0 1 1 Base of the Volkhov Stage at theJurmala section


detailed ostracod diversity analysis for the Arenig in otherpalaeobasins but LateOrdovician ostracods of theBaltos-candian Palaeobasin show continuation of the same trendOstracod samples with 15 to 20 species are common in theCaradoc but at certain levels the number of species canreach up to 25 or even 30 (Meidla 1996) In this contextthe ostracod fauna of the Arenig Palaeobaltic Basin maybe characterized as a low-diversity fauna

From the Tremadoc of Baltoscandia only one ostracodspecies ndash Nanopsis nanella (Moberg and Segerberg1906) ndash has been documented (Henningsmoen 1954)Similarly the Billingen and early Volkhov stages yield

low-diversity U tolmachovae and L spinosa assem-blages Higher ostracod diversity assemblages were re-corded in late Volkhov and early Kunda sediments Whilethe Arenig sediments have yielded about 50 species fromthe whole palaeobasin the number of species and sub-species documented from the Upper Ordovician of Es-tonia reaches nearly 360 (Meidla 1996)

The palaeogeographical reconstructions (Torsvik et al1996) show the Baltoscandian Palaeocontinent lying athigher southern palaeolatitudes during the Cambrian andEarly Ordovician According to the carbonate sedimen-tation type (Jaanusson 1973 Lindstroumlm 1984 Nestor

Fig 10 Position of ostracod assemblages in the studied sections


and Eeinasto 1997) the investigated faunal assemblagesfrom the Arenig of Baltoscandia represent faunas of acool-water sediment-starved shelf basin Nearly all

authors emphasize the particular importance of the rapidnorthward drift of Baltica (Vannier et al 1989 Torsvik etal 1996) which turned the climate in the Baltoscandian

Fig 11 Distribution of ostracod assemblages in the inner middle and outer ramp facies zones of the Arenig Baltoscandian Palaeocontinent


area gradually warmer and led to the appearance of baha-mitic sediments (Jaanusson 1973) first tabulates (Motildetus1997) rugosan corals (Kaljo 1997) and stromatoporoids(Nestor 1997) during the early Upper OrdovicianGradual increase of diversity in various shelly fossilgroups like that of trilobites (Adrain et al 2004) can beascribed to this amelioration of climate

In recent environments ostracod diversity changeshave a rough correlation with broad temperature zona-tion although this general pattern is modified by severalother factors Progressive diversification of ostracodsthroughout the Tremadoc and Arenig of Baltoscandia(see above) could have evolutionary reasons but furtherdiversity increase towards the Upper Ordovician (datafrom Meidla 1996 discussed above) is obvious andcould tentatively be ascribed to the same reason As thepalaeocontinent moved towards the Equator climaticconditions were gradually improving perhaps resultingin the highly diverse and abundant Late Ordovicianostracod fauna that appeared in the Caradoc (Meidla

1996) At the same time the diversity was increasingremarkably fast during the Early to early Middle Ordo-vician from one ostracod species in the Tremadoc up to50 species recorded in the Arenig (Tinn 2002 Tinn andMeidla 2004) It is obvious that the Tremadoc and Arenigwere periods of rapid evolution of the early ostracodfauna an early evolutionary stage of ostracods and theaforementioned growing diversity trend was not simplydue to the improvement of the climate related to thenorthward drift of the Baltica continent

Presumably ostracod faunas from once isolated con-tinents like Laurentia could also migrate to BalticaContraction of the Tornquist Sea and the Iapetus Oceanduring the Middle to Late Ordovician improved the linksbetween the isolated terranes (Schallreuter and Siveter1985 Williams et al 2003) Ostracod faunal links bet-ween the plates were firmly established in the latestMiddle Ordovician and increasingly so in the Late Ordo-vician As a result from all these processes the diversity ofostracods in the latest pre-Hirnantian was remarkably

Fig 12 Distribution of main ostracod biofacies in Harku Saka Toila and Lava sections Conodont data for the Lava section by Tolmacheva andFedorov (2001) for the Harku section correlated from the nearby Maumlekalda section by Viira et al (2001) Detailed bed-by-bed sedimentological andstratigraphical correlation from Dronov et al (2000)


higher in Baltoscandia than in any other region wherecomparative data are available (Avalonia Ibero-Armor-ica Kazakhstan)

72 Palaeoenvironmental conditions

The environmental preferences of Palaeozoic neriticostracods were primarily determined by water depth andresulting factors such as temperature salinity waterenergy level light conditions bottom sediment characteroxygenation etc (Siveter 1984) In the Arenig of Baltos-candia distinct ostracod biofacies demonstrate probablydepth-related distribution pattern as was shown for the

Upper Ordovician (Meidla 1996) Available evidencesuggests some influence of changing water energy level(Tinn andMeidla 2001) TheArenig ostracod assemblageand biofacies analysis presented here does not offer cluesto critical environmental factors but allows demonstrationof broad facies control general ecologic zonation mdash butonly from late Volkhov time onwards

The early to middle Volkhov age R mitis T pri-maria B palmata and O bocki assemblages occur insections representing both the middle and outer rampfacies zones At the same time the sediments (type ofsubstratum) of these zones were distinct grading frommid-ramp packstones into calcareous mudstones of the


outer ramp and a similar pattern generally persists forthe studied stratigraphic interval It could be sug-gested that depth differences between the palaeobasinfacies zones were less distinctive during early andmid-Volkhov time than later resulting in a remarkablywide facies distribution of early-middle Volkhovostracod assemblages The facies pattern changedduring Volkhov time upper Volkhov and Kundastages show clear differentiation of biofacies zonesThe outer ramp zone was inhabited by the G digitatusassemblage the middle ramp zone by the I ventroin-cisurata assemblage and the inner ramp by the Ovariabilis assemblage This kind of differentiationapparently suggests a growing biofacies gradient in thepalaeobasin restricting the distribution of the partic-ular ostracod assemblages

73 Sea level changes

Different methods for reconstruction of sea-levelchanges in the Arenig Baltoscandian Palaeobasin havebeen used by Nielsen (1995 2004) Dronov et al (2003)and Tolmacheva et al (2003) Reconstructions byNielsen (1995 2004) were based mainly on trilobitedata from the Scanian and Bornholm areas while thoseby Dronov et al (2003) were based on detailedsedimentological data from fairly complete sections inthe St Petersburg area Tolmacheva et al (2003) studiedthe species diversity and community richness of variousfossil groups mdash conodonts brachiopods ostracodsechinoderms etc also in the St Petersburg areaHowever in the latter work no correlation was foundbetween small-scale variability in the diversity estimatesand small-scale sea-level changes reconstructed for theeastern part of the basin

Sequence stratigraphic interpretations for Arenigstrata in Baltoscandia have been proposed by Dronovand others (Dronov and Holmer 1999 Dronov et al2003) According to this model the sediments of theBillingen Stage represent a highstand system tract ofthe Latorp sequence and sediments of both theVolkhov and Kunda stages comprise the separatedepositional sequences respectively The middle rampOgmoopsis bocki assemblage in the Lava sectionoccupies a time of late highstand conditions in arelatively shallow sea The regression event at theBillingenndashVolkhov boundary (LatorpVolkhov se-quence boundary by Dronov et al 2003 BasalWhiterock Lowstand by Nielsen 2004) is representedby a noteworthy discontinuity surface throughout theBaltoscandian region (Ekdale and Bromley 2001)The lower part of the Volkhov Stage is interpreted as

a shelf margin system tract by Dronov et al (2003)The transgression episode (transgressive surface) andthe subsequent deepening of the sea in mid-Volkhovtime (Dronov et al 2003) is tracked by the Bpalmata assemblage throughout the palaeobasinespecially in the northern Estonian sections

The sediments of the upper part of the Volkhov Stagerepresent a highstand system tract with gradual marineregression (Dronov et al 2003) The regression reachedits peak at the VolkhovKunda stage boundary interpretedas major sequence boundary (Dronov and Holmer 1999)In the westernmost part of the palaeobasin in the shale-dominated Bornholm and Scania areas the regression ledto the westward shift of the carbonate facies the KomstadLimestone (Nielsen 1995 2004) The inner-middle rampsections in northern and central Estonia on the other handshow a remarkable sedimentary gap at the VolkhovndashKunda boundary interval According to the present datathe sections in the St Petersburg region (eg Lava section)show almost continuous sedimentary transition from theVolkhov to the Kunda Stage During that regression eventand following the lowstand period of theKunda sequencethe outer ramp zone was inhabited by the G digitatusostracod assemblage and the middle ramp zone by the Iventroincisurata ostracod assemblage In the Siljan com-posite section the lowstand sediments are marked by theI ventoincisurata and B palmata assemblages in themiddle part of the Taumlljsten Layer which is a bioclasticpackstonendashgrainstone bed in between predominantlywackestone facies The position of the Siljan area in thegeneral depth zonation of the Baltoscandian basin hasbeen debated for several decades but the record of theseostracod assemblages here suggests that the area was lo-cated in deeper settings than the northern Estonian area(Tinn and Meidla 2001)

In general the ostracod assemblage-based recon-struction of sea-level changes in the studied area agreewith the Dronov et al (2003) sea level curve made onthe basis of sedimentological analysis of sections in theSt Petersburg region

8 Conclusions

1 The Arenig ostracod fauna of Baltoscandia com-prises about 50 ostracod species from sevensubordersmdash palaeocopes eridostracans kloedenel-locopes metacopes binodicopes spinigeritiidae andleiocopes The fauna is dominated by an eridostracanspecies Conchoprimitia socialis The palaeocopesOgmoopsis bocki Brezelina palmata Rigidellamitis Glossomorphites digitatus and Protallinnellagrewingkii are also very common The only other


non-palaeocope besides C socialis that is amongstthe most abundant species is the eridostracan Incisuaventroincisurata Although the number of studiedspecies is relatively high the ten most abundantostracod species make up 90 of the total Arenigfauna The remaining species are rare occur in minornumbers or are restricted to certain stratigraphiclevelsbiofacies Some of the ostracod species arerestricted to certain facies zones or have shortstratigraphical intervals There are also long-rangingspecies recorded throughout the Arenig (the eridos-tracans C socialis and I ventroincisurata thepalaeocopes O bocki and P grewingkii thekloedenellocope Unisulcopleura punctosulcata andbinodicope Laterophores ansiensis)

2 Arenig ostracod diversity estimates for the Baltos-candian Palaeobasin are consistently low with anaverage richness of 52 All calculated diversitymeasures show a gradual increase in diversity atyounger horizons diversity being lowest in theBillingen Stage with mean species richness of 26and highest in the Kunda Stage with mean richnessup to 60 The generally low number of taxa is due tothe early stage of evolution of the ostracod fauna inthe Arenig

3 Thirteen ostracod assemblages were distinguished inthe Baltoscandian Palaeobasin The G digitatus as-semblage is the most common of them constitutingabout 30 of the studied samples The next commonassemblages are those of O bocki and I ventroinci-surata Ostracod assemblages show almost basin-widedistribution during early and mid-Volkhov timeMajordistinctions between ostracod biofacies zones can beseen from the late Volkhov onwards when the outerrampwas inhabited by theG digitatus assemblage andthemiddle ramp by the I ventroincisurata assemblageDifferentiation of ostracod biofaciesmarks the onset ofmajor depth differences in the basin The ostracod as-semblage-based reconstruction of sea-level changes inthe studied area agrees with the sea level curve(Dronov et al 2003) and the sequence stratigraphicmodel (Dronov and Holmer 1999)

Acknowledgements

This study was supported by the Estonian ScienceFoundation grants No 4574 6207 and 6460 This paper isa contribution to the IGCP project 503 ldquoOrdovician Pa-laeogeography and Palaeoclimaterdquo and to the project0182531s03 supported by the Estonian Ministry of Edu-cation and Research The authors thank Mark Williamsand Jean Vannier for helpful reviews of the paper

Appendix A Supplementary data

Supplementary data associated with this article can befound in the online version at doi101016jpalaeo200605002

References

Adrain JM Edgecombe GD Fortey RA Hammer Oslash Laurie JRMcCormick T Owen AW Waisfield BG Webby BDWestrop SR Zhou Z-Y 2004 Trilobites In Webby BDParis F Droser ML Percival IG (Eds) The Great OrdovicianBiodiversification Event Columbia University Press New Yorkpp 231ndash254

Boomer I Horne DJ Slipper I 2003 The use of ostracods inpaleoenvironmental studies or what can you do with an ostracodshell Paleontological Society Papers 9 153ndash180

Cocks LRM Torsvik TH 2005 Baltica from the late Precambrianto mid-Palaeozoic times the gain and loss of a terranes identityEarth-Science Reviews 72 39ndash66

Dronov AV Holmer LE 1999 Depositional sequences in theOrdovician of Baltoscandia Acta Universitatis Carolinae Geolo-gica 43 133ndash136

Dronov AV Meidla T Ainsaar L Tinn O 2000 The Billingenand Volkhov stages in the northern East Baltic detailedstratigraphy and lithofacies zonation Proceedings of the EstonianAcademy of Sciences Geology 49 3ndash16

Dronov AV Koren TN Tolmacheva TYu Holmer L Meidla T2003 ldquoVolkhovianrdquo as a name for the third global stage of theOrdovician System In Albanesi GL Beresi MS Peralta SH(Eds) Ordovician from the Andes Instituto Superior de Correla-cion Geologica INSUGEO Tucuman Serie Correlacion Geolo-gica vol 17 pp 59ndash63

Ebbestad JOR 1999 Trilobites of the Tremadoc BjoslashrkaringsholmenFormation in the Oslo Region Norway Fossils and Strata 47(118 pp)

Ekdale AA Bromley RG 2001 Bioerosional innovation for livingin carbonate hardgrounds in the Early Ordovician of SwedenLethaia 34 1ndash12

Etter W 1999 Community analysis In Harper DAT (Ed) Nume-rical Palaeobiology John Wiley and Sons Chichester pp 285ndash360

Gailīte LK 1982a Ostrakody In Ulst RZh Gailīte LKYakovleva VI (Eds) Ordovik Latvii [Ordovician of Latvia]pp 114ndash132 (In Russian)

Gailīte LK 1982b Biostratigrafiya In Ulst RZh Gailīte LKYakovleva VI (Eds) Ordovik Latvii [Ordovician of Latvia]pp 169ndash223 (In Russian)

Hammer Oslash Harper DAT Ryan PD 2001 PAST PaleontologicalStatistics Software Package for Education and Data AnalysisPalaeontologia Electronica 4 1ndash9 (httppalaeo electronicaorg2001_1pastissue1_01htm)

Heinsalu H Viira V 1997 Varangu Stage In Raukas A TeedumaumleA (Eds) Geology and Mineral Resources of Estonia EstonianAcademy Publishers Tallinn p 58

Henningsmoen G 1953a Classification of Paleozoic straight hingedostracods Norsk Geologisk Tidsskrift 31 (185) 288

Henningsmoen G 1953b The Middle Ordovician of the Oslo RegionNorway 4 Ostracoda Norsk Geologisk Tidsskrift 32 35ndash56

Henningsmoen G 1954 Lower Ordovician Ostracods from the OsloRegion Norway Norsk Geologisk Tidsskrift 33 (41) 68


Hessland I 1949 Investigations of the Lower Ordovician of the SiljanDistrict Sweden I Lower Ordovician Ostracodes of the SiljanDistrict Bulletin of the Geological Institutions of the University ofUppsala 33 (97) 408

Jaanusson V 1973 Aspects of carbonate sedimentation in theOrdovician of Baltoscandia Lethaia 6 11ndash34

Jaanusson V 1976 Faunal dynamics in the Middle Ordovician (Viruan)of Balto-Scandia In Bassett MG (Ed) The Ordovician Systemproceedings of a Palaeontological Association symposium Birming-ham September 1974 University of Wales Press and NationalMuseum of Wales Cardiff pp 301ndash326

Jaanusson V 1982 Ordovician in Vaumlstergoumltland In Bruton DLWilliams SH (Eds) Field Excursion Guide IV InternationalSymposium of the Ordovician System Paleontological Contribu-tions from the University of Oslo vol 279 pp 164ndash183

Kaljo D 1997 Rugose corals In Raukas A Teedumaumle A (Eds)Geology and Mineral Resources of Estonia Estonian AcademyPublishers Tallinn pp 223ndash224

Lamansky VV 1905 Die aeltesten silurischen Schichten Russlands(Etage B) Trudy Geologicheskogo Komiteta N S St Peters-burg vol 20 pp 1ndash147

LindstroumlmM 1963 Sedimentary folds and development of limestonein an Early Ordovician sea Sedimentology 2 243ndash292

Lindstroumlm M 1971 Lower Ordovician conodonts of EuropaGeological Society of America Memoir Boulder Coloradovol 127 pp 21ndash61

Lindstroumlm M 1979 Diagenesis of Lower Ordovician hardgrounds inSweden Geologica et Palaeontologica 13 9ndash30

Lindstroumlm M 1984 The Ordovician climate based on the study ofcarbonate rocks In Bruton DL (Ed) Aspects of the OrdovicianSystem Palaeontological Contributions from the University ofOslo Universitetsforlaget Oslo vol 295 pp 81ndash88

Loumlfgren A 1995 The middle LannaVolkhov Stage (middle Arenig) ofSweden and its conodont fauna GeologicalMagazine 132 693ndash711

Loumlfgren A 2000 Early to early Middle Ordovician conodontbiostratigraphy of the Gillberga quarry northern Oumlland SwedenGFF 122 321ndash338

Maumlnnil R 1966 Istoriya razvitiya Baltiiskogo basseina v ordovike[Evolution of the Baltic Basin during the Ordovician] ValgusTallinn 200 pp (In Russian English summary)

Maumlnnil R Meidla T 1994 The Ordovician System of the EastEuropean Platform (Estonia Latvia Lithuania Byelorussia parts ofRussia the Ukraine and Moldova) In Webby BD Williams SH(Eds) The Ordovician System of the East European Platform andTuva (Southeastern Russia) IUGS Publication vol 28 pp 1ndash52 (A)

Meidla T 1996 Late Ordovician ostracodes of Estonia FossiliaBaltica vol 2 Tartu University Press 222 pp

Meidla T 1997 Volkhov Stage Kunda Stage In Raukas ATeedumaumle A (Eds) Geology and Mineral Resources of EstoniaEstonian Academy Publishers Tallinn pp 61ndash65

Meidla T Ainsaar L Tinn O 1998 Volkhov Stage in NorthEstonia and sea level changes Proceedings of the EstonianAcademy of Sciences Geology 47 (141) 157

Melnikova LM 1999 Ostracodes from the Billingen Horizon(Lower Ordovician) of the Leningrad Region PaleontologicalJournal 33 (147) 152

Moberg JC Segerberg CO 1906 Bidrag till kaumlnnedomen omCeratopygeregionen Meddelande fraringn Lunds Geologiska Faumlltk-lubb B Haringkan Ohlssons Boktryckeri Lund vol 2 16 pp

Motildetus M-A 1997 Tabulate corals In Raukas A Teedumaumle A(Eds) Geology and Mineral Resources of Estonia EstonianAcademy Publishers Tallinn pp 219ndash223

Nestor H 1997 Stromatoporoids In Raukas A Teedumaumle A(Eds) Geology and Mineral Resources of Estonia EstonianAcademy Publishers Tallinn pp 215ndash219

Nestor H Einasto R 1997 Ordovician and Silurian carbonatesedimentation basin In Raukas A Teedumaumle A (Eds) Geologyand Mineral Resources of Estonia Estonian Academy PublishersTallinn pp 192ndash204

Nielsen AT 1995 Trilobite systematics biostratigraphy andpalaeoecology of the Lower Ordovician Komstad Limestone andHuk Formations southern Scandinavia Fossils and Strata vol 38Scandinavian University Press Oslo pp 1ndash374

Nielsen AT 2004 Ordovician sea level changes a Baltoscandianperspective In Webby BD Paris F Droser ML Percival IG(Eds) The Great Ordovician Biodiversification Event ColumbiaUniversity Press New York pp 84ndash93

Oumlpik A 1935 Ostracoda from the lower Ordovician Megalaspis-limestone of Estonia and Russia Publications of the GeologicalInstitutions of the University of Tartu vol 44 12 pp

Oumlpik A 1939 Brachiopoden und Ostrakoden aus dem Expan-susschiefer Norwegens Norsk Geologisk Tidsskrift 19117ndash142

Orviku K 1960 O litostratigrafii volkhovskogo i kundaskogogorizontov v Rossii [About lithostratigraphy of the Volkhov andKunda stages in Russia] ENSV TA Geoloogia InstituudiUurimused 5 45ndash87 (In Russian German summary)

Potildeldvere A Meidla T Bauert G Stouge S 1998 Ordovician InMaumlnnik P (Ed) Tartu (453) Drillcore Estonian GeologicalSections vol 1 Geological Survey of Estonia Tallinn pp 11ndash17

Poulsen V 1966 CambrondashSilurian Stratigraphy of BornholmMeddelelser fra Dansk Geologisk Forening 16 117ndash137

Sarv L 1959 Ostrakody ordovika Estonskoj SSR [OrdovicianOstracodes in the Estonian SSR] ENSV Teaduste AkadeemiaGeoloogia Instituudi Uurimused 4 206 pp (In Russian Englishsummary)

Sarv L 1960 Stratigraficheskoe rasprostranenie ostrakod ordovikaEstonskoj SSR [Stratigraphical distribution of the Ordovicianostracodes from the Estonian SSR] ENSV TA GeoloogiaInstituudi Uurimused Tallinn 5 237ndash244 (In Russian)

Sarv L 1963 Novye ostrakody ordovika Pribaltiki [New ostracodesof the East Baltic] ENSV TA Geoloogia Instituudi UurimusedTallinn 13 161ndash188 (In Russian)

Schallreuter REL Siveter DJ 1985 Ostracodes across the IapetusOcean Palaeontology 28 577ndash598

Schallreuter R 1983 Glossomorphitinae und Sylthinae (Tetradelli-dae Palaeocopa Ostracoda) aus Backsteinkalk-geschieben (Mit-telordoviz) Norddeutschlands Palaeontographica A 180126ndash191

Schallreuter R 1988 Neue Muschelkrebse aus Geschieben Geschie-bekunde aktuell Mitteilungen der Gesellschaft fuumlr Geschiebe-kunde 4 101ndash103

Schallreuter R 1989 Ein Rogoumlsandstein-Geschiebe (Ordoviz) ausHamburg Archiv fuumlr Geschiebekunde Hamburg 1 9ndash30

Schallreuter R 1993 Ostrakoden aus ordovizischen Geschieben IIBeitraumlge zur Geschiebekunde Westfalens 2 Geologie undPalaumlontologie in Westfalen 27 (273 pp)

Scotese CR McKerrow WS 1990 Revised World maps andintroduction In McKerrowWS Scotese CR (Eds) PalaeozoicPalaeogeography and Biogeography Geological Society Memoirvol 12 pp 1ndash12

Shi GR 1993 Multivariate data analysis in palaeoecology andpalaeobiogeography mdash a review Palaeogeography Palaeoclima-tology Palaeoecology 105 199ndash234


Sidaravičienė TN 1992 Ostrakody Ordovika Litvy [Ordovicianostracodes of Lithuania] Vilnius 251 pp (In Russian)

Siveter D 1984 Habitats and mode of life of Silurian ostracodesSpecial Papers in Palaeontology 32 71ndash85

Stouge S 1998 Distribution of conodonts in the Tartu (453) core InMaumlnnik P (Ed) Tartu (453) drillcore Estonian geologicalsections 1 Appendix 13 Geological Survey of Estonia Tallinn

Tinn O 2002 Early Ostracode Evolution and PalaeoenvironmentalApplication in the Ordovician of Baltoscandia DissertationesGeologicae Universitatis Tartuensis 13 Tartu University Press145 pp

Tinn O Meidla T 1999 Ordovician ostracodes from the KomstadLimestone Bulletin of the Geological Society of Denmark 4625ndash30

Tinn O Meidla T 2001 Ordovician ostracodes from the Lanna andHolen Limestones Vaumlstergoumltland Sweden GFF 23 129ndash136

Tinn O Meidla T 2002 An enigmatic early palaeocope ostracodefrom the Arenig of NW Russia Acta Palaeontologica Polonica 47685ndash690

Tinn O Meidla T 2003 Ontogeny and thanatocoenosis of earlyMiddle Ordovician ostracode species Brezelina palmata (Krause1889) and Ogmoopsis bocki (Sarv 1959) Journal of Paleontology77 64ndash72

Tinn O Meidla T 2004 Phylogenetic relationships of the EarlyMiddle Ordovician ostracodes of Baltoscandia Palaeontology 47199ndash221

Tolmacheva T Ju 2001 Conodont biostratigraphy and diversity inthe Lower-Middle Ordovician of Eastern Baltoscandia (StPetersburg region Russia) and Kazakhstan Comprehensivesummary of doctoral dissertation Dept Earth Sci UppsalaUniversity 40 pp

Tolmacheva T Fedorov P 2001 The Ordovician BillingenVolkhovboundary interval (Arenig) at Lava River northwestern RussiaNorsk Geologisk Tidsskrift 81 161ndash168

Tolmacheva T Egerquist E Meidla T Tinn O Holmer L 2003Faunal composition and dynamics in unconsolidated sedimentsa case study from the Middle Ordovician of the East BalticGeological Magazine 140 31ndash44

Torsvik TH 1998 Palaeozoic palaeogeography a North Atlanticviewpoint GFF 120 109ndash118

Torsvik TH Ryan PD Trench A Harper DAT 1991 CambrondashOrdovician palaeogeography of Baltica Geology 19 7ndash10

Torsvik TH Smethurst MA Meert JG Van der Voo RMcKerrow WS Brasier MD Sturt BA Walderhaug HJ1996 Continental break-up and collision of Baltica and LaurentiaEarth-Science Reviews 40 229ndash258

Vannier JMC Siveter DJ Schallreuter REL 1989 Thecomposition and palaeogeographical significance of the Ordovi-cian ostracode faunas of Southern Britain Baltoscandia and Ibero-Armorica Palaeontology 32 163ndash222

Viira V Loumlfgren A Maumlgi S Wickstroumlm J 2001 An Early toMiddle Ordovician succession of conodont faunas at Maumlekaldanorthern Estonia Geological Magazine 138 699ndash718

Williams M Floyd JD Salas MJ Siveter DJ Stone P VannierJMC 2003 Patterns of ostracod migration for the ldquoNorthAtlanticrdquo region during the Ordovician Palaeogeography Palaeo-climatology Palaeoecology 195 193ndash228

Zhang J 1998 Middle Ordovician conodonts from the AtlanticFaunal Region and the evolution of key conodont generaMeddelanden fraringn Stockholms Universitets Institution foumlr Geologioch Geokemi 298 5ndash27


analysed ostracod faunas of single localities only withsome references to adjacent regions The second objectiveof this paper is to define ostracod assemblages by statis-tical methods and to demonstrate palaeoecological rela-tionships between Arenig ostracod taxa Numerousstudies have shown that the distribution of benthic ostra-cod assemblages can be controlled by several environ-mental and sedimentological parameters likewater depthsubstrate salinity temperature etc (Siveter 1984) De-tailed data on temporal and geographical distribution ofostracod assemblages are used for defining ostracod bio-facies in the Arenig Baltoscandian Palaeobasin bypresencendashabsence data and cluster analysis

2 Geological setting

Palaeomagnetic data and palaeontological evidence(Scotese and McKerrow 1990 Torsvik et al 1991Torsvik 1998 Cocks and Torsvik 2005) suggest that theBaltica palaeocontinent occupied temperate southernpalaeolatitudes (about 45ndash60deg) during the Early Ordovi-cian The Early and Middle Ordovician sediments ofBaltoscandia were deposited in a sediment-starved epi-continental sea with extremely flat sea bottom topogra-phy on a gently tilted ramp (Nestor and Einasto 1997)Low-rate deposition of carbonates replaced the siliciclas-tic-dominated sedimentation of the Baltoscandian epi-continental sea during latest Early Ordovician time TheMiddle Ordovician skeletal debris-rich carbonates withnumerous discontinuity surfaces are lacking in evidencefor tropical conditions (eg pelletal and oolitic depositscoralndashstromatoporoid reefs etc) and have been inter-

Fig 1 Schematic map of the study area Roman numerals mark OrdovicianBelt IImdashCentral Baltoscandian Confacies Belt IIImdash Scanian Confacies Bel(Hessland 1949) 2 mdash Haumlllekis 3 mdash Skelbro

preted as cool-water sediments (Jaanusson 1973 Lind-stroumlm 1984 Nestor and Einasto 1997)

The Ordovician strata of the Palaeobasin developed inan array of distinct facies belts characterized by specificsedimentological and palaeontological features (Maumlnnil1966 Jaanusson 1973 1976 1982) and maintaining afairly constant relative position within the depositionalarea through time Jaanusson (1976) termed this type ofcomposite facies unit ldquoconfacies beltrdquo and suggested thatthey reflect a broad ecologic zonation controlled byenvironmental factors that also influenced depositionalconditions (Jaanusson 1982) The confacies pattern ap-parently reflects a general depth zonation of the Palaeo-basin (Maumlnnil and Meidla 1994) The North EstonianConfacies Belt (Fig 1) is regarded as the marginal area ofthe epicontinental sea where micritic skeletal calcare-nites sometimes containing silt and goethite ooids abun-dant glauconite grains and numerous impregnatedhardgrounds indicate a middle to inner ramp zone nearthe fair-weather wave base (Maumlnnil 1966 Nestor andEinasto 1997 Meidla et al 1998)

Opinions vary with respect to the Central Baltoscan-dian Confacies Belt but it is generally thought to re-present outer ramp or basinal facies near stormwave baseHowever the red-coloured or variegated argillaceouslimestones and marls of this unit are considered to be ofshallow-water origin by Jaanusson (1982) and Nielsen(1995) who attribute the numerous unconformities toeither emergence of the basin due to repeated sea levelfluctuations or to submarine non-deposition In contrastLindstroumlm (1963 1971 1979 1984) has attributed theextremely low sedimentation rate to deep sea conditions

confacies belts (after Jaanusson 1976) I mdash North Estonian Confaciest Arabic numerals mark studied sections 1mdash Siljan composite section



3 Stratigraphy







4 Material



495OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



















References



Good ndash

32 m(4621hellip4658)


14 m(298hellip2994)

Good ndash





















Csocialis

Obocki

Iventroincisurata

Bpalmata

Gdigitatus

Rmitis

Asimplex

Pgrewingkii

Tprimaria

Aacuta

Enonumbonatus

Upunctosulcata

Pprocerus

Lcurvata

Ocornuta

Eeffusus

Utolmachovae


Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella










Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella

100012 100021 minus001 100























Fig7

Relativeabundanceof

BillingenStage


plusmn5

error





7 Discussion




505OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514


506OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



ShannonndashWiener

Simpson Richness






G digitatusO bocki






Ogmoopsisvariabilis













O cornutaE sigma





H proximusT viridis





Lavatiellaspinosa
































8 Conclusions






Acknowledgements




References















































































3 Stratigraphy







4 Material



495OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



















References



Good ndash

32 m(4621hellip4658)


14 m(298hellip2994)

Good ndash





















Csocialis

Obocki

Iventroincisurata

Bpalmata

Gdigitatus

Rmitis

Asimplex

Pgrewingkii

Tprimaria

Aacuta

Enonumbonatus

Upunctosulcata

Pprocerus

Lcurvata

Ocornuta

Eeffusus

Utolmachovae


Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella










Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella

100012 100021 minus001 100























Fig7

Relativeabundanceof

BillingenStage


plusmn5

error





7 Discussion




505OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514


506OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



ShannonndashWiener

Simpson Richness






G digitatusO bocki






Ogmoopsisvariabilis













O cornutaE sigma





H proximusT viridis





Lavatiellaspinosa
































8 Conclusions






Acknowledgements




References














































































495OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



















References



Good ndash

32 m(4621hellip4658)


14 m(298hellip2994)

Good ndash





















Csocialis

Obocki

Iventroincisurata

Bpalmata

Gdigitatus

Rmitis

Asimplex

Pgrewingkii

Tprimaria

Aacuta

Enonumbonatus

Upunctosulcata

Pprocerus

Lcurvata

Ocornuta

Eeffusus

Utolmachovae


Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella










Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella

100012 100021 minus001 100























Fig7

Relativeabundanceof

BillingenStage


plusmn5

error





7 Discussion




505OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514


506OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



ShannonndashWiener

Simpson Richness






G digitatusO bocki






Ogmoopsisvariabilis













O cornutaE sigma





H proximusT viridis





Lavatiellaspinosa
































8 Conclusions






Acknowledgements




References































































































References



Good ndash

32 m(4621hellip4658)


14 m(298hellip2994)

Good ndash





















Csocialis

Obocki

Iventroincisurata

Bpalmata

Gdigitatus

Rmitis

Asimplex

Pgrewingkii

Tprimaria

Aacuta

Enonumbonatus

Upunctosulcata

Pprocerus

Lcurvata

Ocornuta

Eeffusus

Utolmachovae


Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella










Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella

100012 100021 minus001 100























Fig7

Relativeabundanceof

BillingenStage


plusmn5

error





7 Discussion




505OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514


506OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



ShannonndashWiener

Simpson Richness






G digitatusO bocki






Ogmoopsisvariabilis













O cornutaE sigma





H proximusT viridis





Lavatiellaspinosa
































8 Conclusions






Acknowledgements




References





























































































Csocialis

Obocki

Iventroincisurata

Bpalmata

Gdigitatus

Rmitis

Asimplex

Pgrewingkii

Tprimaria

Aacuta

Enonumbonatus

Upunctosulcata

Pprocerus

Lcurvata

Ocornuta

Eeffusus

Utolmachovae


Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella










Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella

100012 100021 minus001 100























Fig7

Relativeabundanceof

BillingenStage


plusmn5

error





7 Discussion




505OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514


506OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



ShannonndashWiener

Simpson Richness






G digitatusO bocki






Ogmoopsisvariabilis













O cornutaE sigma





H proximusT viridis





Lavatiellaspinosa
































8 Conclusions






Acknowledgements




References













































































Ecicatriosa

Hmacroreticulata

Ldecumana

Ggrandispinosus

Uirrete

Lansiensis

Tmurus

Esigma


Hproximus

Ereticulogranulatus

Lspinosa Silenis

Eandersoni

Clevis

Microcheilinella

100012 100021 minus001 100























Fig7

Relativeabundanceof

BillingenStage


plusmn5

error





7 Discussion




505OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514


506OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



ShannonndashWiener

Simpson Richness






G digitatusO bocki






Ogmoopsisvariabilis













O cornutaE sigma





H proximusT viridis





Lavatiellaspinosa
































8 Conclusions






Acknowledgements




References





















































































Fig7

Relativeabundanceof

BillingenStage


plusmn5

error





7 Discussion




505OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514


506OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



ShannonndashWiener

Simpson Richness






G digitatusO bocki






Ogmoopsisvariabilis













O cornutaE sigma





H proximusT viridis





Lavatiellaspinosa
































8 Conclusions






Acknowledgements




References














































































505OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514


506OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



ShannonndashWiener

Simpson Richness






G digitatusO bocki






Ogmoopsisvariabilis













O cornutaE sigma





H proximusT viridis





Lavatiellaspinosa
































8 Conclusions






Acknowledgements




References














































































506OTinn

etal

Palaeogeography

Palaeoclim


241(2006)

492ndash514



ShannonndashWiener

Simpson Richness






G digitatusO bocki






Ogmoopsisvariabilis













O cornutaE sigma





H proximusT viridis





Lavatiellaspinosa
































8 Conclusions






Acknowledgements




References















































































ShannonndashWiener

Simpson Richness






G digitatusO bocki






Ogmoopsisvariabilis













O cornutaE sigma





H proximusT viridis





Lavatiellaspinosa
































8 Conclusions






Acknowledgements




References






































































































8 Conclusions






Acknowledgements




References

















































































Acknowledgements




References













































































Arenig (Middle Ordovician) ostracods from Baltoscandia: Fauna, assemblages and biofacies

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Transcript of Arenig (Middle Ordovician) ostracods from Baltoscandia: Fauna, assemblages and biofacies