Copyright © 1985 Ohio Acad. Sci. OO3O-O95O/85/OOO4-O175 $2.00/0

CHITINOZOANS FROM THE ORDOVICIAN-SILURIAN BOUNDARYBEDS IN THE EASTERN CINCINNATI REGION IN OHIO ANDKENTUCKY1

YNGVE GRAHN, Geological Survey of Sweden, Box 670, 75128 Uppsala, SwedenSTIG M. BERGSTROM, Department of Geology and Mineralogy, The Ohio State University, Columbus,

OH 43210

ABSTRACT. Representatives of seven species of chitinozoans, one of which is new(Ancyrochitina belfastensis n. sp.), were isolated from samples of the lowermost Silu-rian Belfast Member and of slightly younger beds of the Brassfield Formation and of theUpper Ordovician Preachersville Member of the Drakes Formation at two localities insouthern Ohio and north-central Kentucky in an attempt to determine the size of thestratigraphic gap at the Ordovician-Silurian paraconformity. Based on comparisons withsuccessions in Estonia and on Anticosti Island, Quebec, the chitinozoans suggest that thestratigraphic gap between the systems, which is likely to be due to a global sea level dropassociated with the Gondwana glaciation, represents an interval from the Ashgillian D.complanatus Zone to the early Llandoverian C. cyphus Zone and hence corresponds toabout four graptolite zones. The present study is the first record of Silurian chitinozoansfrom Ohio.

OHIOJ. SCI. 85 (4): 175-183, 1985

INTRODUCTIONThe outcrop area of richly fossiliferous

Ordovician rocks in southwestern Ohioand adjacent parts of Indiana and Ken-tucky, commonly referred to as the Cincin-nati Region, is the type area for the NorthAmerican reference standard of the UpperOrdovician, the Cincinnatian Series. Itsvaried faunas have been studied extensivelyfor more than 150 years, and most fossilgroups are now reasonably well known.However, a few groups are still littleinvestigated and one of these is the chit-inozoans, a group of organic-walled micro-fossils with enigmatic affinities. Despitethe fact that chitinozoans are commonthroughout the Cincinnatian succession,and have been shown to be excellent guidefossils elsewhere in the world, very littlehas been published on Cincinnatian chit-inozoans. Indeed, the available informa-tion includes only the description of two

'Manuscript received 15 April 1985 and in re-vised form 26 May 1985 (#85-11).

new species by Eisenack (1959) and a fewabstracts (Schopf and Schopf 1961, Miller1975, Bergstrom et al. 1981) along withtwo unpublished theses (Miller 1976,Knabe 1980). No chitinozoans have beenrecorded previously from Silurian rocks inOhio.

An interesting and important aspect ofthe geology of the Cincinnatian successionis its boundary relations to the overlyingSilurian rocks. Whereas there is a lithicallywell-marked unconformity at the systemicboundary in the western Cincinnati Re-gion (see, for instance, Rexroad et al.1965, Rexroad 1967) this boundary israther inconspicuous lithically on theeastern flank of the Cincinnati arch inHighland, Brown, and Adams counties inOhio and adjacent parts of Kentucky wherethe Ordovician-Silurian contact has beendescribed as conformable and gradationallocally (Peck 1966). Yet fossil evidenceindicates the presence of a significantstratigraphic hiatus in this area also,and the systemic boundary is apparentlya paraconformity.

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176 Y. GRAHN AND S. M. BERGSTROM Vol. 85

Despite several recent studies (Rexroadet al. 1965, Rexroad 1967, Rexroad inBerry and Boucot 1970, Gray and Boucot1972, Cooper 1975), there is considerableuncertainty about how much of the basalSilurian is missing. Further, there is noevidence of preservation of youngest Or-dovician (Hirnantian or Gamachian) rocksanywhere in the Cincinnati Region, and sothe gap at the systemic boundary is likelyinclude also the uppermost Ordovician.The purpose of the present study was todetermine if chitinozoans could clarify thecontroversial biostratigraphy at this sys-temic boundary.

STRATIGRAPHIC FRAMEWORKThe oldest Silurian unit in the study

area in Adams Co., Ohio, and Lewis Co.,Kentucky, (fig. 1) is the Brassfield For-mation, which contains fossils of early tomiddle Llandoverian (Early Silurian) age(Rexroad 1967, Berry and Boucot 1970,Cooper 1975, Rexroad and Kleffner 1984).The lowermost part of the Brassfield is alithically distinct unit of silty dolomiticlimestone and shale, up to 3 m thick, thatwas described as the Belfast Bed by Foerste(1896). This unit, now classified as amember of the Brassfield, crops out alongthe east-central flank of the Cincinnatiarch where it rests on Late Ordovicianrocks mapped as the Preachersville Mem-ber of the Drakes Formation (fig. 2).Rexroad (1967) reported abraded reworkedOrdovician conodonts from the lowermostBelfast at some localities, and Silurianones, including Icriodina (=Distomodus),throughout the unit. In his revision of theBrassfield conodonts, Cooper (1975) iden-tified Dtstomodus kentuckyemis, Icriodelladiscreta, and Ozarkodina hassi, amongothers, from the Belfast and referred it, aswell as the rest of the Brassfield, tp theD. kentuckyensis Zone. Cramer and Diez deCramer (1972) recognized acritarchs oftheir Veryhachium valiente -subfacies in theBelfast and suggested correlation of theunit with the upper part of the Corono-graptus cyphus Zone. Unfortunately, no

data supporting that biostratigraphic dat-ing are presented in their paper, and nograptolites are known from the Belfast.Although the Belfast has yielded no strati-graphically diagnostic megafossils, themicrofossil evidence just mentioned clearlysuggests an early Silurian, perhaps earlyLlandoverian, age.

Only relatively limited biostratigraphicinformation is available from the Preach-ersville Member of the Drakes Formation.Kohut and Sweet (1968) reported cono-donts from a locality close to ours in Ad-ams Co. According to a recent evaluationof these and other conodont data (Sweet1979, fig. 3), perhaps as much as half ofthe late Cincinnatian Richmondian Stageis missing in our study area, and this sug-gests the presence of a substantial hiatus inthe uppermost Ordovician.

METHODS AND MATERIALSSix samples from the Belfast, two samples from

the underlying Drakes, and two samples from thepost-Belfast Brassfield were investigated. Five sam-ples were collected from the well-known road cutsalong Ohio Route 41 S.W. of Ohio Brush Creek,Adams Co., Ohio, and five samples from a road cutE.N.E. of Tollesboro, Lewis Co., Kentucky (fig. 1).The samples, which had a weight of 0.1-0.4 kg,were treated following the laboratory methodsdescribed by Grahn (1980). Most of the samplesyielded very few chitinozoans (fig. 1). This is inagreement with the conditions in other areas wherethe relative abundance, as well as species diversity,of chitinozoans are low in the uppermost Ordovicianand lowermost Silurian. The Belfast samples yieldedfewer than 0.5 specimen per gram of rock except fora single sample from the Tollesboro section whichcontained 15.3 specimens per gram of rock. Thefrequency in the Preachersville was 0.09 and in thepost-Belfast Brassfield 0.44-1.9 specimens pergram of rock. All chitinozoans show some degree ofdistortion, probably caused by compaction of thesediment. Micrographs were taken of selected gold-coated specimens on a Cambridge S4-10 SEM at5 kV. All illustrated specimens are kept underOSU numbers in the type collection of the OrtonGeological Museum at The Ohio State University.

CHITINOZOAN BIOSTRATIGRAPHYDetailed evaluation of the biostrati-

graphic significance of the seven chit-inozoan species encountered is somewhathampered by the lack of useful information

OhioJ. Sci. ORDOVICIAN-SILURIAN CHITINOZOANS 177

Ohio BrushA Creek

Blue, Creek

125

FIGURE 1. Location of sections studied, stratigraphic level of each sample, and frequency of chitinozoans.The Ohio Brush Creek section (inset diagram A) is a high road cut along the west side of State Route 41at road curve with small intermittent stream forming a waterfall across the cliff face about 3.4 km(2.1 miles) N.E. of West Union and 9-8 km (6.1 miles) S. W. of the Ohio Brush Creek bridge, Adams Co.,Ohio. Sample A is from the top 10 cm of the Drakes; B, C, and D from basal 10 cm, 100 cm above thebase, and top 10 cm of the Belfast, respectively; and E from basal 10 cm of the post-Belfast Brassfield.Figures in boxes on vertical lines denote number of specimens of a particular species per gram of rock sample.The Tollesboro section (inset diagram B) is a road cut along Kentucky Highway 10 on hill S.W. of CabinCreek 4 km (2.5 miles) E. of junction with Kentucky Highway 57 in Tollesboro, Lewis Co., Kentucky. Thisis section 4A of Rexroad and Kleffner (1984). Sample F is from top 10 cm of the Drakes; G, H, and I fromB basal 10 cm, 42 cm above the base, and top 10 cm of the Belfast, respectively; and J from basal 10 cmof the post-Belfast Brassfield. Species designations in diagrams A and B are as follows: a, Ancyrochitina merga;b, Conochitina cf. C. iklaensis; c, Cyathochitina campanulaeformis; d, Conochitina sp.; e, Ancyrochitina sp.;f, A. cf. A. primitiva; g, A. belfastenis.

about the chitinozoan succession in theOrdovician-Silurian boundary interval inseveral key sequences in North Americaand abroad. However, such successionshave been documented from Sweden (Eise-

nack 1968, Grahn 1978), Estonia (Nestor1976, 1980, Nolvak 1980) and Podolia,USSR (Laufeld 1971), Belgium (Martin1973), and Anticosti Island, Quebec(Achab 1977b, 1981). Remarks on the dis-

OHIO

LEWIS CO.

178 Y. GRAHN AND S. M. BERGSTROM Vol. 85

SERIES

EAST-CENTRAL

KENTUCKY-S. OHIO

ANTICOSTIISLAND

CENTRALESTONIA

CONODONT ZONES

CINCINNATIARCH

GREATBRITAIN

GRAPTOLITE

ZONES

LLAN-

DOVER-

IAN

Noland Fm.

BrassfieldFm.

Gun River

Fm.

RaikkiilaFm.

Distomoduskentuckyensis

Becscie Fm.Belfast

Mbr.

SaardeFm.

Icriodelladiscrete

Icriodella

deflects

M. convolutus

C. gregarius

C. cyphus

Tamsalu Fm. vesiculosusVarbola Fm. A. acuminatus

KoigiMbr.

Ellis Bay

Fm.

Drakes Fm.

Amorpho -gnathus

ordovicicus

Amorpho -gnathus

ordovicicus

? persculptus

D. anceps

D.complanatus

FIGURE 2. Correlation of the Belfast and associated strata with units on Anticosti Island and in Estonia,and cosmopolitan conodont and graptolite zones.

tribution of our taxa are given in theAppendix, and here we summarize theirbiostratigraphic significance.

The chitinozoans from the Belfast do notshow any clear provincial affinity. Col-lectively, they confirm an Early Silurianage for the unit. The specimens herein re-ferred to as Conochitina cf. C. iklaensis arevery similar to, although not quite typicalof, representatives of the nominal speciesfrom the C. cyphus to M. convolutus zones inEstonia (Nestor 1980) and coeval strata inthe Gun River Formation of Anticosti Is-land (Achab 1981). We interpret the oc-currence of this form, which also is in thebasalmost Belfast, as indicating that thisunit in its entirety is probably not olderthan the C. cyphus Zone. Although notvery diagnostic biostratigraphically, theother chitinozoans present in the Belfastare in general agreement with this conclu-sion (see Appendix). Furthermore, a chit-inozoan species-assemblage typical of theC. gregarius Zone in Estonia appears in the

Brassfield somewhat above the Belfast(Grahn in prep.). Because there is no indi-cation of a stratigraphic break between theBelfast and the latter level, the appearanceof this assemblage may be viewed as addi-tional evidence of an early Llandoverian agefor the Belfast. This is in good agreementwith, and confirms, the dating of the unitby means of conodonts (Rexroad 1967,Cooper 1975, Rexroad and Kleffner 1984)and acritarchs (Cramer and Diez deCramer 1972).

The only species recovered from thePreachersville, Ancyrochitina merga, is pre-viously known from the Dicellograptuscompanatus Zone in the Sylvan Shale ofOklahoma (Jenkins 1970) and the VaurealFormation on Anticosti Island (Achab1977a) as well as coeval strata in theMaquoketa Shale of Kansas (Wright andMeyers 1981). Older occurrences arerecorded from the Maysvillian of Indianaand Ohio (Miller 1976) and Kentucky(Knabe 1980). The known range of this

OhioJ. Sci. ORDOVICIAN-SILURIAN CHITINOZOANS 179

species suggests that the uppermostPreachersville is not younger than theD. complanatus Zone, that is, the middleAshgillian. This is in agreement with datafrom megafossils and conodonts that sug-gest that late Ashgillian strata are missingin the entire Cincinnati Region.

Accordingly, as summarized in fig. 2,we conclude that in our study area thestratigraphic gap of the Ordovician-Silurian paraconformity corresponds to theupper Ashgillian (Hirnantian or Gam-achian stages) as well as an interval of threegraptolite zones in the lowermost Llando-verian. Although this is a significant hia-tus, the corresponding one on the westernflank of the Cincinnati arch may be evenlarger (Rexroad and Kleffner 1984).

REMARKS ON PALEOECOLOGYThe Ordovician-Silurian systemic

boundary break in the Cincinnati Regionhas a counterpart in many cratonic succes-sions around the world and is likely to bedue to a eustatic sea level drop, perhaps asmuch as 100 m., which was caused by theGondwana glaciation (Brenchley andNewall 1984). The Belfast was depositedduring the transgression following thislarge-scale regression.'At our Ohio BrushCreek locality, the interval of the systemiccontact is beautifully exposed for consid-erable distances in several long road cuts.In view of the fact that the stratigraphicgap may represent a time interval of severalmillion years, it is remarkable that thecontact is not marked by a conglomerate,channelled surface, or other lithic evidenceof erosional activity. The Preachersvilleand the Belfast appear to be perfectly con-formable; indeed, even at very close in-spection, it is locally not easy to pinpointthe precise level of the paraconformitywithin a few cm thick interval that hasbeen described as lithically transitional(Peck 1966). This masking of the contactis possibly due to reworking of argillaceousmaterial from the Preachersville into thebasalmost Belfast. This possibility is sup-ported by the fact that reworked Ordo-

vician conodonts are present locally in thelowermost Belfast (Rexroad 1967).

Although the position of the Belfast im-mediately above a major stratigraphicbreak suggests that the unit was laid downin shallow water, the precise water depthin the depositional environment is uncer-tain. No mudcracks, stromatolites, flat-pebble conglomerates, or other structuressuggesting very shallow water have beenreported from the Belfast, but the absenceof a varied megafossil fauna may be takenas an indication of restricted and perhapsstressed conditions. Gray and Boucot(1972) found spore tetrads to dominateamong the organic-walled microfossils inthe upper Preachersville and lower Belfastwhereas acanthomorphic acritarchs occurcommonly in the upper Belfast indicatingan increase in water depth during deposi-tion of the unit. In all likelihood the Cin-cinnati Region was above sea level duringlatest Ordovician and earliest Siluriantime, and non-marine conditions prevailedduring Belfast time in the Appalachian re-gion to the southeast of the study area. Yetthe presence of Silurian conodonts, acrit-archs, and chitinozoans throughout theBelfast proves the marine nature of the en-tire unit. Right above the Belfast, theBrassfield contains brachiopods of theCryptothyrella or Platymerella Communities{Eocoelia or Pentamerus) Benthic MarineLife Zones (Gray and Boucot 1972) alongwith a diversified fauna of other shallow-water organisms indicating the existence ofshallow-water marine conditions (Gordonand Ettensohn 1984). Chitinozoans areknown to be scarce, or absent, in rocksdeposited in very shallow water, especiallyunder intertidal or supratidal conditions(Laufeld 1974, Grahn 1981, 1982, Grahnand Bergstrom 1984). Their presencethroughout the Belfast, albeit in low num-bers in most samples, suggests depositionin a subtidal environment. Alternatively,these fossils, along with conodonts andacritarchs, might have been transported bycurrents from the normal life environmentof the organisms and deposited in very

180 Y. GRAHN AND S. M. BERGSTROM Vol. 85

shallow and possibly intertidal watersalthough, as noted above, lithic evidenceof intertidal or supratidal deposition hasnot been found. Our chitinozoan assem-blages are strongly dominated (99%) byrepresentatives of Ancyrochitina with longhollow appendices. It has been suggestedthat such appendices served as floating de-vices and that these forms were planktic(Laufeld 1967, Chaiffetz 1972, Grahn1978). If this interpretation is correct, it isobvious that such chitinozoans could betransported relatively easily from thenormal life environment of the chitino-zoophorans into more specialized environ-ments such as that in which the Belfast wasdeposited. Unfortunately, the conodontsrecorded from the Belfast are widespread inrocks representing a variety of shallow-water environments and their paleo-ecologic significance is uncertain. Gordonand Ettensohn (1984) suggested that theBelfast was deposited in a low-energylagoonal environment but additional sedi-mentologic study of the unit throughoutits area of occurrence, particularly in Ohio,is likely to add the data needed for adetailed assessment of its depositionalenvironment.ACKNOWLEDGMENTS. We are indebted to WalterC. Sweet, Sven Laufeld, Merrell Miller, and Carl B.Rexroad for constructive criticism of our manu-script, and to Helen Jones, Anthony J. Leonardi,and Karen Tyler for technical assistance. The seniorauthor is grateful for a post-doctoral fellowshipawarded him by The Ohio State University for the1983-84 academic year, which made it possible forhim to do cooperative research on North Americanchitinozoans. The Department of Geology and Min-eralogy at The Ohio State University provided fundsfor the SEM work and other expenses connected withthe present research.

APPENDIXREMARKS ON TAXONOMY

Brief comments on the chitinozoan taxa found aregiven below but to conserve space, we have omittedlists of synonyms and extensive descriptions. All thetaxa discussed are illustrated in fig. 3-15.

Ancyrochitina belfastensis n. sp. (fig. 3-5)HOLOTYPE: OSU 38451.ETYMOLOGY: Named for the Belfast Member, thetype stratum.

TYPE LOCALITY: Tollesboro section (see fig. 1 forlocation), 1.1 m above base of the Belfast.DESCRIPTION: An Ancyrochitina species with a cylin-drical neck half as long as the total vesicle length,and a subconical body with a convex base. Therounded basal edge carries about six appendiceswith their bases divided into two parts. The vesiclewall is smooth orad of the basal edge.DIMENSIONS: Total length 100-188 /u,m; max. width75-88 [Am; width of aperture 31-43 fim; max.length of appendices 31 fun.REMARKS: The branching of the appendices in thepresent species is similar to that in A. spongiosaAchab 1977, but our species is distinguished by hav-ing much more slender appendices that do not havethe spongy structure present in those of A.spongiosa. Furthermore, the latter species has five to10 appendices.KNOWN OCCURRENCE: The Belfast Member (earlyLlandoverian), Tollesboro, Kentucky. MATERIAL: 16specimens.

Ancyrochitina merga Jenkins 1970 (fig. 8-9)This species, the only chitinozoan recovered from

the uppermost part of the Preachersville, has a smallfungiform vesicle with almost straight flanks thattaper in a gentle curve into a neck that widens at theaperture. Most of the appendices are broken, butthose present are bifurcate. The vesicle wall issmooth or covered with very small spines. Jenkins(1970) recorded this form as common in the upperpart of the lower Sylvan Shale of Oklahoma (D.complanatus Zone), and it has also been reported fromcoeval strata in the Vaureal Formation on AnticostiIsland (Achab 1977a) and the Maquoketa Shale ofKansas (Wright and Meyers 1981). Other occur-rences include the Maysvillian of Indiana and Ohio(Miller 1976) and Kentucky (Knabe 1980).Ancyrochitina cf. A. primitiva Eisenack 1964

(fig. 6-7)At the Ohio Brush Creek section, specimens of

this species appear in the middle Brassfield wherethey dominate the chitinozoan fauna. In the Tolles-boro section it has been recovered also in the Belfast.Our specimens differ from typical specimens of A.primitiva in having appendices that are curved abor-ally. No ornamentation has been observed on theneck. Typical specimens of Eisenack's species arepresent in somewhat younger beds in southern Ohiothan those discussed here (Grahn, unpubl. data).Eisenack (1964) noted that this species exhibitsgreat intraspecific variation. The species is recordedfrom the upper Llandoverian to upper Ludlovian andis known from Baltoscandia (Eisenack 1964, 1968,1970, Laufeld 1974, Nestor 1982), Podolia, USSR(Laufeld 1971), Great Britain (Eisenack 1977), andPortugal (Paris 1981).

Ancyrochitina sp. (fig. 10)This species is sparingly represented in the Belfast

and in younger parts of the Brassfield. It has thecylindro-conical vesicle typical of Ancyrochitina, butbecause the appendices are incompletely preserved,

Ohio J. Sci. ORDOVICIAN-SILURIAN CHITINOZOANS 181

FIGURE 3-15. SEM micrographs of chitinozoans from the Belfast and the Preachersville.3-5 Ancyrochitina belfastensis n. sp. 3, oblique aboral view of OSU 38451 (holotype), sample H, 250X;4, detail of same specimen. Note the appearance of the appendix base 625 X; 5, lateral view of OSU 38452,sample H, 290X. 6-7. Ancyrochitina cf. A. primitiva Eisenack 1964. 6, lateral view of OSU 38453,sample H, 200X; 7, lateral view of OSU 38454, sample I, 245 X. 8-9- Ancyrochitina merga Jenkins 1970.8, lateral view of OSU 38455, sample A, 275 X. Note appearance of appendix; 9, lateral view of OSU38456, sample A, 215X. 10, Ancyrochitina sp., lateral view of OSU 38457, sample C, 300X. Noteappearance of appendix. 11-12, Conochitina cf. C. iklaensis Nestor 1980. 11, lateral view of OSU 38458,sample C, 135 X; 12, lateral view of OSU 38459, sample B, 130X. 13, Conochitina sp., lateral view of OSU38460, sample C, 145 X. 14-15, Cyathochitina campanulaeformis (Eisenack 1931). 14, lateral view of OSU38461, sample B, 205 X. Note longitudinal thickenings at flexure. 15, oblique aboral view of OSU 38462,sample D, 200 X.

182 Y. GRAHN AND S. M. BERGSTROM Vol. 85

specific determination is difficult. However, in sizeand overall morphology it shows similarity to speci-mens of Ancyrochitina described from the upper Ash-gillian and lower Llandoverian of Sweden (Grahn1978, 1982), the Llandoverian Medina Group, NewYork (Miller and Eames 1982), and the LlandoverianBecscie Formation, Anticosti Island (Achab 1981).Conochitina cf. C. iklaensis Nestor 1980 (fig. 11-12)

This form, which was found only in the Belfast,has a smooth subcylindrical vesicle with a broadlyrounded basal edge and a flat to concave base. Wecompare our specimens with Nestor's species becausethe basal scar described by Nestor has not beenobserved in the Belfast specimens. The size andlength: width ratio are, however, the same as in theEstonian species. In Estonia this species occurs in theRaikkilla Stage (C. cyphus toM. convolutus zones) andsimilar specimens have been described from the GunRiver Formation of Anticosti Island (Achab 1981).Specimens of C. iklaensis exhibit overall similarity tothose of the C. proboscifera group but differ in nothaving a protruding basal process and a concavebase. Also, the latter occur in younger strata thanthe former species.

Conochitina sp. (fig. 13)A Conochitina species similar to those noted by

Achab (1981, pi. 3: 1) as characteristic of the GunRiver Formation on Anticosti Island occurs in themiddle portion of the Belfast at the Ohio BrushCreek section. Compared to C. cf. C. iklaensis thisform has a broader basal part and the flanks taperinto a narrower aperture.Cyathochitina campanulaeformis (Eisenack 1931)

(fig. 14-15)This species, which is represented in both the

Belfast and in the overlying part of the Brassfield atthe Ohio Brush Creek locality, has the typical bell-shaped vesicle and longitudinal thickenings at theflexure. Similar specimens are common in Cara-docian through Wenlockian strata, the stratigraphi-cally youngest known ones being probably thosefrom the uppermost Wenlockian of Scania, Sweden(Grahn, unpubl. data).

LITERATURE CITEDAchab, A. 1977a Les chitinozoaires de la zone a

Dicellograptus complanatus de la Formation deVaureal, Ordovicien superieur, He d'Anticosti,Quebec. Can. J. Earth Sciences 14: 413-425.

1977b Les chitinozoaires de la zone aClimacograptus prominens elongatus de la Formationde Vaureal (Ordovicien superieur), He d'Anticosti,Quebec. Can. J. Earth Sciences 14: 2193-2212.

1981 Biostratigraphie par les chit-inozoaires del 1'Ordovicien Superieur-SilurienInferieur de l'lle d'Anticosti. Resultatspreliminaires. In: P. J. Lesperance (ed.), Subcom-mission on Silurian Stratigraphy, Ordovician-Silurian Boundary Working Group. FieldMeeting, Anticosti-Gaspe, Quebec 1981. Vol. 2:Stratigraphy and Paleontology, p. 143-157.

Bergstrbm, S. M., R. D. Evans, K. A. Knabe, andM.A. Miller 1981 Middle and Upper Or-dovician chitinozoan and graptolite bio-stratigraphy in the Cincinnati Region (Ohio,Kentucky, Indiana). Geol. Soc. America Ab-stracts with Programs 13: 408.

Berry, W. B. N. and A.J. Boucot 1970 Cor-relation of the North American Silurian rocks.Geol. Soc. America Spec. Paper 102: 1-289.

Brenchley, P.J. and G. Newall 1984 Late Or-dovician environmental changes and their effectson faunas. In: D. L. Bruton (ed.), Aspects of theOrdovician System. Palaeontol. Contr. Univ.Oslo No. 295. p. 65-79.

Chaiffetz, M. S. 1972 Functional interpretationof the sacs of Ancyrochitina fragilis Eisenack, andthe paleobiology of the ancyrochitinids. Jour. Pa-leontology 46: 499-502.

Cooper, B.J. 1975 Multielement conodontsfrom the Brassfield Limestone (Silurian) of south-ern Ohio. Jour. Paleontology 49: 984-1008.

Cramer F. H. and M. C. R. Diez de Cramer 1972North American Silurian palynofacies and theirspatial arrangement: Acritarchs. Palaeonto-graphicaAbt. B138: 107-180.

Eisenack, A. 1959 Neotypen baltischer Silur-Chitinozoen und neue Arten. Neues JahrbuchGeol. Palaeontol. Abh. 108: 1-20.

1964 Mikrofossilien aus dem Silur Got-lands. Chitinozoen. Neues Jahrbuch Geol.Palaeontol. Abh. 120: 308-342.

1968 tiber Chitinozoen des baltischenGebietes. Palaeontographica Abt. A131:137-198.

1970 Mikrofossilien aus dem Silur Est-lands and der Insel Osel. Geol. Fb'ren. StockholmFb'handl. 92: 302-322.

1977 Mikrofossilien in organischer Sub-stanz aus dem Middle Nodular Beds (Wenlock)von Dudley, England. Neues Jahrbuch Geol.Pala'ontol. Mh. Jahrg. 1977: 25-35.

Foerste, A. F. 1896 An account of the middleSilurian rocks of Ohio and Indiana. CincinnatiSoc. Natur. Hist. J. 18: 161-197.

Gordon, L. A. and F. R. Ettensohn 1984Stratigraphy, depositional environments and re-gional dolomitization of the Brassfield Formation(Llandoverian) in east-central Kentucky. South-eastern Geology 25: 101-115.

Grahn, Y. 1978 Chitinozoan stratigraphy andpaleoecology at the Ordovician-Silurian boundaryin Skane, southernmost Sweden. Sver. Geol. Un-ders. Ser. C744: 1-16.

— 1980 Early Ordovician Chitinozoa fromOland. Sver. Geol. Unders. Ser. C775: 1-41.

1981 Ordovician Chitinozoa from theStora Asbotorp boring in Vastergotland, south-central Sweden. Sver. Geol. Unders. Ser. C787:1-40.

1982 Caradocian and Ashgillian Chit-inozoa from the subsurface of Gotland. Sver.Geol. Unders. Ser. C788: 1-66.

OhioJ. Sci. ORDOVICIAN-SILURIAN CHITINOZOANS 183

and S. M. Bergstrom 1984 Lower Mid-dle Ordovician Chitinozoa from the SouthernAppalachians, United States. Rev. Paleobot.,Palynology 43: 89-122.

Gray, J. and A.J. Boucot 1972 Palynologicalevidence bearing on the Ordovician-Silurian para-conformity in Ohio. Geol. Soc. America Bull. 83:1299-1314.

Jenkins, W. A. M. 1970 Chitinozoa from theOrdovician Sylvan Shale of the Arbuckle Moun-tains, Oklahoma, Palaeontology 13: 261-288.

Knabe, K. A. 1980 Kirkfieldian (Middle Or-dovician) through Edenian (Upper Ordovician)chitinozoans from the Cincinnati Region of Ken-tucky. Unpubl. M.S. thesis, The Ohio StateUniv., Columbus. 153 p.

Kohut, J. J. and W. C. Sweet 1968 The Ameri-can Upper Ordovician Standard. X. UpperMaysville and Richmond conodonts from the Cin-cinnati region of Ohio, Kentucky, and Indiana.Jour. Paleontol. 42: 1456-1477.

Laufeld, S. 1967 Caradocian Chitinozoa fromDalarna, Sweden. Geol. Foren. Stockholm Fb'r-handl. 89: 275-349.

1971 Chitinozoa and correlation of theMolodova and Restevo Beds of Podolia, USSR.Mem. Bur. Geol. Min. 73: 291-300.

1974 Silurian Chitinozoa from Got-

Eesti NSV Teaduste Akadeemia, Keemia Geo-loogia 25: 319-323.

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