Ordovician chitinozoa from Tallinn, northern Estonia

Review of Palaeobotany and Palynology, 43 (1984): 5--31

5

Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

ORDOVICIAN CHITINOZOA FROM TALLINN, NORTHERN ESTONIA

YNGVE GRAHN'

Geological Survey of Sweden, Box 6 70, S- 751 28 Uppsala (Sweden) (Received July 4, 1984)

ABSTRACT Grahn, Y., 1984. Ordovician Chitinozoa from Tallinn, northern Estonia. Rev. Palaeobot. Palynol., 43: 5--31. The chitinozoans from three sections comprising Tremadocian to middle Caradocian strata in Tallinn, northern Estonia, have been investigated. Twenty-eight species of the genera Conochitina, Cyathochitina, Desrnochitina, Eisenackitina, Halochitina, Lagenochitina, Rhabdochitina, and Tanuchitina are described.

Conochitina crinita, C. cucumis, Cyathochitina? clepsydra, Desrnochitina papilla, and Tanuchitina tallinnensis are described as new species. The Chitinozoa are compared with those outside northern Estonia and with the type specimens. The chitinozoan palaeoecology is briefly discussed. INTRODUCTION

Estonia is situated east of the Baltic Sea (Fig.l) and is classical in chitinozoan research since the pioneer works by Eisenack. In northern Estonia the Ordovician has a thickness of about 180 m and the beds strike approximately E--W and dip in general ca. 0.25 ° towards the south. Most published information about Ordovician chitinozoans in the Baltic area originate from erratics of uncertain age and provenance, and very little from continuously sampled sections. Eisenack (1937, 1955, 1958, 1959, 1962a) was the first to describe Ordovician Chitinozoa with known provenance from Estonia. Through a series of papers by Estonian geologists, e.g. M~innil et al. (1968) and M~/nnil (1971, 1972a, 1976), Estonia became a comparatively well-investigated area in chitinozoan research. Special studies were made by Bachmann (1967} on chitinozoans from the kuckersite beds (Kukmse Stage), and Nblvak described chitinozoans at the Kukrusean/Idaverean boundary (1972) and in Ashgillian strata in Estonia (1980). M~innil (1972b), however, was the first to compare Ordovician Chitinozoa (e.g. Caradocian) from continuously sampled sections in east Baltoscandia (Estonia, Latvia) with west Baltoscandia (Sweden). A similar study was made by Grahn (1982a, pp.51--54) for Caradocian and 'Present address: Department of Geology and Mineralogy, The Ohio State University, Columbus, OH 43210 (U.S.A.). 0034-6667/84/$03.00

© 1 9 8 4 Elsevier S c i e n c e Publishers B.V.

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Ashgillian strata. These two studies showed that it is possible to correlate post-Llandeilian beds in the Baltoscandian region with chitinozoans. Eisenack (1972, 1976) and Wrona (1980} used Ordovician Chitinozoa from Estonia for morphological studies. Summaries of the Ordovician biostratigraphy were made by Eisenack (1962b, 1968) and R55musoks (1970}. Ordovician Chitinozoa from adjacent areas have been mentioned or described from southwestern Finland (Tynni, 1975}, Latvia (PSlma et al., 1977), Lithuania (Dicevitchius, 1970a, b, 1971) and European Russia (Umnova, 1969, 1973, 1976). The purpose of this study is to determine if a correlation based on chitinozoans is possible in pre-Caradocian beds between east and west Baltoscandia. During a visit in Estonia in 1981 three sections in Tallinn (Fig.l) were sampled continuously, viz. a section in the Suhkrum~igi quarry, a road-cut east of the old quarry at Lasnam~igi and a temporary exposure on the northern slope of Sbjam~igi (Figs.3--5). The sampled sequence comprises

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Pakerortian (Tremadocian) to lower Jbhvian (middle Caradocian) strata, except for upper Uhakuan and most of Kukrusean beds (Fig.2). With the exception of conodonts (Viira, 1966, 1970) in the Suhkrum~gi section, nothing is published about the micropaleontology in these three sections. During most of Ordovician time northern Estonia was situated in a shallow epicontinental sea, probably in a temperate climatic zone (Jaanusson, 1973). SAMPLES AND LOCALITIES In all, 76 samples from the three localities have been examined. Each of these samples was crushed to centimetre-sized pieces, then 50 g of the crushed sample as a standard were dissolved in hydrochloric, hydrofluoric and nitric acid. The residues were sifted (mesh distance 36 pm) after each acid treatment (Grahn, 1980, p.7). The organic residue was stored in water in shallow plastic beakers until being picked for SEM studies. The localities studied are described in stratigraphic order, and their positions are given in Fig.1.

Suhkrumiigi The lithology of the Suhkrum/igi quarry has been discussed by Orviku (1940, 1960), Viira et al. {1970)and Kaljo and Kivim/igi {1976). The sampled section (Fig.3) is situated at the southern entrance of the now abandoned quarry (locality 21 g of Orviku, 1940). The beds comprise a sequence from Pakerort (Tremadocian) to upper Lasnam~igi {upper Llanvirnian). Except for conodonts (Viira, 1966, 1970) and Tremadocian graptolites (Kaljo and Kivim/igi, 1976) nothing has been published previously on the fossils in the section. The stratigraphy used in this paper is based on Viira {1966, 1970), Viira et al. (1970), Kaljo and Kivim/igi (1976), LSfgren (1978, p.37) and R. M/innil (pers. commun., 1981).

Lasnam~igi The sampled section (Fig.4) is situated in a road-cut a b o u t 700 m east of the t y p e locality for the Lasnam~igi Stage (locality 21 c of Orviku, 1940), which is in the east part of an old quarry. The beds in the road-c~t comprise a sequence from upper Lasnam~igi (upper Llanvirnian) to middle Uhaku (middle Llandeflian). It should be added that the Uhakuan part is rich in discontinuity surfaces. M~innfl (1976) has described the graptolites in a section close to the one described in this paper. The Lasnam~igian/Uhakuan boundary has been drawn at the level of the first appearance of Gymnograptus linnarssoni in northern Estonia (M~innfl, 1976, and pers. commun., 1981), which is about 1.5 m below the boundary as defined by Orviku (1940) in Tallinn.

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SSjam~gi The sampled section (Fig.5) is from a temporary exposure on the northern slope of SSjam~igi, the highest point in Tallinn (55 m above sea level). The beds include uppermost Kukruse (lower Caradocian) to lower JShvi (middle

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t2 Caradocian). A distinct discontinuity surface which can be traced from northern Estonia (cf. Nblvak, 1972) to Sweden (Grahn, 1982a, p.18) marks the Kukrusean/Idaverean boundary. The thickness of the Idavere rocks decreases from south to north, and only the upper part is present in Tallinn (Jaanusson, 1945). The Idaverean/JShvian boundary is drawn at the level of the first appearance of Arnplexograptus cf. fallax in northern Estonia (M~/nnil, 1976, and pers. commun., 1981). This level coincides approximately with the level of the second bentonite above the Kukrusean/Idaverean boundary in southern Estonia (R. M~nnil, pers. commun., 1981), which probably is equivalent to the first bentonite above the boundary at SSjam~igi. CHITINOZOANS The dimensions given in the descriptions are in micrometers with an accuracy of + 2 ~m. The micrographs were taken on a Cambridge Mark II Stereoscan Electron Microscope (SEM) at 30 kV. Most of the investigated chitinozoans were preserved in full relief. All specimens illustrated are kept in the type collections of the Institute of Geology, Tallinn, Estonia.

Conochitina capitata Eisenack 1962 (Plate I, C--E) This Ordovician species has a stratigraphic range from the Lasnam~igi to Vormsi (lower Ashgillian) Stages. It has not been reported outside Estonia and Sweden. Those described from Serra de Buqaco, Portugal (Henry et al., 1974) are not conspecific. The specimens in this study are similar to those from the type stratum of Jbhvian age in the type locality at Aluvere (Allafer), northern Estonia.

Conochitina clavaherculi Eisenack 1959 (Plate I, F--G) C. clavaherculi is known from Baltoscandia and the U.S.A. (own observations). In Estonia it is reported from the Aseri to Uhaku Stages, whereas in Sweden it is known only from the K~lla Limestone of earliest Ubakuan age. The American specimens occur in the Lenoir Limestone of Alabama and Tennessee, and have about the same stratigraphical range as in Estonia. The specimens from the type locality at K~illa on Oland, Sweden, do not differ from those in Estonia and U.S.A. Conochitina conulus Eisenack 1955 (Plate I, H--I} The first appearance of this species is in the Didymograptus "bifidus" Zone. Outside Baltoscandia C. conulus has been reported from Normandy, France (Rauscher and Doubinger, 1967). In Estonia the species disappear in lower JShvi, and in Sweden somewhat later in the Nabala Stage (Grahn, 1982a). Eisenack (1955} described the holotype from a Baltic erratic boulder

13 with a lithology similar to the "Baukalkstein" in Tallinn. This limestone is of Lasnam~igian age, and C. conulus specimens of this age in Tallinn are also similar (cf. Plate I, H) to those illustrated by Eisenack (1955, plate 1: 1--3).

Conochitina crinita n. sp. (Plate I, A, B) Etymology: Latin, crinitus (= hairy), referring to the characteristic arrangement of the ornamentation. Holotype: Ch 807. Type stratum: Ubari Limestone, Aluoja Substage, Kunda Stage. Type locality: Suhkrum~igi section, Tallinn, northern Estonia. Description: Conochitina species with a conical body and a cylindrical neck that may widen at the aperture. The base is flat to convex and the basal edge rounded. The vesicle is covered by long simple spines. Dimensions: Total length 146--240, max. width 59--74, width of aperture 34--53, max. height of ornamentation 16. Remarks: Conochitina crinita differs from C. wesenbergensis in having considerably longer spines. It is easily distinguished from C. (Belonechitina) robardeti in that the flanks are straighter. Occurrence: North Estonia: Kunda, Lasnam~igi and Uhaku Stages. Conochitina cucumis n. sp. (Plate I, J--L) Etymology: Latin, cucumis (= cucumber), referring to the overall shape of the chitinozoan vesicle. Holotype: Ch 816. Type stratum: Lahepera Limestone, Langevoja Substage, Volkhov Stage. Type locality: S u h k r u m ~ i section, Tallinn, northern Estonia. Description: Conochitina species with a subcylindrical vesicle that tapers slightly towards a straight aperture. In general the rounded base has a small basal process. The vesicle wall is perfectly smooth. Dimensions: Total length 220--467, max. width 61--122, width of aperture 39--73. Remarks: Conochitina cucumis differs from C. minnesotensis in its much smaller size. Occurrence: North Estonia: Volkhov Stage. Conochitina elegans Eisenack 1931 (Plate I, M--N) C. elegans first appears in the Uhaku Stage in Estonia, and disappears in the Pirgu Stage (Ashgillian). It is also known from Gotland, Sweden (Grahn, 1982a), Welsh Borderland (Jenkins, 1967) and Sardinia, Italy (Laufeld, 1973). Eisenack (1931)described the holotype from a Baltic erratic boulder of lightgrey, fine-grained and limy sandstone with Cyathochitina campanulaeformis, Desmochitina nodosa and Spinachitina cervicornis. In addition to C. elegans this chitinozoan assemblage restricts the type stratum to somewhere in the

14 PLATE I

A,B. C--E.

F~G. H,I.

Conochitina crinita n. sp. Suhkrum~igi, Aluoja Substage, Kunda Stage. A. Holotype Ch 807. Lateral view, SEM x 180. B. Ch 808. Lateral view, SEM x 210. Conochitina capitata Eisenack 1962. C, D. SSjam~igi, Idavere Stage. E. Lasnam~igi, Lasnam~/gi Stage. C. Ch 809. Lateral view, SEM x 150. D. Ch 810. Aboral part in lateral view, SEM x 250. E. Ch 811. Lateral view, SEM x 80. Conochitina clavaherculi Eisenack 1959. Lasnam~igi, Uhaku Stage. F. Ch 812. Lateral view, SEM × 75. G. Ch 813. Lateral view, SEM x 95. Conochitina conulus Eisenack 1955. H. Lasnam~igi, Lasnam~igi Stage. Ch 814. Lateral view, SEM x 345. I. Lasnam~igi, Uhaku Stage. Ch 815. Lateral view, SEM x 300.

15

Gdisgfird Siltstone of Oanduan age. A neotype was described by Eisenack (1959) from a Baltic erratic boulder of unknown age. Conochitina micracantha Eisenack 1931 (Plate I, O, P) C. micracantha is a long-ranging species known from the Volkhov to Pirgu (Ashgillian) Stages in Baltoscandia. It has also been reported from Brittany, France (Paris, 1981}, Serra de Bugaco, Portugal (Paris, 1979), Alabama and Tennessee, U.S.A. (own observations), Oklahoma, U.S.A. (Jenkins, 1969), and Podolia, U.S.S.R. (Laufeld, 1971). The holotype is described from a Baltic erratic boulder of light-yellow limestone. C. micracantha dominates the chitinozoan fauna, b u t A canthochitina barbara and Rhabdochitina magna also occur. The chitinozoan fauna indicates that the type stratum is within the zone of Pleurograptus linearis. The Estonian specimens have their vesicle wall covered by simple spines in contrast to the Swedish specimens, where the degree of ornamentation varies stratigraphically (Grahn, 1980). Conochitina minnesotensis (Stauffer 1933) (Plate I, Q)

This species first appears in the Volkhov Stage and disappears in the Porkuni Stage (upper Ashgillian). C. minnesotensis is a widespread species and has also been reported from Sweden (Grahn, 1982a), Minnesota, U.S.A. (Stauffer, 1933), Alabama and Tennessee, U.S.A. (own observations), Oklahoma, U.S.A. (Jenkins, 1969), and Westphalia, F.R.G. (Eisenack, 1939). The holotype is from the lower Caradocian Decorah Formation at Ford Bridge, Minneapolis, Minnesota. The specimen illustrated by Stauffer (1933) seems to fall within the range of variation of the Baltoscandian specimens.

J--L.

Conochitina cucumis n. sp. Suhkrumiigi, Langevoja Substage, Volkhov Stage. J--K. Holotype Ch 816. J. Lateral view, SEM × 150. K. Aboral part in lateral view, SEM × 555. L. Ch 817. Lateral view, SEM × 150. M~N. Conochitina elegans Eisenack 1931. Lasnamiigi, Uhaku Stage. M. Ch 818. Lateral view, SEM × 100. N. Ch 819. Lateral view, SEM x 115. O,P. Conochitina micracantha Eisenack 1931. O. Lasnarn~gi, Uhaku Stage. Ch 820. Lateral view, SEM × 180. P. Lasnamiigi, Lasnam~igi Stage. Ch 821. Lateral view, SEM x 145. Q. Conochitina minnesotensis (Stauffer 1933). Lasnam~igi, Uhaku Stage. Ch 822. Lateral view, SEM x 50. R. Conoehitina cf. pellifera Eisenack. Lasnam~/gi, Lasnamiigi Stage. Ch. 823. Lateral view, SEM × 200. S,T. Conochitina primitiva Eisenack 1939. S. Suhkrum~igi, Aluoja Substage, Kunda Stage. Ch 824. Lateral view, SEM x 295. T. Suhkrumiigi, V~i~ina Limestone, Volkhov Stage. Ch 825. Lateral view, SEM × 170. U. Conochitina wesenbergensis Eisenack 1959. Suhkrum~igi, Viimsi Substage, Aseri Stage. Ch 826. Lateral view, SEM × 260.

Jr)

Conochitina cf. pellifera Eisenack 1959 (Plate [, R) This species is not reported outside Baltoscandia. C. pellifera is known from the Aseri to Idavere Stages. Specimens from the type locality at K~illa, (~land, Sweden are provided with long spines. In the material studied here most specimens have lost their ornamentation and many are distorted.

Conochitina primitiva Eisenack 1939 (Plate I, S, T) In the Baltoscandian area C. primitiva first appears in the Volkhov Stage and disappears in the Jbhvi Stage. It is also known from the Russian Platform (Umnova, 1969), Normandy and Calvados, France (Rauscher and Doubinger, 1967; Rauscher, 1970), Brittany, France (Paris, 1981), Serra de Buqaco, Portugal (Henry et al., 1974), and Westphalia, F.R.G. (Eisenack, 1939). The holotype was described from a Baltic erratic boulder of unknown age (Eisenack, 1934, p.62). In 1962 Eisenack introduced a neotype from the Aluojan (upper Kunda Stage) Limestone in Tallinn. In this study C. primitiva includes specimens from the neotype locality (cf. Plate I, S).

Conochitina wesenbergensis Eisenack 1959 (Plate I, U; II, A) The Estonian populations are similar to those in Sweden. The species is known from the uppermost Kunda to the Pirgu (Ashgillian) Stages. It is also known from Oklahoma, U.S.A. (Jenkins, 1969), Alabama and Tennessee, U.S.A. (own observations), and Podolia, U.S.S.R. (Laufeld, 1971). The holotype is described from the Rakvere Stage at Munalaskme (Munnalas), northern Estonia. The specimens from the type locality are similar with those from equivalent strata in Sweden (Grahn, 1982a).

Cyathochitina calix (Eisenack 1931) (Plate II, B--D) The first known appearance of C. calix in Baltoscandia is in the Volkhov Stage. The last specimens are reported from the Rakvere Stage. The species is also known from the Welsh Borderland (Jenkins, 1967), Brittany, France (Paris, 1981), Alabama and Tennessee, U.S.A. (own observations), and Westphalia, F.R.G. (Eisenack, 1939). Eisenack (1931) described the hototype from a light-grey limestone of u n k n o w n age. Associated chitinozoan species were Desmochitina cf. amphorea, Desmochitina cocca and Rhabdochitina magna. The type stratum might be a middle Ordovician limestone. A neotype was described by Eisenack (1962a) from the Volkhov Stage at J~igala (Jagowal), northern Estonia, and the figured specimens are similar to those from the Volkhov Stage at Tallinn (cf. Plate II, B).

Cyathochitina campanulaeformis (Eisenack 1931) (Plate II, E, F) In Baltoscandia C. campanulaeformis is a long-ranging species reported from the Volkhov Stage into the Silurian (zone of Monograptus triangulatus).

17 It is also known from the Welsh Borderland (Jenkins, 1967), Brittany, France (Paris, 1981), Westphalia, F.R.G. (Eisenack, 1939), Bohemia (Eisenack, 1948), Alabama and Tennessee, U.S.A. (own observations), and Podolia, U.S.S.R. (Laufeld, 1971). The Estonian specimens differ from those in Sweden in having smooth vesicles irrespective of geological age (Grahn, 1981a). The holotype was described from a Baltic erratic boulder of Oanduan (upper Caradocian) age. A neotype locality at Harku near Tallinn was introduced by Eisenack (1962a). The type stratum for the neotype is the Lasnam~igi Limestone.

Cyathochitina ? clepsydra n. sp. (Plate II, G, H) Etymology: Latin, clepsydra (= sandglass), referring to the overall shape of the chitinozoan vesicle. Holotype: Ch 833. Type stratum: Iru Limestone, Hunneberg Stage. Type locality: Suhkrumiigi section, Tallinn, northern Estonia. Description: Cyathochitina? species with a subconical vesicle. The base is flat. Orally of the basal edge the body is concave, then after 1/2--2/3 of the total length strongly widened toward the straight aperture. A characteristic lip is flaring sharply below the aperture. The carina is very short and often insignificant. The vesicle wall is perfectly smooth. Dimensions: Total length 120--196, max. width 110--196, width of aperture 85--135. Remarks: Cyathochitina? clepsydra differs from C. regnelli in having a much wider aperture with lip, and in having a smooth vesicle. Furthermore, C. ? clepsydra has a much smaller carina. Jenkinochitina vulgaris shows a striking similarity to C. ? clepsydra. Paris (1981) did not report any canna in J. vulgaris, although it can not be excluded that it has an insignificant carina (see Paris, 1981, plate 5: 1, 2, 3, 6, and 7). However, the attachment of the carina in Cyathochitina? clepsydra is not typical for Cyathochitina species, and it is therefore questionably referred to the genus. Occurrence: North Estonia: Hunneberg and Volkhov Stages. Upper Tremadocian, Siberian Platform (Obut, pers. commun., 1981). Lower Arenigian, Hongshiya Formation, Yunnan Province, China (own observations). Cyathochitina kuckersiana (Eisenack 1934) (Plate II, I, J) Its first appearance is in the Lasnamggi Stage, and it disappears in the Pirgu Stage (Ashgillian). It is also reported from Sweden (Grahn, 1982a), Normandy, France (Rauscher and Doubinger, 1967), Alabama and Tennessee, U.S.A. (own observations), and Podolia, U.S.S.R. (Laufeld, 1971). Eisenack (1934) described the holotype from the Kukruse Stage in Estonia. The type locality is unknown. In 1962 Eisenack chose a neotype locality at Halde, Metzingen, Wiirttemberg, F.R.G. The German specimens are similar to the Baltoscandian ones. According to Miinnil (1972a) C. kuckersiana has a

18 P L A T E II

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Conochitina wesenbergensis Eisenack 1959. Suhkrum~igi, Lasnam~igi Stage. Ch 827. Lateral view, SEM x 250. Cyathochitina calix (Eisenack 1931). B--C. Suhkrum~igi, V~i~ina Limestone, Volkhov Stage. D. Lasnam~igi, Lasnam~igi Stage. B--C. Ch. 828. B. Lateral view, SEM x 100. C. Aboral part in lateral view, SEM x 375. D. Ch 829. Lateral view, SEM X 150. Cyathochitina campanulaeformis (Eisenaek 1931 ). E. Lasnam~igi, Lasnam~gi Stage. Ch 830. Lateral view, SEM x 200. F. Suhkrumllgi, Lasnam~gi Stage. Ch 831. Lateral view, SEM x 225.

19

tendency to be exclusive with C. campanulaeformis in Estonia. This has not been confirmed by this study.

Cyathochitina regnelli Eisenack 1955 (Plate II, K, L) C. regneUi is restricted to the Baltoscandian area, where it is known from the Volkhov to Aseri Stages. The Estonian specimens are similar to those from the type stratum (Hunderum Limestone) in the type locality at Fj~icka, Dalarna, Sweden. Cyathochitina striata (Eisenack 1937) (Plate II, M, O) This species occurs in the Aseri to lowermost Kukruse Stages. The "type stratum" is a grey limestone of unknown age and provenance. The ornamentation of the holotype illustrated by Eisenack (1937) is unusual for C. striata, but a similar specimen was found in the Aseri Stage in the Suhkrum~igi section (Plate II, M).

Desmochitina amphorea Eisenack 1931 (Plate III, A, B) D. amphorea is known from the Lasnam~igi to Rakvere Stages. It is also reported from the Welsh Borderland (Jenkins, 1967). The holotype as defined by Eisenack (1931, p.93) consists of a chain of vesicles and probably is a specimen of Desmochitina nodosa according to the definition of this species by Eisenack (1931, p.92). As discussed by Grahn (1981b), typical specimens of Desmochitina arnphorea do not occur in chains. Obviously, a revision of this species will be necessary. Desmochitina complanata Eisenack 1932 (Plate III, C, D) D. complanata first appears in the upper Kunda Stage and is not known from strata younger than the Vormsi Stage (lower Ashgill). It is also reported from the Welsh Borderland (Jenkins, 1967). The type stratum consists of a whitish limestone with pyrite-concretions of unknown age. The lithology indicates, however, a late Caradocian age. Eisenack (1959) described a neotype G, H.

Cyathochitina?clepsydra n. sp. Suhkrum~gi, Iru Limestone, Hunneberg Stage.

G. Ch 832. Oblique lateral view, SEM × 230. H. Holotype Ch 833. Lateral view, SEM × 200. I, Z. Cyathochitina kuckersiana (Eisenack 1934). S6jam~igi, JShvi Stage. I. Ch 834. Lateral view, SEM × 160. J. Ch 835. Lateral view, SEM × 170. K , L . Cyathochitina regnelli Eisenack 1955. Suhkrum~gi, Aluoja Substage, Kunda Stage. K. Ch 836. Lateral view, SEM × 265. L. Ch 837. Lateral view. Note the ornamentation on the surface, SEM × 275. M--O. Cyathochitina striata (Eisenack 1937). M. Suhkrun~igi, Viimsi Substage. Aseri Stage. Ch 838. Lateral view. Note the vesicle ornamentation, SEM x 50. N. Lasnam~gi, Uhaku Stage. Ch 839. Lateral view, SEM × 40. O. Subkrurn~igi, Lasnam~igi Stage. Cb 840. Lateral view, SEM × 100.

2O PLATE IlI

21 from a middle Ordovician limestone of unknown age and provenance. The specimens in this study have a smooth vesicle in contrast to some specimens from Sweden (Grahn, 1982a).

Desmochitina minor Eisenack 1931 (Plate III, E, F) This Ordovician species is the longest ranging in Baltoscandia. The first specimens appear in the Hunneberg Stage and the species disappears in the Porkuni Stage (upper Ashgill). It is also known from Serra de Buqaco, Portugal (Paris, 1979), Oklahoma, U.S.A. (Jenkins, 1969) and Podolia, U.S.S.R. (Laufeld, 1971). The neotype (Eisenack, 1962a) is not conspecific with the holotype described by Eisenack in 1931. The holotype is a Desmochitina nodosa specimen according to the definition of this species by Eisenack (1931, p.92). The neotype is from the Volkhov Stage at J~igala (Jagowal), northern Estonia. Similar specimens are found in the Volkhov Stage at Tallinn.

Desmochitina nodosa Eisenack 1931 (Plate III, G, H) D. nodosa is known from the Idavere to Rakvere Stages in Baltoscandia. Eisenack (1931) described the holotype from a Baltic erratic boulder of Oanduan age. Desmochitina papilla n. sp. (Plate III, I, J) Etymology: Latin, papilla (= nipple), referring to the shape of the basal process. Holotype: Ch 849. Type stratum: TelinSmme member, V~i~inaLimestone, Volkhov Stage. Type locality: S u h k r u m ~ i section, Tallinn, northern Estonia. Description: Desmochitina species with an ellipsoidal vesicle. The base is convex and provided with a basal process. The body is provided with a short PLATE III A~ S. Desmochitina amphorea Eisenack 1931. A. SSjamiigi, JShvi Stage. Ch. 841. Lateral view, SEM × 390. B. SSjamilgi, Idavere Stage. Ch 842. Lateral view, SEM × 455. C, D. Desmochitina complanata Eisenack 1932. C. Lasnam~igi, Lasnam~igi Stage. Ch 843. Oblique oral view, SEM × 480. D. Suhkrum~igi, Valaste Substage, Kunda Stage. Ch 844. Oblique oral view, SEM × 500. E~ F. Desmochitina minor Eisenack 1931. Lasnam~igi, Lasnam~igi Stage. E. Ch 845. Oblique]ateral view, SEM X 400. F. Ch 846. Lateral view, SEM X 405. G,H. Desmochitina nodosa Eisenack 1931. SSjam~igi, Idavere Stage. G. Ch 847. Lateral view, SEM × 510. H. Ch 848. Oblique oral view, SEM × 550. I, J. Desmochitina papilla n. sp. Suhkrum~igi, V~iiina Limestone, Volkhov Stage. I. Holotype Ch 849. Lateral view, SEM × 270. J. Ch 850. Lateral view, SEM × 325. K , L . Desmochitina rugosa Eisenack 1962. K. Lasnam~gi, Lasnamilgi Stage. Ch 851. Lateral view, SEM x 290. L. SSjam~igi, Kukruse Stage. Ch 852a-b. Two specimens in lateral view, SEM × 240.

22 cylindrical neck and the collar is conical to subcylindrical. The vesicle wall is smooth. Dimensions: Total length 122----159, max. width 61--84, width of aperture 36--59. Occurrence: North Estonia: Volkhov Stage. Desmochitina rugosa Eisenack 1962 (Plate III, K, L) D. rugosa has not been reported outside Baltoscandia, where it is known from the Volkhov to JShvi Stages. The type locality is situated at Kunda-Aru in northern Estonia and the type stratum is a middle Ordovician limestone of Aserian--Lasnam~igian age. Specimens from the same stratigraphic interval in Tallinn are similar. Eisenackitina cf. oelandica (Plate IV, A, B)

This species is known from upper Kukruse to Rakvere Stages in Baltoscandia. Specimens of E. oelandica from the type stratum (Kukruse Stage) at BSda Hamn, C)land, Sweden are smooth in contrast to E. cf. oelandica. Halochitina retracta (Eisenack 1955) (Plate IV, C, E} H. retracta is known from the Lasnam~igi to Kukruse Stages. It is not reported outside Estonia. The t y p e locality is situated at Harku near Tallinn. The type stratum is not exactly known. The specimens herein are similar to those from the type locality. Lagenochitina esthonica Eisenack 1955 (Plate IV, F, G)

In Baltoscandia L. esthonica is the oldest chitinozoan species reported so far, and it appears already in late Tremadocian beds from Sweden (Grahn, 1980). It is also known from beds of the same age in the Siberian Platform (Obut, pers. commun., 1981) and from the lower Arenigian Hunghuayuan Formation in the Hubei Province, China (own observations). In northern Estonia it first appears in the Hunneberg Stage. The species is also reported from the Welsh Borderland (Jenkins, 1967), Brittany, France (Paris, 1981), Spitsbergen (Bockelie, 1980), and Quebec, Canada (Achab, 1980). L. esthonica is not known from strata younger than the Kunda Stage. The holotype is from the Volkhov Stage at Paldiski (Baltischport), northern Estonia. Rhabdochitinagracilis Eisenack 1962 (Plate IV, H, I)

This Ordovician species is not known outside Baltoscandia, where it occurs from the Volkhov to Porkuni (upper Ashgillian) Stages. The holotype is described from the lower Kunda Stage at Fjgcka, Dalarna, Sweden. The Estonian specimens fall within the range of variation of those from the type locality.

23

PLATE IV

~i ¸ /~:~i

iil~i.~~

Eisenackitina cf. oelandica. Sbjam~igi, Kukruse Stage. A. Ch 853. Lateral view, SEM X 475. B. Ch 854. Lateral view, SEM x 515. C--E. Halochitina retracta (Eisenaek 1955). Lasnamiigi, Lasnam~igi Stage. C. Ch 855. Oblique oral view, SEM x 260. D. Ch 856. Oblique oral view, SEM × 340. E. Ch 857. Lateral view, SEM X 250. F~ G. Lagenochitina esthonica Eisenack 1955. Suhkrum~igi, V~ina Limestone, Volkhov Stage. F. Ch 858. Lateral view, SEM x 120. G. Ch 859. Oblique lateral view, SEM x 125. H , I . Rhabdochitina gracilis Eisenack 1962. Lasnam~igi, Uhaku Stage. H. Ch 860. Lateral view, SEM × 50. I. Ch 861. Lateral view, SEM × 55. J--M. Tanuchitina tallinnensis n. sp. Suhkrum~igi, V~/~na Limestone, Volkhov Stage. J, L. Ch 862. J. Lateral view, SEM × 75. L. Aboral view, SEM × 685. K, M. Holotype Ch 863. K. Lateral view, SEM × 75. M. Aboral view, SEM × 690. A,B.

24

Tanuchitina tallinnensis n. sp. {Plate IV, J--M) Etymology: Latin, tallinnensis ~= inhabitant of Tallinn), referring geographi cally to the Tallinn area. Holotype: Ch 863. Type stratum: Lahepera Limestone, Langevoja Substage, Volkhov Stage. Type locality: Suhkrum/igi section, Tallinn, northern Estonia. Description: Tanuchitina species with a slender, subcylindrical vesicle which tapers towards the straight aperture. The base is flat. The basal edge is provided with a short and massive earina. The vesicle wall is smooth. Dimensions: Total length 415--830, max. width 61--98, width of aperture 36--49, max. length of carina 7. Remarks: Tanuchitina tallinnensis differs from T. bergstroemi in not having a membranous carina. T. achabae has a less cylindrical vesicle and a larger and more membranous carina (Paris, 1981, plate 4: 13). Tanuchitina domfrontensis is smaller than T. tallinnensis, and it has a well-developed muero that resembles an inner membranous carina (Paris, 1981, plate 8: 10). Occurrence: North Estonia: Volkhov to Lasnam~igi Stages. CHITINOZOAN BIOSTRATIGRAPHY AND CORRELATION The stratigraphical ranges of the chitinozoan species are shown in Figs.3--5. Half of the 28 chitinozoan species discussed here have been reported outside Baltoscandia, but they are mostly long-ranging and without major stratigraphic significance. It is not possible to correlate the Kunda and Aseri Stages between northern Estonia and Sweden with chitinozoans. Most of the Kunda Stage is missing in northwestern Estonia (Fig.2), and in the Swedish mainland the Aseri Stage consists of red limestones indicating diagenetic environments with oxidizing conditions, which probably prevented preservation of the chitinozoans (Grahn, 1981b, pp.30--31).

Hunneberg and Billingen The oldest known chitinozoans from Estonia appear in the Hunneberg Stage (upper Paroistodus proteus Zone), but no chitinozoans have been reported from contemporaneous strata in Sweden. However, a divergent chitinozoan fauna is known from the Billingen Stage (Oepikodus evae Zone) in V/istergStland, south-central Sweden (Grahn, 1981b, p.25), but these chitinozoans are unfortunately poorly preserved and the determinations are uncertain. The only sample in this study which yielded chitinozoans from the Hunneberg Stage shows an abundance of 2.3 specimens per gram of rock.

25

Volkhov Conochitina cucumis and Desmochitina papilla are t w o good indicators for Volkhovian beds in northern Estonia since they both seem to be restricted to the Volkhov Stage. Ten chitinozoan species appear for the first time all over Baltoscandia in the Volkhov Stage, viz. Conochitina micracantha, C. minnesotensis, C. primitiva, Cyathochitina calix, C. campanulaeformis, C. regnelli, Desmochitina elongata (not seen in this study), D. rugosa, Rhabdochitina gracilis, and Tanuchitina tallinnensis. The abundance of chitinozoans in the Volkhov Stage is generally below 3 specimens per gram of rock, with a maximum of 5.8 specimens. Kunda The lowermost part of the Kunda Stage in northwestern Estonia (0.2 m in Tallinn) is equivalent to the upper Valaste Substage (upper Eoplacognathus ? variabilis Zone). At this level Conochitina conulus and Desrnochitina complanata appear for the first time in Baltoscandia. The Kunda Stage at Tallinn is mostly of Aluojan age (upper Didymograptus "bifidus" Zone). The first known appearance of Conochitina crinita and C. wesenbergensis is in the upper part of the "bifidus" Zone, and Lagenochitina esthonica disappears in these beds all over Baltoscandia. In general the abundance of chitinozoans is 1--4 specimens per gram of rock, with a maximum of 8.1 specimens.

Aseri The lower part of the Aseri Stage is absent in the Tallinn area. In the upper part Conochitina clavaherculi, C. pellifera and Cyathochitina striata make their d e b u t in Baltoscandia, and in the same beds is the last known occurrence of Cyathochitina regnelli. No chitinozoans from the Aseri Stage are known from Sweden. The abundance of chitinozoans is 1.6--5.7 specimens per gram of rock.

Lasnamtigi The Rebala Limestone constitutes the lower part of the Lasnamiigi Stage (lower Pygodus serra Zone --Eoplacognathus foliaceus Subzone) in northern Estonia. In this stratigraphical unit Cyathochitina kuckersiana and Halochitina retracta appear for the first time in Baltoscandia. In the lowermost part of the Rebala Limestone Tanuchitina tallinnensis disappears. Conochitina capitata and Desmochitina amphorea have their first known occurrence in the Pae Limestone of late Lasnam~igian age (middle Pygodus serra Zone-Eoplacognathus reclinatus Subzone). It is not possible to correlate the Lasnam~igian/Uhakuan boundary between northern Estonia and Sweden by means of chitinozoans.

26 In general the abundance of chitinozoans is less than 2 specimens per gram of rock in lower Lasnam~igi and 7--15 specimens in upper Lasnam/igi, with a maximum of 6.9 and 48.4 specimens, respectively.

Uhaku Uhakuan beds crop out in Tallinn, and the Toompea castle is built on a hill of Uhakuan limestone. The total thickness in the Tallinn area is estimated to be about 10 m (Miinnil, 1976, p.107). The sampled section in the road-cut at Lasnamiigi is 4.92 m thick, and ends in the lowermost part of the Pygodus anserinus Zone. In the Tallinn area a c o n o d o n t subzone with Eoplacognathus bergstroemi can be separated within the Pygodus serra Zone 1.5--2.2 m above the Lasnamiigian/Uhakuan boundary (R. M/innil, pers. commun., 1981). At the base of this subzone Conochitina elegans appears for the first time in Baltoscandia. In the Lasnam~igi section Conochitina crinita and C. clavaherculi disappear in the upper part of the road-cut. In Sweden Cyathochitina striata disappears at the Uhakuan/Kukrusean boundary and somewhat earlier in northern Estonia (M~innil, 1976, p.107). In general the abundance of chitinozoans is 5--10 specimens per gram of rock, with a m a x i m u m of 21.3 specimens.

Kukruse In a boring at Lehmja (Fig.l), about 6 km south of Sbjamggi, the thickness of the Kukruse Stage is 10.33 m (R. M/innil, pers. commun., 1981). R55musoks (1970, p.162) reported a thickness of 9.64 m in a boring at Mbigu (Fig.l), about 3 km southwest of SSjam/igi. However, in northern Estonia the uppermost part is missing (R. M/innil, pers. commun., 1981). In the temporary exposure at SSjamggi only 0.34 m was accessible. Cyathochitina stentor and Halochitina retracta disappear in the Kukruse Stage. According to M/innil (1972a) recurrent chitinozoan associations occur in this stage in northern Estonia. Eisenackitina oelandica and E. oelandica together with Cyathochitina calix alternate with barren intervals. M//nnil explained this distribution as caused by some rhythmic abiotic factor. It is uncertain whether Miinnil's Eisenackitina oelandica is conspecific with E. cf. oelandica in this study. Eisenackitina cf. oelandica appears for the first time in the Kukruse Stage. The chitinozoan abundance in the two samples investigated is 4 and 36.7 specimens per gram of rock, respectively.

Idavere In Baltoscandia three chitinozoan species, viz. Angochitina communis, Cyathochitina reticulifera and Eremochitina dalbyensis, are characteristic for the Idavere Stage. None of these species were f o u n d in the section at S S j a m ~ i , where the thickness of the Idavere Stage probably is 0.36 m. The first known occurrences of Desmochitina nodosa all over Baltoscandia is in these beds.

27 The chitinozoan abundance is in general below 3 specimens per gram of rock, with a maximum of 26.8 specimens.

J6hvi The total thickness of the JShvi Stage in the Tallinn area is > 6 . 2 m (R55musoks, 1970). No characteristic chitinozoan species have been found in the Jbhvi Stage during this study, b u t Conochitina primitiva and Desmochitina rugosa have their last known appearance in this stage. At present there is no unequivocal correlation between the JShvi Stage in northern Estonia and contemporaneous strata in Sweden (for discussion, see Jaanusson, 1976). T w o chitinozoan species might be of some importance. Spinachitina multiradiata appears for the first time in northern Estonia at the Idaverean/ Jbhvian boundary (R. M~nnil, pers. commun., 1981). In Sweden it is known from the uppermost part of the Dalby Limestone (Amorphognathus tvaerensis Zone -- Prioniodus alobatus Subzone). Another key species for the correlation is Spinachitina cervicornis. This species first appears in the uppermost JShvi Stage in Estonia (R. MRnnil, pers. commun., 1981) and in the Skagen Limestone (lower Amorphognathus superbus Zone) in Sweden. The abundance of chitinozoans is below 3 specimens per gram of rock. REMARKS

ONPALAEOECOLOGY

The closest land area during Ordovician time was situated somewhere in the north and probably embraced most of Finland (M/~nnil, 1966). Oolitic beds in the l o w e r - a n d middle Ordovician, and reef-like structures in the uppermost middle (Oandu Stage) and u p p e r m o s t (Porkuni Stage) Ordovician suggest shallow water during Ordovician time at least occasionally in northern Estonia (cf. M/innil, 1966; Jaanusson, 1973). The normal Ordovician carbonate sediment in Baltoscandia was a mixture of skeletal sand (detrite) and carbonate mud with some terrigenous m u d (Jaanusson, 1973, p . l l ) . It is difficult to reconstruct the bathymetrical conditions in the Baltoscandian Basin because the deposition t o o k place on an extremely flat sea floor in an extensive sea. Furthermore, the general depositional conditions have virtually no modern analogues (Jaanusson, 1982, p.5). In this study limestones with a high content of skeletal sand are considered as deposited in higher energy water than those with a lower content of skeletal sand grains. A high water energy probably reflects shallow water. Sandstones and a wellsorted calcareous s i l t s t o n e with calcareous algae (Cyclocrinus sp.) indicate very shallow water. Mud and graptolitic shale in itself only reflects low water energy, b u t the macrofossils can be of some help in determining the depth. Our knowledge a b o u t chitinozoan faunas in the graptolitic shales is deficient, b u t the chitinozoans seem to have a lower diversity in graptolitic facies than in shelly facies. When plotting the Ordovician chitinozoan species in Baltoscandia against the lithologies, it turns o u t that many of them have a distribution covering most of the lithologies, while others are more restricted.

25 Some of the chitinozoans reached specific types of rocks suggesting environments. In northern Estonia Conochitina show preference for limestones with

their m axi m um relative frequencies in a preference for certain depositional

clavaherculi and Rhabdochitina gracilis a low c o n t e n t of mud, and Conochitina capitata, C. minnesotensis, Cyathochitina kuckersiana, C. striata, Desmochitina nodosa, and D. papilla for limestones with a high c o n t e n t of mud. Laufeld (1974, p.121) f ound that the chitinozoan abundance increased wi'~h the amo u n t of terrigenous mud in the Silurian of Gotland, Sweden. His conclusion has n o t been confirmed by this study. Th e preference for certain lithologies can of course be a h y d r o d y n a m i c sorting effect, but the evidence discussed below favours an ecological explanation. Glauconitic limestones with a high c o n t e n t of skeletal sand show m a x i m u m frequencies for Cyathochitina regnelli in nort hern Estonia as well as in Sweden. A palaeoecological reconstruction of such an envi ronm ent in northwest (~land, southeast Sweden, indicated a depth of some tens of meters or less (Grahn, 1982b, p.12). Cyathochitina regnelli is a small species, but in this en v ir o n ment also Lagenochitina esthonica reached high frequencies, and this species is one of the largest chitinozoan species in Baltoscandia. The cooccurrence of these two species seems to exclude mechanical or a u t o c h t h o n o u s sorting as being responsible for the distribution of them. As a rule chitinozoans of different sizes occur in the same sample, and there is also an intraspecific size variation. This can only be explained by an ecological control. Because the chitinozoans are considered as eggs or egg capsules of marine metazoans (Grahn and Afzelius, 1980), it is convenient to use the term c h itin o zo o p h o r a ns (sensu Grahn, 1981b, p.30) for these supposed metazoans when discussing the ecology. Regarding the wide geographical distribution of m any Baltoscandian species and their independence of lithologies, a neritic pelagic way of life for m a n y chitinozoophorans seems probable, at least during spawning. However, m an y chitinozoans show preference for certain sediments, and this distribution can n o t be explained by a neritic pelagic life of the chitinozoophorans. The distribution of the c hi t i noz oophor ans was n o t necessarily depthdependent. Physical factors like t e m p e r a t u r e and salinity or the current conditions might be just as important. A restricted occurrence of chitinozoans may depend on c hi t i noz oophor ans that had a short duration of the egg and larval stages; some of t hem probably also attached their eggs or egg capsules to firm objects. A n e k t o b e n t h i c way o f life can n o t be excluded for these c hitinoz o oph orans. ACKNOWLEDGEMENTS Lemb it P~)lma (Tallinn) provided me with lithologs and helped me in the field together with Madis Rubel (Tallinn). Ralph M~innil (Tallinn) kindly discussed various stratigraphical problems and Ordovician Chitinozoa from

29 E s t o n i a w i t h m e . J a a k N S l v a k (Tallinn) was o f g r e a t help during m y visit in Tallinn, h e l p e d m e in the field and discussed O r d o v i c i a n C h i t i n o z o a f r o m n o r t h e r n E s t o n i a w i t h m e . T h a n k s also t o all colleagues, n o t m e n t i o n e d individually here, in T a l l i n n a n d T a r t u t h a t m a d e m y visit in E s t o n i a rewarding. T h e m a n u s c r i p t has b e e n i m p r o v e d b y c o m m e n t s f r o m V a l d a r J a a n u s s o n ( S t o c k h o l m ) , Sven L a u f e l d ( U p p s a l a ) a n d R o b e r t F. L u n d i n ( T e m p e , A R ) . A n n - C h r i s t i n e SjSberg ( U p p s a l a ) a n d I n g a P a l m a e r ( U p p s a l a ) finished m y line drawings. T h e R o y a l Swedish A c a d e m y o f Sciences ( S t o c k h o l m ) , R o y a l Swedish A c a d e m y o f E n g i n e e r i n g Sciences ( S t o c k h o l m ) a n d A c a d e m y o f Sciences o f t h e E s t o n i a n S.S.R. (Tallinn) t h r o u g h D i m i t r i Kaljo (Tallinn) s u p p o r t e d m y visit in E s t o n i a financially. My sincere t h a n k s t o all o f these friends and o r g a n i z a t i o n s . REFERENCES Achab, A., 1980. Chitinozoaires de l'Arenig inf6rieur de la Formation de L~vis (Qu6bec, Canada). Rev. Palaeobot. Palynol., 31: 219--239. Bachmann, A., 1967. Mikropal~iontologische Untersuchungen a m Kuckersit-Kalk. Mikro-

kosmos, 56: 371--375. Bockelie, T.G., 1980. Early Ordovician Chitinozoa from Spitsbergen. Palynology, 4: 1--14. Dicevitchius, E., 1970a. Fauna khitinozoa ordoviko-siluriiskikh otlozheniy Litvy i ee stratigraficheskoe znachenie. Dokl. Akad. Nauk S.S.S.R., 193: 884--887. Dicevitehius, E., 1970b. Some new species of Chitinozoa from Ordovician and Silurian deposits of the south Baltic and of northwestern Byelorussia. 1. Acanthochitina and some Conochitina. In: Paleontology and Stratigraphy of Pribaltic and Byelorussia. Nauka, Moscow, pp.5--18 (in Russian). Dicevitchius, E., 1971. Some new species of Chitinozoa from Ordovician and Silurian deposits of the south Baltic and northwestern Byelorussia. 2. Sphaerochitina. In: Paleontology and Stratigraphy of Pribaltic and Byelorussia. Nauka, Moscow, pp.77--95 (in Russian). Eisenack, A., 1931. Neue Mikrofossilien des baltischen Silurs.I.Paliiontol.Z., 13: 74--118. Eisenack, A., 1932. Neue Mikrofossilien des baltischen Silurs. II. Pal~ontol. Z., 14: 257--277. Eisenack, A., 1934. Neue Mikrofossilien des baltischen Silurs. III,und neue Mikrofossilien des bShmischen Silurs.I. Pal~iontol.Z., 16: 52--76. Eisenack, A., 1937. Neue Mikrofossilien des baltischen Silurs. IV. Pal~iontol. Z., 19: 218--243. Eisenack, A., 1939. Chitinozoen und Hystrichosphaeriden im Ordovizium des Rheinischen Schiefergebirges. Senckenbergiana, 21: 135--153. Eisenack, A., 1948. Mikrofossilien aus Kieselknollen des bShmischen Ordoviziums. Senckenbergiana, 28: 105--117. Eisenack, A., 1955. Neue Chitinozoen aus d e m Silur des Baltikums und d e m Devon der Eifel. Senckenbergiana Lethaea, 36: 311--319. Eisenack, A., 1958. Mikrofossilien aus d e m Ordovizium des Baltikums. 1. Markasitschicht, Dictyonema-Schiefer, Glaukonitsand, Glaukonitkalk. Senckenbergiana Lethaea, 39:

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