New biostratigraphically important chitinozoans from the kukruse regional stage, upper ordovician of baltoscandia/Uued biostratigraafiliselt olulised kitiinikud Baltikumi Kukruse lademest (Ulem-Ordoviitsium).
Chitinozoans are an important biostratigraphical tool for dating and correlating Ordovician sections. The data on the distribution of the new species described herein are based on more than 2000 samples, collected mainly from drill cores and processed for obtaining information on the biostratigraphy of chitinozoans. All the chitinozoan taxa encountered in the sections from this stratigraphical interval are not illustrated here (Fig. 1), but are available in papers listed below under 'Occurrences'. The described species are restricted to the Eisenackitina rhenana chitinozoan Subzone of the Laufeldochitina stentor Zone (Nolvak & Grahn 1993; Nolvak et al. 2006). Their short temporal ranges in the proximity of the Darriwilian/Sandbian global stages boundary point to the great biostratigraphical value for correlation purposes. Figure 1 shows temporal ranges of these species in the Kerguta (565) and Savala drill core sections in central and northeastern Estonia, respectively, as well as their relative relationships to each other. As all findings of Conochitina savalaensis are limited to the commercially mineable kukersite oil shale beds A-[F.sub.2] in the Estonia oil shale deposit, NE Estonia (see Bauert & Kattai 1997), this species can be used for tracing coeval beds across the Palaeobaltic basin. All described specimens are stored at the Institute of Geology at Tallinn University of Technology.
Incertae sedis group CHITINOZOA Eisenack, 1931 Order PROSOMATIFERA Eisenack, 1972 Family CONOCHITINIDAE Eisenack, 1931, emend. Paris, 1981
Subfamily CONOCHITININAE Paris, 1981 Genus Conochitina Eisenack 1931, emend. Paris et al. 1999
Conochitina savalaensis sp. nov. Figure 2
1981 Eisenackitina oelandica (Eisenack 1955); Grahn, fig. 15D.
2006 Conochitina sp. 1; Nolvak & Bauert, pl. I, fig. 1.
Derivation of name. The species name refers to the locality name Savala (a settlement in NE Estonia), which is the site of the Savala drill core.
Holotype. GIT 660-1666; Fig. 2A; Viljandi drill core, 373.8 m, Kukruse Regional Stage (RS).
Type locality and horizon. Viljandi drill core, 373.3-374.3 m, the Kivioli Member of the Viivikonna Formation, lower part of the Kukruse RS, lowermost Sandbian.
Dimensions (gm). Holotype: total length--L: 140; maximal chamber diameter--Dp: 67; diameter of neck (oral tube)--Dc: 40. The biometric data for 30 specimens from the Saare (K-20), Vihterpalu (1103), Virtsu (F-309), Kerguta (565) and Bliudziai (150) sections are: L: 92-202, mean 140; Dp: 54-82, mean 67; Dc: 32-48, mean: 39.
Diagnosis. A short Conochitina species with a clear flexure and shoulder, both the slightly claviform chamber as well as the neck are of nearly equal length; the convex base shows a mucron and a concentric ridge; the vesicle wall has a microgranulous surface and the aperture is straight.
Description. Rare specimens may have an inconspicuous flexure, however, both the chamber and the neck are more or less clearly differentiated, having the same length. The chamber walls are slightly convex, with the greatest width at about half the chamber length, the neck is cylindrical, with a straight aperture. The basal margin is broadly rounded. Some specimens have a rather flat base, without the concentric ridge developed, but then showing a central scar. At high magnifications the micro-granulous outer surface is revealed.
Discussion. This species has some similarities with Silurian Conochitina tuba Eisenack, especially in some details of the base (see Laufeld 1974, fig. 36). However, C. savalaensis is smaller and its chamber and neck are more clearly differentiated. Conochitina savalaensis is to some extent close to C. parva in the vesicle shape and dimensions. However, important diagnostic details of the base remain unknown, because Umnova (1981) described Conochitina parva with only silhouette photos. According to Umnova, C. parva has an extended temporal distribution through the whole Middle Ordovician to the Kukruse Stage (Talsi core, Latvia). Our abundant records of C. savalaensis from the East Baltic, however, exhibit a limited temporal range, being restricted to the lower part of the Eisenackitina rhenana Subzone within the Laufeldochitina stentor chitinozoan Zone (Nolvak & Grahn 1993; Nolvak et al. 2006).
Occurrence. The previously published records of C. savalaensis are:
Conochitina savalaensis nom. nud.; Mannil 1976, fig. 2; 1986, fig. 2.1.1; Modlinski et al. 2002a, fig. 4, 2002b, fig. 3.
Conochitina nov. sp. A; Bauert & Bauert 1998, app. 14.
Conochitina sp. 1; Nolvak 1999, app. 6, 2002, fig. 4, 2003, app. 23, 2005, app. 27, 2008, app. 6, sheet 3, 2010, app. 6; Saadre et al. 2004, fig. 7; Nolvak & Bauert 2006, pl. I, fig. 1, app. 9; Hints et al. 2014, fig. 2.
Altogether several hundred specimens have been found in strata of the lower Kukruse RS in Baltoscandia, including the following sections: in Estonia--Savala, from two intervals 20.4-21.4 m and 25.3-26.0 m; Kerguta (565), 161.1-161.6 m; Rapla, 166.5 m; Velise (F-97), 211.3-213.3 m; Ulemiste (2), intervals 17.1-17.7 and 20.1 m; Vihterpalu (375), 38.1 m; Ohesaare, 483-484.0 m; Mannamaa (F-367), 167.8-168.1 m; Viki, 342.7-344.8 m; Viru underground mine and Kohtla opencast sections (Hints et al. 2007); in Latvia--Aizpute-41, 1065.1 m; Baldone, 868.4-869.8 m; Baltinava, 706.5-709.4 m; in Lithuania--Bliudziai (150), 1379.0-1379.6 m; Ukmerge, 594.0 m; in Sweden--Bodahamnborringen-1, 0.55-0.60 m (Grahn 1981); Tvaren-2, 150.8-152.4 m (see Grahn et al. 1996, fig. 6--can be reworked specimens); in Poland--Proniewicze IG-1, 628.2-631.2 m; Kctrzyn IG-1, 1579.9-1580.4 m.
Conochitina viruana sp. nov. Figure 3
2006 Conochitina sp. 2. Nolvak & Bauert, pl. I, fig. 2.
Derivation of name. From the county name Viru in NE Estonia.
Holotype. GIT 718-4, Fig. 3A, Velise (F-97) core, 209.20-209.28 m, Kukruse RS.
Type locality and horizon. Velise (F-97) drill core, 208.8-209.7 m, Maidla Member, Viivikonna Formation, middle part of the Kukruse RS, lowermost Sandbian.
Dimensions ([micro]m). Holotype: L: 365, Dp: 80, Dc: 55. The biometric data for 36 specimens from the Saare (K-20), Vihterpalu (1103), Kerguta (565) and Bliudziai (150) sections are: L: 256-384, mean 309; Dp: 68-92, mean 80; Dc: 40-71, mean 57.
Diagnosis. Conochitina species with a conspicuous flexure and shoulder, a rounded basal margin and a slightly foveolate vesicle wall surface.
Description. Conochitina viruana has usually a foveolate vesicle wall ornamentation, although rarely smooth specimens are encountered as well. The chamber is cylindrical. The basal margin is rounded. The neck is cylindrical and slightly flaring oralwards. The base is convex and shows two or three concentric ridges around the callus and scar.
Discussion. Conochitina viruana does not have such a well-developed flexure like C. savalaensis. It is distinguished from Conochitina dolosa Laufeld by a much smaller size and a specific foveolate ornamentation. Besides, the vesicle wall of C. dolosa is mostly smooth, the basal margin is rounded and without a flexure. However, transitional forms between C. viruana and C. dolosa do occur and we designated these as cf. viruana (Fig. 3F). Having a limited temporal range in strata overlying C. savalaensis, this species refers to the middle part of the E. rhenana Subzone within the L. stentor chitinozoan Zone (Nolvak & Grahn 1993; Nolvak et al. 2006).
Occurrence. The previously published records of C. viruana are:
Conochitina viruana nom. nud.; Mannil 1986, fig. 2.1.1; Modlinski et al. 2002a, fig. 4.
Conochitina nov. sp. B; Bauert & Bauert 1998, app. 14.
Conochitina sp. 2; Nolvak 1999, app. 6, 2001, app. 8, 2003, app. 23, 2005, app. 27, 2008, app. 6, 2010, app. 6; Saadre et al. 2004, fig. 7; Nolvak & Bauert 2006, pl. I, fig. 2, app. 9; Hints et al. 2014, fig. 2.
Besides the published occurrences, a few hundred specimens have been recorded in strata of the lower Kukruse RS from the following drill core sections: in Estonia--Savala, 14.6-15.5 m; Ohesaare, 480.8 m; Velise (F-97), 209.2 m; Vihterpalu (357), 36.5 m; in Latvia--Aizpute-41, 1064.0 m; Baldone, 867.5 m; Baltinava 701.0 m; in Lithuania--Bliudziai (150), 1377.2-1377.7 m; in Poland--Proniewicze IG-1, 626.2 m.
Subfamily BELONECHITININAE Paris 1981 Genus Belonechitina Jansonius 1964
Belonechitina intonsa sp. nov. Figure 4
2006 Belonechitina wesenbergensis s.l. (Eisenack 1959); Nolvak & Bauert 2006, pl. IV, fig. 9.
Derivation of name. Latin 'intonsus', meaning unshaven, referring to the vesicle ornamentation type.
Holotype. GIT 544-41, Fig. 4A, Kerguta (565) core, 157.1-157.2 m, Maidla Member, Viivikonna Formation, Kukruse RS.
Type locality and horizon. Kerguta (565) core 157.1-159.1 m, Maidla Member, Viivikonna Formation, Kukruse RS, lowermost Sandbian.
Dimensions (pm). Holotype: L: 208; Dp: 67; Dc: 42. The biometric data for 37 specimens from the Saare (K-20), Vihterpalu (1103), Kerguta (565) and Bliudziai (150) sections: L: 160-264, mean 198; Dp: 66-96, mean 76; Dc: 36-64, mean 44.
Diagnosis. Belonechitina species with a cylindrical chamber and a cylindrical neck. The spines are distributed evenly over the entire vesicle surface. The spiny base is mostly convex and provided with a basal callus and scar. The basal margin is sharp.
Description. Belonechitina intonsa has sometimes a subcylindrical chamber, whereas the maximum chamber diameter is observed near the basal margin. The vesicle wall and the base are covered with short simple spines of similar length. In cases of poor preservation (when the spines are removed) it may be difficult to distinguish B. intonsa from C. viruana.
Discussion. The ratio of a chamber length to the neck is mostly around 2: 1, however, in rare cases the neck can be longer than the chamber (Fig. 4C). Sometimes atypical specimens with a concave base are encountered (Fig. 4D). This may be related to poor preservation and the respective findings are designated here as cf. Simple spines may be rather short in some specimens (similar to tubercules) and the flexure may be rather inconspicuous (Fig. 4E). Belonechitina intonsa has some similarities with B. wesenbergensis brevis (Eisenack), however, the latter has a distinctively subconical chamber and has so far been encountered only in considerably younger strata. The overall shape of B. intonsa is similar to B. villosa (Grahn), but the vesicle of the latter species is less ornamented, being covered by fewer and longer spines. It can be distinguished from elongated forms of C. savalaensis by having an ornamentation. Belonechitina intonsa is considerably larger than B. britannica Vandenbroucke (2008) and has mostly a more distinctive shoulder and flexure and shorter spines. The distribution of B. intonsa is limited to the strata of the Kukruse RS.
Occurrence. The previously published records of B. intonsa are:
Belonechitina sp. nov. A; Bauert & Bauert 1998, app. 14.
Belonechitina sp. 1; Modlinski et al. 2002a, fig. 4; Nolvak 2003, app. 23, 2005, app. 27; Saadre et al. 2004, fig. 7.
Belonechitina wesenbergensis s.l.; Nolvak & Bauert 2006, pl. IV, fig. 9.
The other drill cores from where B. intonsa has been recorded in the Kukruse RS strata are: in Estonia--Tartu (453), 336.6 m; Viljandi, 372.3 m; Mannamaa (F-367), 168.1 m; Rapla, 166.5 m; Velise (F-97), 209.2 m; Savala, 22.5 m; Viki, 341.1-342.2 m; Valga (10), 407.8 m; in Latvia--Baldone, 862.3 m; Kandava-25, 934.6 m; in Lithuania--Bliudziai (150), 1376.3-1378.6 m; in Sweden--Tvaren 2, 150.8 m; Grotlingbo, 440.0 m; in Ukraine--Kovel-1, 262.9-271.8 (?275.0) m.
Acknowledgements. The authors would like to thank Heikki Bauert (IG TUT) for help in preparing the figure and SEM photos. We are grateful to O. Hints and J. Verniers for their constructive reviews. This work was supported by the Estonian Research Council grant PUT 378 and ETF9039 and is a contribution to IGCP Project 591.
Jaak Nolvak and Garmen Bauert
Institute of Geology at Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia; firstname.lastname@example.org, email@example.com
Received 16 July 2014, accepted 4 May 2015
Bauert, G. & Bauert, H. 1998. Distribution of chitinozoans in the Tartu (435) core. In Tartu (453) Drill Core (Poldvere, A., ed.), Estonian Geological Sections, 1, App. 14.
Bauert, H. & Kattai, V. 1997. Kukersite oil shale. In Geology and Mineral Resources of Estonia (Raukas, A. & Teedumae, A., eds), pp. 313-327. Estonian Academy Publishers, Tallinn.
Eisenack, A. 1931. Neue Mikrofossilien des baltischen Silurs I. Palaeontologische Zeitschrift, 13, 74-118.
Eisenack, A. 1955. Neue Chitinozoen aus dem Silur des Baltikums und dem Devon der Eifel. Senckenbergiana Lethaea, 36, 311-319.
Eisenack, A. 1959. Neotypen baltischer Silur--Chitinozoen und neue Arten. Neues Jahrbuch fur Geologie und Palaontologie, Abhandlungen, 108, 1-20.
Eisenack, A. 1972. Beitrage zur Chitinozoen-Forschung. Palaeontographica Abt. A, 140, 117-130.
Grahn, Y. 1981. Middle Ordovician Chitinozoa from Oland. Sveriges Geologiska Undersokning, Serie C, 784, 1-51.
Grahn, Y., Nolvak, J. & Paris, F. 1996. Precise chitinozoan dating of Ordovician impact events in Baltoscandia. Journal of Micropalaeontology, 15, 21-35.
Hints, O., Nolvak, J. & Viira, V. 2007. Kukersite oil shale deposits--Middle or Late Ordovician in age? Oil Shale, 24, 527-533.
Hints, O., Martma, T., Mannik, P., Nolvak, J., Poldvere, A., Shen, Y. & Viira, V. 2014. New data on Ordovician stable isotope record and conodont biostratigraphy from the Viki reference drill core, Saaremaa Island, western Estonia. GFF, 136, 100-104.
Jansonius, J. 1964. Morphology and classification of some Chitinozoa. Bulletin of Canadian Petroleum Geology, 12, 901-912.
Laufeld, S. 1974. Silurian Chitinozoa from Gotland. Fossils and Strata, 5, 1-130.
Mannil, R. 1976. Distribution of graptoloids in the Ordovician carbonate rocks of the East Baltic area. In Graptolites and Stratigraphy (Kaljo, D. & Koren, T., eds), pp. 105-118. Akademiya Nauk Estonskoj SSR, Tallinn [in Russian, with English summary].
Mannil, R. 1986. Stratigraphy of the kukersite-bearing beds CIb-CIII. In Geology of the Kukersite-Bearing Beds of the Baltic Oil Shale Basin (Puura, V., ed.), pp. 12-24. Academy of Sciences of the Estonian SSR, Institute of Geology, Valgus Publishers, Tallinn [in Russian, with English summary].
Modlinski, Z., Nolvak, J. & Szymanski, B. 2002a. Zespoly Chitinozoa serii ordowickiej otworu Proniewicze IG 1 (NE Polska) [Chitinozoan biozonation of the Ordovician succession in the borehole Proniewicze IG 1 (NE Poland)]. Przeglqd Geologiczny, 50, 67-74 [in Polish].
Modlinski, Z., Nolvak, J. & Szymanski, B. 2002b. Zespoly Chitinozoa serii ordowickiej otwore Kctrzyn IG 1 (NE Polska) [Chitinozoan biozonation of the Ordovician succession in the borehole Kctrzyn IG 1 (NE Poland)]. Przeglqd Geologiczny, 50, 1149-1158 [in Polish].
Nolvak, J. 1999. Distribution of chitinozoans. In Taga-Roostoja (25 A) Drill Core (Poldvere, A., ed.), Estonian Geological Sections, 2, 10-12, App. 6.
Nolvak, J. 2001. Distribution of chitinozoans. In Valga (10) Drill Core (Poldvere, A., ed.), Estonian Geological Sections, 3, 8-10, App. 8.
Nolvak, J. 2002. Distribution of chitinozoans. In Soovalja (K-1) Drill Core (Poldvere, A., ed.), Estonian Geological Sections, 4, 10-12.
Nolvak, J. 2003. Distribution of Ordovician chitinozoans. In Ruhnu (500) Drill Core (Poldvere, A., ed.), Estonian Geological Sections, 5, 23-25, Apps 22, 23 on CD-R.
Nolvak, J. 2005. Distribution of Ordovician chitinozoans. In Mehikoorma (421) Drill Core (Poldvere, A., ed.), Estonian Geological Sections, 6, 20-22, Apps 26, 27 on CD-R.
Nolvak, J. 2008. Distribution of Ordovician chitinozoans. In Mannamaa (F-367) Drill Core (Poldvere, A., ed.), Estonian Geological Sections, 9, 13-18, App. 6.
Nolvak, J. 2010. Distribution of Ordovician chitinozoans. In Viki Drill Core (Poldvere, A., ed.), Estonian Geological Sections, 10, 17-18, App. 6.
Nolvak, J. & Bauert, G. 2006. Distribution of Ordovician chitinozoans. In Kerguta (565) Drill Core (Poldvere, A., ed.), Estonian Geological Sections, 7, 9-11, Apps 8, 9 on CD-R.
Nolvak, J. & Grahn, Y. 1993. Ordovician chitinozoan zones from Baltoscandia. Review of Palaeobotany and Palynology, 79, 245-269.
Nolvak, J., Hints, O. & Mannik, P. 2006. Ordovician time-scale in Estonia: recent developments. Proceedings of the Estonian Academy of Sciences, Geology, 55, 95-108.
Paris, F. 1981. Les Chitinozoaires dans le Paleozoique du Sud-Ouest de l'Europe. Memoire de la Societe geologique et mineralogique de Bretagne, 26, 1-496.
Paris, F., Grahn, Y., Nestor, V. & Lakova, I. 1999. A revised chitinozoan classification. Journal of Paleontology, 73, 549-570.
Saadre, T., Einasto, R., Nolvak, J. & Stouge, S. 2004. Ordovician stratigraphy of the Kovel-1 well (Volkhov-Haljala) in the Volynia region, northwestern Ukraine. Bulletin of the Geological Survey of Denmark, 51, 47-69.
Umnova, N. I. 1981. Ordovician and Silurian Chitinozoa from the northern part of the Russian platform. Palaeontological Journal, Moscow, 1981, 3, 23-34 [in Russian].
Vandenbroucke, T. R. A. 2008. Upper Ordovician chitinozoans from the British historical type areas and adjacent key sections. Monograph of the Palaeontographical Society, London, 1-113. (Publ. No. 628, part of Vol. 161 for 2007).
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|Author:||Nolvak, Jaak; Bauert, Garmen|
|Publication:||Estonian Journal of Earth Sciences|
|Date:||Sep 1, 2015|
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