Conodonts of the uppermost Uhaku, the Kukruse, and the lower Haljala stages (uppermost Darriwilian and lower Sandbian) of Estonia are discussed. The distribution of conodonts within the Pygodus serra, P. anserinus, and Amorphognathus tvaerensis zones is considered on the basis of 2 outcrop and 15 drill core sections. Judging by the Global Stratotype Section, Fågelsång, Sweden, the base of the Upper Ordovician Series should be lower than the first appearance of A. tvaerensis. The Estonian material shows that elements of A. tvaerensis from the lowermost range of the species are of a morphotype similar to A. inaequalis. It is proposed that the A. inaequalis Subzone be upgraded to the A. inaequalis Zone. The best level for the Middle–Upper Ordovician boundary in Estonia is at the lower boundary of the Kukruse Stage below the appearance of A. tvaerensis and/or A. inaequalis.
Bergström, S. M. 1964. Remarks on some Ordovician conodont faunas from Wales. Acta Universitatis Lundensis, Sectio II, 3, 1–66.
Bergström, S. M. 1971. Conodont biostratigraphy of the Middle and Upper Ordovician of Europe and eastern North America. Geological Society of America Memoir, 127, 83–157.
Bergström, S. M. 1983. Biogeography, evolutionary relationships, and biostratigraphic significance of Ordovician platform conodonts. Fossils and Strata, 15, 35–58.
Bergström, S. M. 2007a. The Ordovician conodont biostratigraphy in the Siljan region, south-central Sweden: a brief review of an international reference standard. In 9th Meeting of the Working Group on Ordovician Geology of Baltoscandia. Field Guide and Abstracts (Ebbestad, J. O. R., Wickström, L. & Högström, A. E. S., eds), SGU Rapporter och meddelanden, 128, 26–41.
Bergström, S. M. 2007b. Middle and Upper Ordovician conodonts from the Fågelsång GSSP, Scania, southern Sweden. Geologiska Föreningens i Stockholm Förhandlingar, 129, 77–82.
Bergström, S. M. & Orchard, M. J. 1985. Conodonts of the Cambrian and Ordovician Systems from the British Isles. In
A Stratigraphical Index of Conodonts (Higgins, A. C. & Austin, R. L., eds), pp. 32–67. Ellis Horwood, Chichester.
Bergström, S. M., Rhodes, F. H. T. & Lindström, M. 1987. Conodont biostratigraphy of the Llanvirn–Llandeilo and Llandeilo–Caradoc Series boundaries in the Ordovician System of Wales and the Welsh Borderland. In Conodonts: Investigative Techniques and Applications (Austin, R. L., ed.), pp. 294–315. Ellis Horwood, Chichester.
Bergström, S. M., Finney, S. C., Chen X., Pålsson, C., Wang, Z. H. & Grahn, Y. 2000. A proposed global boundary stratotype for the base of the Upper Series of the Ordovician System: The Fågelsång section, Scania, southern Sweden. Episodes, 23, 102–109.
Dzik, J. 1976. Remarks on the evolution of Ordovician conodonts. Acta Palaeontologica Polonica, 21, 395–455.
Dzik, J. 1978. Conodont biostratigraphy and paleogeographical relations of the Ordovician Mójcza Limestone (Holy Cross Mts, Poland). Acta Palaeontologica Polonica, 23, 51–72.
Dzik, J. 1994. Conodonts of the Mójcza Limestone. Palaeontologica Polonica, 53, 43–128.
Hints, O., Nõlvak, J. & Viira, V. 2005. Microfossil dynamics and biostratigraphy in the Uhaku–Kukruse boundary interval (Ordovician) of NE Estonia. In The Sixth Baltic Stratigraphical Conference, August 23–25, St. Petersburg, Russia. Abstracts (Koren, T., Evdokimova, I. & Tolmacheva, T., eds), pp. 40–42. St. Petersburg.
Hints, O., Nõlvak, J. & Viira, V. 2007. Kukersite oil shale of Estonia – Middle or Upper Ordovician in age? Oil Shale, 24, 527–533.
Lindström, M., Racheboeuf, P. R. & Henry, J.-L. 1974. Ordovician conodonts from the Postolinnec Formation (Crozon peninsula, massif Armoricain) and their stratigraphic significance. Geologica et Palaeontologica, 8, 15–28.
Männik, P. 2001. Distribution of conodonts. In Valga (10) Drill Core (Põldvere, A., ed.), Estonian Geological Sections, 3, 10–12.
Männik, P. 2003. Distribution of Ordovician and Silurian conodonts. In Ruhnu (500) Drill Core (Põldvere, A., ed.), Estonian Geological Sections, 5, 17–23.
Männik, P. 2007. Recent developments in the Upper Ordovician and lower Silurian conodont biostratigraphy in Estonia. Estonian Journal of Earth Sciences, 56, 35–46.
Männik, P. & Viira, V. 2005. Distribution of Ordovician conodonts. In Mehikoorma (421) Drill Core (Põldvere, A., ed.), Estonian Geological Sections, 6, 16–20.
Männil, R. 1966. Istoriya razvitiya Baltijskogo bassejna v ordovike [Evolution of the Baltic Basin During the Ordovician]. Valgus, Tallinn, 199 pp. [in Russian, with English summary].
Männil, R. 1976. Distribution of graptoloids in the Ordovician carbonate rocks of the East Baltic area. In Graptolityi stratigrafiya [Graptolites and stratigraphy] (Kaljo, D. & Koren, T., eds), pp. 105–118. Institute of Geology, Academy of Sciences
of Estonian SSR, Tallinn [in Russian, with English summary].
Männil, R. 1986. Stratigraphy of kukersite-bearing deposits CIb–CIII. In Stroenie slantsenosnoj tolshchi Pribaltijskogo basseina goryuchikh slantsev-kukersitov [Geology of the kukersite-bearing beds of the Baltic oil shale basin] (Puura, V., ed.), pp. 12–24. Institute of Geology, Academy of Sciences of Estonian SSR, Tallinn [in Russian, with English summary].
Männil, R. & Meidla, T. 1994. The Ordovician System of the East European Platform (Estonia, Latvia, Lithuania, Byelorussia, parts of Russia, the Ukraine and Moldova). In International Union of Geological Sciences Publication, 28, 9–14.
Nõlvak, J. 1997. Ordovician. Introduction. In Geology and Mineral Resources of Estonia (Raukas, A. & Teedumäe, A., eds), p. 52. Estonian Academy Publishers, Tallinn.
Nõlvak, J. & Goldman, D. 2004. Distribution of Nemagraptus in the East Baltic Ordovician. In WOGOGOB-2004 Conference Materials (Hints, O. & Ainsaar, L., eds), pp. 75–76. Tartu University Press.
Nõlvak, J., Hints, O. & Männik, P. 2006. Ordovician timescale in Estonia: recent developments. In Proceedings of the Estonian Academy of Sciences, Geology, 55, 95–108.
Pålsson, C., Månsson, K. & Bergström, S. M. 2002. Biostratigraphical and palaeoecological significance in the Middle–Upper Ordovician Andersö Shale: an unusual ‘mixed facies’ deposit in Jämtland, central Sweden. Transactions of the Royal Society of Edinburgh: Earth Sciences, 93, 35–57.
doi:10.1017/S0263593302000032
Põldvere, A., Meidla, T., Bauert, C., Bauert, H. & Stouge, S. 1998. Ordovician. In Tartu (453) Drill Core (Männik, P., ed.), Estonian Geological Sections, 1, 11–17.
Rhodes, F. H. T. 1953. Some British Lower Palaeozoic conodont faunas. Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences, 237, 647, 261–334.
doi:10.1098/rstb.1953.0005
Viira, V. 1967. Ordovician conodont succession in the Ohesaare core. Eesti NSV Teaduste Akadeemia Toimetised, Keemia, Geoloogia, 16, 319–329 [in Russian, with English summary].
Viira, V. 1974. Konodonty ordovika Pribaltiki [Ordovician conodonts of the East Baltic]. Valgus, Tallinn, 140 pp. [in Russian, with English summary].
Viira, V. & Männik, P. 1999. Distribution of conodonts. In Taga-Roostoja (25A) Drill Core (Põldvere, A., ed.), Estonian Geological Sections, 2, 9–10.
Viira, V., Aldridge, R. J. & Curtis, S. 2006a. Conodonts of the Kiviõli Member, Viivikonna Formation (Upper Ordovician) in the Kohtla section, Estonia. Proceedings of the Estonian Academy of Sciences, Geology, 55, 213–240.
Viira, V., Löfgren, A. & Sjöstrand, L. 2006b. Distribution of Ordovician conodonts. In Kerguta (565) Drill Core (Põldvere, A., ed.), Estonian Geological Sections, 7, 11–13.
