Abstract
The biostratigraphical data on the East Baltic Silurian chitinozoans are summarized. Based on the study of nine East Baltic drill cores, 28 regional chitinozoan zonal units, including 26 biozones and 2 interzones, are briefly characterized. In comparison with earlier publications, the Silurian chitinozoan biozonation chart is essentially updated, some biozonal units are added, some renamed and several previous subdivisions have been abolished or replaced. The ranges of the stratigraphically most important chitinozoan species throughout the East Baltic Silurian are discussed. Regional chitinozoan biozones are correlated with the global chitinozoan biozones and graptolite biozones, as well as with the regional stratigraphical units of Estonia, Latvia and the Kaliningrad district.
Highlights
The first records of Silurian chitinozoans in Estonia were presented by Eisenack (1970) and Männil (1970)
Regional chitinozoan biozones are correlated with the global chitinozoan biozones and graptolite biozones, as well as with the regional stratigraphical units of Estonia, Latvia and the Kaliningrad district
Continuous study by the present author of East Baltic Silurian chitinozoans from more than 50 outcrops and drill cores has already lasted for 35 years (Nestor 1976–2011)
Summary
The first records of Silurian chitinozoans in Estonia were presented by Eisenack (1970) and Männil (1970). Loydell (graptolites) of the same East Baltic core sections, Aizpute (Loydell et al 2003), Ventspils D-3 (Loydell & Nestor 2005) and Kolka-54 (Loydell et al 2010), enabled more precise correlation of the biozones of these fossil groups in the lower Silurian. The distribution of chitinozoans in the Llandovery and Wenlock beds of the East Baltic drill cores has been treated in many papers (e.g. Nestor 1994), but the exact correlation between the chitinozoan and graptolite biozones is still partly obscure. K. Loydell in the study of some East Baltic drill cores (Aizpute, Ventspils, Kolka) has considerably contributed to integration of these biozones (Loydell et al 2003, 2010; Loydell & Nestor 2005). The present paper deals with the distribution of chitinozoan species in the Kaugatuma, Ruhnu, Ohesaare, Kolka-54, Ventspils D-3, Aizpute-41, Pavilosta, Northern Gusevskaya 1 (Gussev-1, Llandovery–Wenlock) and Dubovskoye (Northern Gusevskaya 2, Ludlow–Přídolí) drill cores (Fig. 1), represented mostly by carbonate and carbonate-argillaceous shelf deposits.
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