Swedish Ordovician Chitinozoa and biostratigraphy: a review and new data
Grahn, Yngve;Nólvak, Jaak
published: Jul 5, 2010
At least two composite facies belts are known from the Ordovician of Sweden. The Central Baltoscandian Confacies Belt covers Ordovician outcrop areas on Swedish territory, except for the province of Skåne and the western part of the province of Västergötland (Halleberg-Hunneberg district), which are situated in the Scanian Lithofacies Belt. Submarine occurrence of Ordovician rocks within the Central Baltoscandian Confacies Belt are also known from the South Bothnian Sea and the central and southern part of the Baltic Sea. Previously published Ordovician chitinozoan information from this part of Sweden is reviewed and updated, and completed with data from Skåne. Additional new data from Sweden are presented. Characteristic Baltoscandian chitinozoan faunas are known from upper Tremadocian to Hirnantian (upper Ashgill), with an influx of east Gondwana faunas (Australian) in the earliest Darriwilian. In Sweden, the pre-Darriwilian Lagenochitina esthonica Zone partly replaces the Baltoscandian Cyathochitina primitiva Zone, and an interzone replaces the upper Katian and lower Hirnantian Conochitina rugata, Belonechitina gamachiana, and Spinachitina taugourdeaui zones. At present the Angochitina curvata Zone and the Conochitina tuberculata and Ancyrochitina n. sp. 1 subzones in the Baltoscandian biozonation cannot be defined in Swedish strata. Two species, Belonechitina jaanussonii and Cyathochitina giraffa, are described as new. Altogether one hundred and six species, of which thirty-one are in open nomenclature, from twenty-one genera have been recognized from Swedish Ordovician strata.