Abstract
Abstract. Species of the fusiform peridiniacean dinoflagellate cyst genera Svalbardella Manum, 1960, emend. (Eocene–Oligocene) and Palaeocystodinium Alberti, 1961 (Late Cretaceous–Miocene), have been examined from the high to middle latitudes of the Northern Hemisphere: Spitsbergen, Norwegian-Greenland Sea, Labrador Sea, western North Atlantic, and the North Sea basin. The genus Svalbardella is emended to comprise species with smooth or finely ornamented surfaces and for which one or both horns are bluntly rounded. Svalbardella clausii sp. nov. has a narrow range restricted to the lowermost Chattian (close to the NP24–NP25 boundary and within Chron C9n), and it therefore appears a useful stratigraphical marker. This species has a wide distribution across the North Atlantic, having been reported from the North Sea basin, western North Atlantic, and the Labrador Sea. Svalbardella clausii sp. nov. overlaps stratigraphically with the reoccurrence interval of Svalbardella cooksoniae Manum, 1960, and spans the Oi-2b cooling maximum. Its presence may therefore be related to the establishment of cooler surface waters at this time. Svalbardella kareniae sp. nov. has a discordant occurrence: Lower Oligocene and Lower Miocene of the Norwegian Sea at Deep Sea Drilling Project Site 338 and Ocean Drilling Program Site 643, respectively, and mid-Oligocene of the North Sea. Its distribution suggests that Svalbardella kareniae sp. nov. favours more open marine conditions. Palaeocystodinium obesum Fensome et al., 2009, described from offshore eastern Canada where it has a highest occurrence in the Lower Oligocene, is emended to include specimens with a finely ornamented periphragm and traces of tabulation in addition to the archeopyle.
Highlights
Even though in the original generic description of Palaeocystodinium the tabulation is expressed by archeopyle alone, several species assigned to this genus show signs of additional tabulation
The present study describes two new species, Svalbardella clausii sp. nov. and Svalbardella kareniae sp. nov., from the Oligocene of the North Atlantic region, and discusses their stratigraphical and palaeoenvironmental significance
Due to the high risk of caving we focus here on the highest occurrences (HOs)
Summary
The fossil dinoflagellate cyst genus Svalbardella Manum, 1960, is known from the Middle Eocene to Oligocene primarily of the Northern Hemisphere: Spitsbergen (Manum, 1960), Western Siberia (Iakovleva, 2011), Greenland (Birkenmajer et al, 2010; Nøhr-Hansen, 2003), the Norwegian-Greenland Sea (Eldrett et al, 2004, 2019; Sliwinska and Heilmann-Clausen, 2011), Arctic Canada (Ioannides, 1986), the North Sea basin (Heilmann-Clausen and Van Simaeys, 2005; Schiøler, 2005; Sliwinska, 2019; Van Simaeys et al, 2005), the western North Atlantic (Egger et al, 2016; Firth et al, 2013; Head and Norris, 1989), and the Paratethys (e.g. Pross et al, 2010). Only two species are formally assigned to this genus, Svalbardella cooksoniae Manum, 1960, and Svalbardella partimtabulata Heilmann-Clausen and Van Simaeys, 2005. J. Head: New species of the dinoflagellate cyst genus Svalbardella Manum, 1960 terval within the Middle Eocene (Chron C18r–C18n; midBartonian; Heilmann-Clausen and Van Simaeys, 2005; Sliwinska et al, 2016; Thomsen et al, 2012) of Denmark. In the Oligocene succession of the North Sea basin, the Norwegian-Greenland Sea, and the Paratethys, Svalbardella cooksoniae occurs in several discrete intervals Three of these intervals are synchronous with Oligocene cooling maxima (Sliwinska, 2019; Sliwinska and Heilmann-Clausen, 2011; Van Simaeys et al, 2005). Regarding Palaeocystodinium minor Strauss in Strauss et al, 2001, specimens “may display very faint longitudinal parasutural ledges at the horn bases” (Strauss et al, 2001, p. 407)
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