The Sub-Boreal/Boreal ammonite succession at the Oxfordian/Kimmeridgian boundary at Flodigarry, Staffin Bay (Isle of Skye), Scotland

Abstract

This paper describes extensive new collections of ammonites made bed-by-bed across the Oxfordian/Kimmeridgian boundary sequence in the Flodigarry sections at Staffin Bay on the Isle of Skye. The ammonites belong to the Sub-Boreal family Aulacostephanidae and the Boreal family Cardioceratidae, enabling recognition of both the current standard Sub-Boreal and Boreal ammonite zonations. In consequence, it is possible to make a close correlation of these two zonal schemes through the interval studied in Skye. The research has provided new palaeontological data at levels of precision that justify the proposal of the section at Staffin as the site of a potential Global Boundary Stratotype Section and Point (GSSP) for the Oxfordian/Kimmeridgian boundary.The traditional Oxfordian/Kimmeridgian boundary placed at the Pseudocordata/Baylei zonal boundary of the Sub-Boreal zonal scheme corresponds precisely to the Rosenkrantzi/Bauhini zonal boundary of the Boreal zonal scheme. This level is characterised by the appearance of the first Pictonia (Pictonia flodigarriensis sp. nov.) together with first Prorasenia, replacing an older assemblage of Ringsteadia–Microbiplices (Sub-Boreal). It is also characterised by the first occurrence of small-sized Amoeboceras (Plasmatites) spp., as well as large Amoeboceras schulginae Mesezhnikov (Boreal). An alternative level that may be considered as a potential GSSP is the boundary between the Bauhini Zone and the Kitchini Zone of the Boreal zonal scheme, characterised by first occurrence of Amoeboceras (Amoebites) of the A. bayi group. This level corresponds to the Planula/Galar subzonal boundary of the Sub-Mediterranean zonal scheme, and lies close to the currently accepted Oxfordian/Kimmeridgian boundary in the Sub-Mediterranean Province.

Ichthyosaurs from the Jurassic of Skye, Scotland

“…Ammonite zones from both the Boreal and sub-Boreal provinces are included in this scheme and, subsequently, the scheme cannot be solely attributed to either of these provincial zonal schemes. This is particularly appropriate for the Upper Jurassic of Skye where Oxfordian and Kimmeridgian ammonites represent both provinces (Matyja et al 2005).…”

Timing of sea level, tectonics and climate events during the uppermost Oxfordian (Planula zone) on the Iberian ramp (northeast Spain)

“…3). The Planula Zone, traditionally assigned to the Upper Oxfordian, is considered to be coeval with the lowermost Kimmeridgian of the Boreal province (Matyja et al, 2006in Gradstein et al, 2012 (Fig. 2).…”

The systematics and paleobiogeographic significance of Sub-Boreal and Boreal ammonites (Aulacostephanidae and Cardioceratidae) from the Upper Jurassic of the Bohemian Massif

“…Prorasenia, Eurasenia, and Rasenioides) found in the Bohemian Massif belong to SubBoreal ammonites. Rasenia has a relatively broad geographical range, covering Greenland, Spitsbergen, the Norwegian Sea, Franz Josef Land, western Siberia, northern Siberia, Great Britain, France, Germany, Poland, Russian Platform, British Columbia and Arctic Canada (Tornquist 1896;Schneid 1940;Birkelund et al 1978Birkelund et al , 1983Callomon & Birkelund 1980;Mesezhnikov 1984;Birkelund & Callomon 1985;Matyja et al 2006;Wierzbowski et al 2010). Therefore, aulacostephanids from northern Bohemia and Saxony thus seem to have a close relationship with ammonites representing the Sub-Mediterranean branch frequently occurring in southern Germany and Poland.…”

“…The Cardioceratid genus Amoeboceras was described from the Barents Sea, the Norwegian Sea shelf, Spitsbergen, western Siberia, northern Siberia, Russian Platform, and East Greenland, (Sykes & Callomon 1979;Birkelund & Callomon 1985;Wierzbowski & Smelror 1993;Meledina 2006;Rogov & Wierzbowski 2009;Glowniak et al 2010;Rogov 2010), as well as from Scotland, northern and central Poland, southern Germany, and Switzerland (Matyja & Wierzbowski 1994Schweigert & Callomon 1997;Gygi 2000;Matyja et al 2006;Wierzbowski et al 2010). The occurrence of Amoeboceras in northern Bohemia corresponds to the equatorward migration of Boreal ammonites close to the Oxfordian/Kimmeridgian boundary.…”