Ammonite and dinoflagellate cyst succession of an Upper Oxfordian - Kimmeridgian black shale core from the Nordkapp Basin, southern Barents Sea

Abstract

The drilling core 7227/8-U-3 located at 72°19'05.655"N 27°33'37.635"E in the southern Barents Sea (Figs. 1 and 2) has revealed a fairly complete succession of species of the ammonite genus Amoeboceras which enables the identification of the standard Boreal ammonite zones, and some informal ammonite horizons of the Upper Oxfordian and Kimmeridgian, well established in East Greenland. The dinoflagellate cyst assemblages in the same core are dominated by seven long-ranging species. Less common are Scriniodinium crystallinum and Scriniodinium galeritum which occur relatively consistently up into the A. regulare Zone, where they seem to disappear. The last representatives of Rhynchodiniopsis cladophora have been found in the A. decipiens and A. elegans horizon corresponding to the A. eudoxus Zone, from where this taxon via transitional forms may evolve into the Cribroperidinium sarjeantii group. Zusammenfassun g. Kern 7227/8-U-3 (72°19'05.655"N, 27°33'37.635"E) aus der siidlichen Barentssee (Abb. 1 und 2) enthalt eine ziemlich komplette Artenfolge des Ammoniten-Genus Amoeboceras. Dies ermiiglicht die Identifizierung der iiblichen borealen Ammonitenzonen und einiger informeller Ammoni tenhorizonte des Oberen Oxfordiums und Kimmeridgiums, die in Ostgriinland gut etabliert sind. In den Dinoflagellatenzysten-Vergesellschaftungen dieses Kerns herrschen sieben Arten vor, deren geologisches Auftreten sich iiber langere Zeitraume erstreckte. Weniger haufig sind Scriniodinium crystallinum und Scriniodinium galeritum, welche relativ zusammenhangend bis hinauf in die A. regulare-Zone vorkom men, dort jedoch anscheinend verschwinden. Die letzten Vertreter von Rhynchodiniopsis cladophora wurden in dem Horizont A. decipiens und A. elegans gefunden, die der A. eudoxus-Zone entsprechen. Von dort aus hat sich dieses Taxon miiglicherweise iiber intermediare Formen zur Cribroperidinium sarjeantii-Gruppe weiterentwickelt.

The Jurassic dinoflagellate cyst zonation of Subboreal Northwest Europe

“…Lentin & Williams (1980) established that high relief cyst surfaces and processes are a flotation adaptation necessary in warm water (the specific gravity of water is 1.00000 at 4°C, falling to 0.99567 at 30°C). This palaeoecological trend in the Jurassic was noted by Wierzbowski & Århus (1990), Smelror (1993) and Riding & Ioannides (1996); these authors found that complex process-bearing forms are more common in the Middle-Upper Jurassic of the Tethyan Realm compared to the Boreal Realm.…”

Biotic Responses to the Mjølnir Meteorite Impact, Barents Sea: Evidence from a Core Drilled within the Crater

“…The Hekkingen Formation on the Barents Shelf is correlative with the Agardhfjellet Formation (late Jurassic age) on Svalbard , Nøttvedt et al 1993) and its marine fossil assemblages closely resemble those described from the Agardhfjellet Formation (Nagy and Basov 1998, Nagy et al 1988, Smelror and Below 1993, Smelror et al 2001b, Wierzbowski and Århus 1990. There are no indications of any significant biotic extinctions associated with the Mjølnir impact (Bremer et al 2001).…”

Ammonites and dinoflagellate cysts in the Upper Oxfordian and Kimmeridgian of the northeastern Norwegian Sea (Nordland VII offshore area): biostratigraphical and biogeographical significance

“…This is partly due to the low species diversity in the deposits, and partly to the fact that most of the recovered species are long-ranging and not particularly useful for detailed biostratigraphic subdivision of the sedimentary sequences. Endemic Boreal species are few and are, as pointed out by WIERZBOWSKI & ÄRHUS (1990), scarce in most areas, or long-ranging.…”

“…A well documented correlation between the Upper Jurassic ammonite zones and the dinoflagellate cyst biostratigraphy allows a more secure age-determination of the strata drilled by exploration wells. Previous studies have shown that the Upper Jurassic dinoflagellate cyst assemblages from the Barents Shelf and Svalbard (WIERZBOWSKI & ÄRHUS 1990, SMELROR et al 1998 differ significantly from those found in the Subboreal areas, and that the dinoflagellate cyst zonations defined for Britain and the North Sea (RIDING & THOMAS 1992) cannot be applied directly to the contemporaneous succession in the Boreal Province. In this respect, the present paper focused on providing new information from an "under-explored" geographic area, and a discussion of the observed differences in the characters of the Upper Oxfordian-Kimmeridgian Boreal and Subboreal dinoflagellate cyst assemblages.…”