GEUS Bulletin no 5.pmd
GEUS Bulletin no 5.pmd GEUS Bulletin no 5.pmd
98 GEUS Bulletin no 5.pmd 98 29-10-2004, 11:14
Jurassic dinoflagellate cyst stratigraphy of Store Koldewey, North-East Greenland Stefan Piasecki, John H. Callomon and Lars Stemmerik The Jurassic of Store Koldewey comprises a Middle Jurassic succession towards the south and an Upper Jurassic succession towards the north. Both successions onlap crystalline basement and coarse sediments dominate. Three main lithostratigraphical units are recognised: the Pelion Formation, including the Spath Plateau Member, the Payer Dal Formation and the Bernbjerg Formation. Rich marine macrofaunas include Boreal ammonites and the successions are dated as Late Bathonian – Early Callovian and Late Oxfordian – Early Kimmeridgian on the basis of new collections combined with material in earlier collections. Fine-grained horizons and units have been analysed for dinoflagellate cysts and the stratigraphy of the diverse and well-preserved flora has been integrated with the Boreal ammonite stratigraphy. The dinoflagellate floras correlate with contemporaneous floras from Milne Land, Jameson Land and Hold with Hope farther to the south in East Greenland, and with Peary Land in North Greenland and Svalbard towards the north. The Middle Jurassic flora shows local variations in East Greenland whereas the Upper Jurassic flora gradually changes northwards in East Greenland. A Boreal flora occurs in Peary Land and Svalbard. The characteristic and stratigraphically important species Perisseiasphaeridium pannosum and Oligosphaeridium patulum have their northernmost occurrence on Store Koldewey, whereas Taeniophora iunctispina and Adnatosphaeridium sp. extend as far north as Peary Land. Assemblages of dinoflagellate cysts are used to characterise significant regional flooding events and extensive sequence stratigraphic units. Keywords: ammonites, Boreal, dinoflagellate cysts, Jurassic, North-East Greenland, Store Koldewey S.P. & L.S., Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: sp@geus.dk J.H.C., Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK. Jurassic sediments are well exposed in the East Greenland Basin from Milne Land (70°N) in the south to Hochstetter Forland (75°N) in the north. Yet farther to the north, Jurassic sediments are restricted to isolated outliers (Ravn 1911; Stemmerik & Piasecki 1990) until the more extensive outcrops of Jurassic deposits in the Wandel Sea Basin in eastern North Greenland are reached (81°N–83°N; Fig. 1). The geographical gap between the Jurassic outcrops of the Wandel Sea Basin (Peary Land) and the well-studied ones of the East Greenland Basin corresponds to the zone covering the transition from the strictly Boreal dinoflagellate cyst flora of Peary Land to the Subboreal hybrid flora of Geological Survey of Denmark and Greenland Bulletin 5, 99–112 © GEUS, 2004 GEUS Bulletin no 5.pmd 99 29-10-2004, 11:14 East Greenland. Accordingly, dinoflagellate data from Store Koldewey are important since they improve correlation between these two floral provinces. The Jurassic exposures on the island of Store Koldewey are also stratigraphically important because they provide the nearest accessible record in guiding the evaluation of the hydrocarbon potential of the extensive offshore shelf areas in the northern region. The Mesozoic of Store Koldewey was first described by Ravn (1911) and Koch (1929) on the basis of data collected by members of ‘Danmarks Expeditionen’ in 1906–1908. Store Koldewey was then not visited by geologists until the summer of 1989, when several field- 99
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<strong>GEUS</strong> <strong>Bulletin</strong> <strong>no</strong> <strong>5.pmd</strong> 98<br />
29-10-2004, 11:14
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