Research paper Bio- and magnetostratigraphy of Rupelian–mid Chattian deposits from the Danish land area Katarzyna K. Śliwińska a, ⁎, Niels Abrahamsen a , Claus Beyer b , Thomas Brünings-Hansen c , Erik Thomsen a , Kaare Ulleberg d , Claus Heilmann-Clausen a a Aarhus University, Department of Earth Sciences, Høegh Guldbergs Gade 2, 8000 Aarhus C, Denmark b CB-Magneto, Nørregade 27, 8670 Låsby, Denmark c Miljøministeriet, Naturstyrelsen, Sorsigvej 35, 6760 Ribe, Denmark d Kløverstien 7, 3070 Sande, Norway abstract article info Article history: Received 23 June 2011 Received in revised form 31 December 2011 Accepted 20 January 2012 Available online 30 January 2012 Keywords: dinoflagellate cysts magnetostratigraphy benthic foraminifera calcareous nannofossils Rupelian Chattian The age of the lithostratigraphic units in the Oligocene succession of Denmark is not well known. In order to remedy this situation, an integrated bio-magnetostratigraphical study of the Rupelian–mid Chattian deposits was carried out on six key sections situated in central Jutland. The studied sections include all previously known lithostratigraphical units (i.e., the Grundfør and Viborg Clay Members of the Viborg Formation, Linde Clay, Hvorslev Clay, Branden Clay) and a new, informal Unit X. The biostratigraphical part of the paper critically discusses the differences in ranges of some dinoflagellate cysts in relation to the two most commonly applied dinocyst zonations, the D- and NSO-zonation. The local calcareous nannofossil zonation of the upper NP23–lower NP25 interval in the studied sections is cor- related to the standard NP zonation via the Contessa Barbetti Road section in central Italy. The correlation shows that an interval of the range of the dinoflagellate cyst Svalbardella recognized within the lower Chat- tian Asterigerina guerichi guerichi Zone in Denmark and Belgium is coeval with the global Oi2b cooling event. The identified magnetic polarity intervals have been correlated with the global polarity time scale on the basis of the biostratigraphy. The Viborg Formation is thus referred to Chron C13n and the lowermost part of C12r; the Linde Clay is referred to lower Chron C12r; and the Hvorslev Clay is referred to Chron C11n, C10 and C9r, or only the C11n.1n–C10r interval. The Branden Clay is referred to Chron C9r, C9n and C8r. Unit X is referred to Chron C8n. © 2012 Elsevier B.V. All rights reserved. 1. Introduction More than 100 m thickness of marine Oligocene clays and silts occur in the subsurface of Jutland, western Denmark, and crop out in several localities. Parts of the succession have been known since the beginning of the 20th century from paleontological studies of molluscs from outcrops (Harder, 1913; Ravn, 1907). Subsequent re- search has mainly been based on borehole material and includes sed- imentological, micropaleontological and biostratigraphical studies (chiefly foraminifera) (e.g. Nielsen, 1994). A formal lithostratigraphic mapping of the entire succession has not been established yet, and currently two formations and several informal lithostratigraphic units are in use. Little research has been done since 1995 and the stratigraphy and age of the deposits is still imprecisely known. Age interpretation is hampered by a strong provincialism of the calcareous micro- and nannofossils, due to the paleogeographic setting of Denmark in the semi-enclosed North Sea Basin. A further obstacle for dating the sediments is a lack of good magnetostratigraphic data. A number of regional unconformities in the Danish Oligocene have been suggested (Michelsen et al., 1998), but their ages are not well documented. Seismic stratigraphical studies have shown that Eocene hemipela- gic sediments in the eastern part of the North Sea Basin, including Denmark, at the beginning of the Oligocene were succeeded by pro- grading units of silt and clay sourced from the north and north-east (Michelsen et al., 1998). These authors and others, e.g. Knox et al. (2010), interpreted the shift in depositional style as a result of a sig- nificant Scandinavian uplift. However, this uplift has been disputed by others (e.g. Huuse, 2002; Nielsen et al., 2009) who explained the changes in the sedimentation pattern as a result of climatic change and eustatic lowering of sea level. The global climate cooled considerably at the end of the Eocene, and the Oligocene is the first epoch with a modern icehouse climate. The epoch includes several major events of glaciation on Antarctica associated with eustatic sea level falls (e.g. Pekar et al., 2002). Review of Palaeobotany and Palynology 172 (2012) 48–69 ⁎ Corresponding author. E-mail address: kasia.sliwinska@geo.au.dk (K.K. Śliwińska). 0034-6667/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.revpalbo.2012.01.008 Contents lists available at SciVerse ScienceDirect Review of Palaeobotany and Palynology journal homepage: www.elsevier.com/locate/revpalbo