Geological Survey of Denmark and Greenland Bulletin 12, 1-16 1 GEOLOGICAL SURVEY OF DENMARK AND GREENLAND BULLETIN 12 · 2007 Lithostratigraphy of the Palaeogene – Lower Neogene succession of the Danish North Sea Poul Schiøler, Jan Andsbjerg, Ole R. Clausen, Gregers Dam, Karen Dybkjær, Lars Hamberg, Claus Heilmann-Clausen, Erik P. Johannessen, Lars E. Kristensen, Iain Prince and Jan A. Rasmussen GEOLOGICAL SURVEY OF DENMARK AND GREENLAND DANISH MINISTRY OF THE ENVIRONMENT 2 Geological Survey of Denmark and Greenland Bulletin 12 Keywords Lithostratigraphy, biostratigraphy, North Sea Basin, Palaeogene, Neogene. Cover Complex fabric created by multiple small-scale sand intrusions (light) into dark mudstones – such enigmatic fabrics are commonly associated with the sand-rich units of the Rogaland Group in the Siri Canyon area, offshore Denmark. The illustrated section of core is about 10 cm across and is from the lower Tyr Member (Lista Formation) in the Cecilie-1B well (2346.8 m). Photograph: Jakob Lautrup. Chief editor of this series: Adam A. Garde Editorial board of this series: John A. Korstgård, Geological Institute, University of Aarhus; Minik Rosing, Geological Museum, University of Copenhagen; Finn Surlyk, Department of Geography and Geology, University of Copenhagen Scientific editors of this volume: Jon R. Ineson and Martin Sønderholm Editorial secretaries: Jane Holst and Esben W. Glendal Referees: Paul van Veen (Norway) and Robert O’B. Knox (UK) Illustrations: Stefan Sølberg Digital photographic work: Benny M. Schark Graphic production: Knud Gr@phic Consult, Odense, Denmark Printers: Schultz Grafisk, Albertslund, Denmark Manuscript received: 29 August 2005 Final version approved: 8 September 2006 Printed: 29 June 2007 ISSN 1604-8156 ISBN 978-87-7871-196-0 Geological Survey of Denmark and Greenland Bulletin The series Geological Survey of Denmark and Greenland Bulletin replaces Geology of Denmark Survey Bulletin and Geology of Greenland Survey Bulletin. Citation of the name of this series It is recommended that the name of this series is cited in full, viz. Geological Survey of Denmark and Greenland Bulletin. If abbreviation of this volume is necessary, the following form is suggested: Geol. Surv. Den. Green. Bull. 12, 77 pp. Available from Geological Survey of Denmark and Greenland (GEUS) Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Phone: +45 38 14 20 00, fax: +45 38 14 20 50, e-mail: geus@geus.dk and Geografforlaget A/S Filosofgangen 24, 1., DK-5000 Odense C, Denmark Phone: +45 63 44 16 83, fax: +45 63 44 16 97, e-mail: go@geografforlaget.dk or at www.geus.dk/publications/bull © De Nationale Geologiske Undersøgelser for Danmark og Grønland (GEUS), 2007 For the full text of the GEUS copyright clause, please refer to www.geus.dk/publications/bull 3 Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Geological setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Previous work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Material and methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Offshore and onshore lithostratigraphic nomenclature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Chronostratigraphy and biostratigraphy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Paleocene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Eocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Oligocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Miocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Lithostratigraphy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Rogaland Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Våle Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Bor Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Lista Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Vile Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Tyr Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Ve Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Idun Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Bue Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Rind Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Sele Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Kolga Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Fur Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Balder Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Stronsay Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Horda Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Hefring Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Westray Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Lark Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Dufa Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Freja Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 4 5 Abstract Schiøler, P., Andsbjerg, J., Clausen, O.R., Dam, G., Dybkjær, K., Hamberg, L., Heilmann-Clausen, C., Johannessen, E.P., Kristensen, L.E., Prince, I. & Rasmussen, J.A. 2007: Lithostratigraphy of the Palaeogene – Lower Neogene succession of the Danish North Sea. Geological Survey of Denmark and Greenland Bulletin 12, 77 pp. + 5 plates. As a result of a lithological, sedimentological and biostratigraphic study of well sections from the Danish sector of the North Sea, including some recently drilled exploration wells on the Ringkøbing– Fyn High, the lithostratigraphic framework for the siliciclastic Palaeogene to Lower Neogene sedi- ments of the Danish sector of the North Sea is revised. The sediment package from the top of the Chalk Group to the base of the Nordland Group is subdivided into seven formations containing eleven new members. The existing Våle, Lista, Sele, Fur, Balder, Horda and Lark Formations of previ- ously published lithostratigraphic schemes are adequate for a subdivision of the Danish sector at formation level. Bor is a new sandstone member of the Våle Formation. The Lista Formation is subdivided into three new mudstone members: Vile, Ve and Bue, and three new sandstone members: Tyr, Idun and Rind. Kolga is a new sandstone member of the Sele Formation. Hefring is a new sandstone member of the Horda Formation. Freja and Dufa are two new sandstone members of the Lark Formation. Danish reference sections are established for the formations, and the descriptions of their lithology, biostratigraphy, age and palaeoenvironmental setting are updated. __________________________________________________________________________________________________________ Authors’ addresses P.S.*, J.A., K.D. & L.E.K., Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. * Present address: GNS Science, 1 Fairway Drive, Avalon, P.O. Box 30368, Lower Hutt, New Zealand. E-mail: p.schioler@gns.cri.nz O.R.C. & C.H.-C., Department of Earth Sciences, University of Aarhus, Høegh-Guldbergsgade 2, DK-8000 Århus C, Denmark. G.D. & L.H., DONG Energy, Agern Allé 24–26, DK-2970 Hørsholm, Denmark. I.P. & E.P.J., Statoil Norway, Forusbeen 50, N-4035 Stavanger, Norway. J.A.R., Geological Museum, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark. 6 Fig. 50 Fig . 56 a F ig. 49 Fig. 56b Fig. 61 Fig. 58 Saxo-1 Wessel-1 Tordenskjold-1 Eg-1 Diamant-1 Bertel-1 Mona-1 Karl-1 W. Lulu-3,-1 Cleo-1 Augusta-1 Amalie-1 Tabita-1 Gulnare-1 Gwen-2 Iris-1 Baron-2 Nora-1 Elin-1W-1 Ravn-1 Falk-1 U-1 E-8 Tove-1 John-Flanke-1 Alma-1 Emma-1 Edna-1 Roxanne-1 Ugle-1 Frida-1 L-1 Francisca-1 Cecilie-1 Connie-1 Elna-1 Siri-2 Siri-3 Sofie-1 Floki-1 Sandra-1 Nolde-1 Nini-1 Nini-2 Nini-3 D-1 Vanessa-1 Ibenholt-1 Ida-1 R-1 C-1 K-1 F-1 Inez-1 S-1 Siri-1 V-1 G-1 Deep-Adda-1 Adda-2,-1Bo-1 North-Jens-1 Lulu-1 Lulu-2 Sten-1 Gert-1 Kim-1 Lone-1 57°00' 4°00' 6°00' 56°00' 25 km 250 km C offee Soil Fault North Sea Denmark N S UK G NL P Sir i C an yo n Mid North Sea High Central Graben a b Norwegian–Danish Basin C entral G raben 100 km North Polish Strait East Shetland Platform Fennoscandian Shield Scottish High V ik in g G ra be n Rhenish Massif Bohemian Massif Jylland Sjælland Storebælt Moray Firth Mid North Sea High Ringkøbing–FynHigh Fig. 1. Location maps showing the position of wells used in the study (a) and major structural elements in the greater North Sea area (b) mentioned in the text. On the well map (a) are indicated the locations of the seismic sections shown in Figs 49, 50, 56, 58 and 61. Grey shading on this map indicates the margins of the Siri Canyon; grey shading inside the canyon indicates an area of positive relief within the canyon. GGGGG, Germany; NNNNN, Norway; N LN LN LN LN L, Netherlands; PPPPP, Poland; SSSSS, Sweden; U KU KU KU KU K, United Kingdom. 7 Introduction Intense drilling activity following the discovery of the Siri Field in 1995 has resulted in an improved understanding of the siliciclastic Palaeogene sediment package in the Danish sector of the North Sea (Fig. 1). Many of the new wells were drilled in the search for oil reservoirs in sandstone bodies of Paleocene–Eocene age. The existing lithostrati- graphy was established on the basis of data from a gener- ation of wells that were drilled with deeper stratigraphic targets, with little or no interest in the overlying Palaeo- gene sedimentary succession. This means that this early scheme does not include Palaeogene sandstone units in the Danish sector. In order to improve the understanding of the distribution, morphology and age of the Palaeo- gene sediments, in particular the economically important sandstone bodies, a detailed study of this succession in the Danish sector has been carried out. The main aim was to update the lithostratigraphic framework of the succession on the basis of new data from recently drilled wells. All of the widespread Palaeogene mudstone units in the North Sea were established with Norwegian or Unit- ed Kingdom (UK) type wells. In the present work, these units have been maintained unchanged or with only slight modifications. Danish reference wells have been established for the units, however, and lithological descriptions have been expanded to cover the characteristics of these units in the Danish sector. Many of the sandstone bodies recently discovered in the Danish sector have a limited spatial distribution and are derived from sources different from those of most of the contemporaneous sandstone bodies in the Norwegian and UK sectors; furthermore, the Danish sandstone bodies probably neither overlap nor are in contact with the Nor- wegian/UK sandstones. These units have therefore been established as new in the Danish sector, and have been assigned Danish type and reference sections. The lithostratigraphy presented herein (Fig. 2) has its base at the top of the Early Paleocene (Danian) Ekofisk Formation (Chalk Group). The top of the study section is at the unconformity between the Late Eocene – Mid-Mio- cene Westray Group and the Mid-Miocene to Recent Nordland Group. Oil companies operating in the North Sea have collec- ted a substantial amount of lithostratigraphic data on the Palaeogene successions and a detailed lithostratigraphy has been developed for the Danish and Norwegian sectors (see e.g. Hamberg et al. 2005). A number of informal litho- stratigraphic units have been introduced that have subse- quently found their way into academia and geological survey organisations. It has been the aim of the present work formally to define these new units. This has been done maintaining their original (albeit informal) names whenever feasible. It has not been the aim of this work to provide a se- quence stratigraphic model for the Palaeogene sediments in the central and eastern North Sea; for this the reader is referred to Michelsen et al. (1992, 1995, 1998), Mudge & Bujak (1994, 1996a, b), Neal et al. (1994) and Dan- ielsen et al. (1997). The present contribution does not attempt to review the petroleum-related aspects of the Palaeogene succession. Information about this may be found elsewhere, for example in the annual reports from the Danish Energy Authority. Preliminary results from the present work, including a revised lithostratigraphic scheme, were previously pub- lished in a brief review paper (Schiøler et al. 2005). The present contribution formally describes the new strati- graphic units suggested in the review paper and further documents the Palaeogene – Lower Neogene lithostrati- graphy in the Danish sector of the North Sea. 8 Danian Selandian Thanetian Sparnacian Ypresian Lutetian Ma M id dl e Eo ce ne Lo w er E o ce ne U pp er P al eo ce ne C ha lk G ro up R o ga la nd G ro up St ro ns ay G ro up W es tr ay G ro up St ro ns ay G ro up Lo w er P al eo ce ne Priabonian Rupelian Chattian Aquitanian Burdigalian Langhian Serravallian 15 20 25 30 35 45 50 55 60 65 M id dl e M io ce ne Lo w er M io ce ne Lo w er N eo ge ne Pa la eo ge ne Pa la eo ge ne U pp er O lig o ce ne Lo w er O lig o ce ne U pp er E o ce ne M id dl e Eo ce ne Lillebælt Clay Fm Horda Fm Røsnæs Clay Fm Fur Fm F Ølst Fm Stolle Klint Clay Øster- rende Clay Holmehus Fm Ve Mb Bue Mb RindMb Æbelø Fm Danian Lime- stone Ekofisk Fm Våle Fm Li st a Fo rm at io n Vile Mb Sele Fm Balder Fm Bartonian Lutetian 40 Søvind Marl Fm Søvind Marl Fm Viborg Fm Linde Clay Branden Clay Vejle Fjord Fm Hodde Fm Gram Fm Lark Fm (undivided) Horda Fm Se ri es Sy st em St ag e D en m ar k o ns ho reDanish North Sea Kolga Mb Hef- ring Mb Tyr Mb Bor Mb 49.0 55.5 54.5 57.9 60.0 41.3 37.0 33.7 28.5 23.8 20.5 16.4 14.8 Dufa Mb Odderup Fm Bastrup Sand Ribe Fm Freja Mb Idun Mb N o rd la nd G ro up Arnum Fm Kerteminde Marl Lellinge Greensand 9 Geological setting The Danish sector of the North Sea is situated in the cen- tral and eastern North Sea and comprises three major struc- tural elements: the Central Graben, the Norwegian–Dan- ish Basin (the eastern part of the northern North Sea Ba- sin of Rhys 1974) and the Ringkøbing–Fyn High (Fig. 1; the geographic terminology and names of structural ele- ments in the North Sea used herein are adapted from Rhys 1974, Rønnevik et al. 1975, Deegan & Scull 1977 and Fyfe et al. 2003). The western boundary of the Danish sector largely coincides with the eastern boundary of the Mid North Sea High, the southern boundary largely co- incides with the southern limit of the Ringkøbing–Fyn High, and the northern boundary is in the Norwegian– Danish Basin. This basin as well as the Ringkøbing–Fyn High are Early Permian structures. Active rifting occurred in the Central Graben from the Middle to Late Jurassic along pre-established Palaeozoic fault trends. Major tec- tonic activity around the Palaeozoic and Jurassic struc- tures had largely ceased by Late Cretaceous time, and the sediment basin below the central North Sea was largely characterised by regional subsidence (Ziegler 1981). During the Late Cretaceous to Danian sea-level high, pe- lagic chalk sediments draped the structural highs and the northern and southern North Sea Basins became one North Sea Basin delimited by the Fennoscandian Shield to the north-east, the Rheinish–Bohemian Massif to the south and the British massifs, highs and platforms to the west (see Ziegler 1981 fig. 16 for details). Chalk sedimen- tation continued through to the end of the Danian Stage when it gave way to hemipelagic and siliciclastic sedimen- tation. This was probably caused by uplift of the basin margins to the west and east (Ahmadi et al. 2003). How- ever, most of the siliciclastic sediments were derived from the Scottish High and the East Shetland Platform, uplift- ed by the Iceland plume (Ahmadi et al. 2003). By the time of peak uplift, in the mid-Thanetian, large sand systems were building out towards the central North Sea. Most sediment came from the west, but the Siri Canyon system, a depression in the top chalk surface, was fed from the Fennoscandian Shield in the north-east and north (Fig 1; Ahmadi et al. 2003; Hamberg et al. 2005). Thermal subsidence centered above the Central Graben continued through the Eocene as sea level fell and the temperature decreased. Shallow-marine sediments char- acterised the margins of the North Sea Basin, especially its western margin, whereas basinal mudstone continued to accumulate in the basin centre and in the eastern part of the basin (Joy 1996). Inversions controlled by com- pression between the Atlantic spreading zone to the north- west and the orogenesis of the Alps to the south added to further uplift of the basin margins and submarine fans and turbidites were deposited near the centre of the basin (Jones et al. 2003). During the Oligocene, the North Sea Basin became part of a larger NW European basin. Connection with the North Atlantic broadened and enhanced communi- cation with the oceanic water mass to the north-west, whereas the connection to the south through the North Polish Strait became closed for the deep water (Fyfe et al. 2003). Glacio-eustatic sea-level changes became more fre- quent and controlled the sedimentary cycles. The east- ward progradation direction of the Paleocene and Eocene sediments gave way to sediment supply from the Euro- pean massifs to the far south (Fyfe et al. 2003). Continu- ed subsidence above the Mesozoic rift structures created accommodation space for thick sediment packages of basi- nal mudstones, and few sandstone units reached the basin depocentre above the Mesozoic rifts (Fyfe et al. 2003). In the Neogene Epoch, sediment started to be derived from the Fennoscandian Shield to the north, and the prograda- tion direction changed to the south-west and west in the Danish sector of the North Sea. Facing page: Fig. 2. Lithostratigraphic column for the Palaeogene and Lower Neo- gene of the Danish North Sea sector showing the approximate corre- lation with Danish onshore stratigraphic units. Timescale from Hard- enbol et al. (1998), except for the age of the Paleocene–Eocene bound- ary, which is adapted from Berggren & Aubry (1996) and the age of the Sparnacian–Ypresian boundary, which is from Aubry et al. (2003). Stratigraphy and ages of pre-Chatian onshore lithostratigraphic units are based on Heilmann-Clausen (1995) and Clemmensen & Thom- sen (2005). Post-Rupelian onshore stratigraphy and ages are from Dybkjær & Rasmussen (2000) and Rasmussen (2004a). F, Fur For- mation. 10 Previous work The Permian to Recent lithostratigraphy of the North Sea was described in two pioneering stratigraphic works. Rhys (1974) provided an overview of the structural elements of the North Sea and gave a brief description of the Palaeo- gene sediments. Deegan & Scull (1977) compiled a de- tailed lithostratigraphic subdivision and lithological de- scription for the central and northern North Sea (Figs 3, 4). They subdivided the siliciclastic Palaeogene, Neogene and Quaternary sediments into five major groups: the Montrose, Moray, Rogaland, Hordaland and Nordland Groups. The Montrose and Moray Groups established for the Outer Moray Firth – Forties area are proximal equiv- alents to the Rogaland Group and are not present in the Danish sector, whereas the Rogaland, Hordaland and Nordland Groups have widespread distribution in the Danish sector. The succession of major mudstone forma- tions contained within the three basinwide groups has formed the backbone of all subsequent lithostratigraphic schemes for the central and northern North Sea, includ- ing that of the present contribution. The post-Danian Cainozoic succession of the Danish Central Graben was divided into seven informal units by Kristoffersen & Bang (1982). The Palaeogene comprised five units: North Sea Marl and CEN-1–4 (Fig. 4). The ranks of the units were not stated. Although descriptions and interpretation of the CEN units were detailed, they are essentially informal and have been little used. A revised lithostratigraphy for the Palaeogene and Ne- ogene of the Norwegian North Sea sector was published by Hardt et al. (1989). Their lithostratigraphic scheme includes a number of new Palaeogene and Neogene sand- stone bodies observed in the Norwegian and British sec- tors of the North Sea (Fig. 4). Some of the names of the new sandstone units established by Hardt et al. (1989) were subsequently used informally for comparable sand- stone units discovered in the Danish sector. Mudge & Copestake (1992a, b) presented a revised Palaeogene stratigraphy for the Outer Moray Firth and northern North Sea Basins. In their papers they redefined the Moray and Montrose Groups of Deegan & Scull (1977) and abandoned the Rogaland Group. The authors also demoted the previously established sandstone forma- tions within the two former groups to the rank of mem- bers. Besides, in an innovative approach they allowed for a greater influence of biostratigraphic data on the charac- terisation of the various lithostratigraphic units, an ap- proach which is also followed herein. Knox & Holloway (1992) updated the lithostratigra- phic scheme for the Palaeogene in the British and Norwe- gian central and northern North Sea (Figs 3, 4). The au- thors followed Mudge & Copestake (1992a, b) in aban- doning the Rogaland Group of Deegan & Scull (1977), and used Mudge & Copestake’s revised definition of the Montrose and Moray Groups for the central North Sea as well. Furthermore, the thick and hitherto undivided Horda- land Group was subdivided into two new groups, the Stronsay Group succeeded by the Westray Group, each containing a distal and a proximal formation. The two distal formations of the two groups, the Horda and Lark Formations, together constitute the bulk of the Palaeo- gene sediments in the Danish sector of the North Sea and are adopted herein (Figs 2–4). Although sandstone units occur in both the Horda and Lark Formations in the Dan- ish sector, the two proximal sandstone formations of the Fig. 3. Correlation chart showing the approximate correlation between key lithostratigraphic schemes for the central and eastern North Sea at group and formation levels. Fu r Deegan & Scull (1977) Hardt et al. (1989) Knox & Holloway (1992) This study Chalk Group Chalk Group Chalk Group Hordaland Group Lista Unnamed unit/ Våle Sele Balder Balder Balder Lista Maureen Montrose Group Moray Group Lark M o us a Sk ad e Horda Sele Rogaland Group Rogaland Group Stronsay Group Westray Group Stronsay Group Westray Group Lista Sele Horda Lark Våle Nordland Group Nordland Group Nordland Group 11 Stronsay and Westray Groups, the Mousa and Skade For- mations, are absent from the Danish sector. Following detailed analysis of new, high-resolution seismic surveys covering the succession in the eastern North Sea area, efforts were focused on establishing a sequence stratigraphic subdivision of the Palaeogene–Neogene sedi- ment package. The sedimentary succession was interpre- ted in a series of publications from a working group at the University of Aarhus (e.g. Michelsen et al. 1992, 1995, 1998; Michelsen 1993; Danielsen et al. 1997; Huuse & Clausen 2001). The result of that work was a subdivision of the Palaeogene to mid-Neogene sediment package covered by the present work into six genetic units (Fig. 4). The sequence stratigraphy of the upper Oligocene to Mi- ocene in the eastern North Sea was dealt with by Rasmus- sen (2004b). Further sequence stratigraphic contributions covering the larger North Sea Basin including the British and Norwegian sectors are given by Armentrout et al. (1993), Mudge & Bujak (1994, 1996a, b) and Neal et al. (1994). Coastal onlap Basinward 7 Michelsen et al. (1998) 6 6.3 6.2 6.1 5.4 5.3 5.2 5.1 4.4 4.3 4.2 4.1 1.2 1.1 5 4 3 2 1 Nordland Group Hordaland Group Balder Sele Lista Unnamed Unit Ekofisk CEN-5 CEN-4 CEN-3 CEN-2 CEN-1 North Sea Marl Chalk-6 Nordland Group Hordaland Group Balder Sele Sele Lista Lista Våle Ekofisk Nordland Group Lark Horda Balder Tay M o u sa S k a d e Fr ej a K o lg a F u r R in d Id un Ty r B o r Sele Lista L is ta Fo rt ie s C ro - m ar ty M ey V a d e F o rt ie s A n d re w H e im d a l H e rm o d F is k e b a n k F is k e b a n k F ri g g R o g a la n d G ro u p Maureen M a u re e n Ekofisk Ekofisk Ekofisk Nordland Group Lark Horda Balder Sele Bue Ve Vile VåleVåle Deegan & Scull (1977) NorthernNorth Sea Central North Sea Kristoffersen & Bang (1982) Hardt et al. (1989) Knox & Holloway (1992) This study Nordland Group Balder Ty Grid Ekofisk Frigg H ef - ri ng D uf a Skade Fig. 4. Correlation chart showing approximate correlation between key lithostratigraphic schemes for the central and eastern North Sea and the Norwegian part of the northern North Sea at formation and member levels. The sequence stratigraphic subdivision of Michelsen et al. (1998) is added for comparison. Sandstone-dominated units indicated in yellow. 12 Material and methods The present lithostratigraphic subdivision represents the combined results from studies of petrophysical logs, bio- stratigraphy and seismic profiles, cuttings samples and cored sections. Petrophysical logs from c. 70 wells in the Danish sector have been scrutinised (see Fig. 1 for well locations). The wells have been correlated using petrophysical logs, predominantly gamma-ray and sonic logs. Five log panels form the basis for the log correlation (Plates 1–5). Lithostratigraphic well correlation has been supported by biostratigraphic data: biostratigraphic reports from 29 wells have been re-assessed with the aim of identifying key micropalaeontological and palynological events that occur consistently within the study area (taxa used are planktonic and benthic foraminifers, diatoms, radiolaria, sporomorphs and dinoflagellate cysts). Moreover, biostrati- graphic sample suites from 11 North Sea wells have been prepared at the Geological Survey of Denmark and Green- land in order to further determine the biostratigraphic event succession. The bulk of material studied for bio- stratigraphy is based on cuttings samples, and only few Table 1. Well data for the new type and reference wells in the Danish sector of the North Sea Augusta-1 Cecilie-1 Cleo-1 Connie-1 E-8 F-1 Floki-1 Francisca-1 Frida-1 Inez-1 K-1 Mona-1 Nini-3 Sandra-1 Siri-1 Siri-2 Siri-3 Tabita-1 Bor Mb(t), Bue Mb(t),Ve Mb(t) Bor Mb(r), Tyr Mb(r) Bue Mb(r), Lista Fm(r), Ve Mb(r), Vile Mb(r) Idun Mb(t), Rind Mb(t) Bue Mb(r), Lista Fm(r), Ve Mb(r), Vile Mb(r), Våle Fm(r) Dufa Mb(r) Hefring Mb(t) Freja Mb(t) Freja Mb(r) Dufa Mb(t), Fur Fm(r) Fur Fm(r) Balder Fm(r), Horda Fm(r), Lark Fm(r) Kolga Mb(r), Tyr Mb(t) Rind Mb(r) Horda Fm(r), Lark Fm(r), Sele Fm(r), Våle Fm(r) Idun Mb(r) Balder Fm(r), Kolga Mb(t), Vile Mb(t) Sele Fm(r) 56°17´57.40´́ N 04°24´04.64´́ E 56°24´23.73´́ N 04°45´42.00´́ E 56°23´23.54´́ N 04°25´22.70´́ E 56°24´28.34´́ N 04°42´30.36´́ E 55°38´13.42´́ N 04°59´11.96´́ E 57°01´53.4´́ N 06°54´28.6´́ E 56°27´48.58´́ N 05°16´47.11´́ E 56°22´27.95´́ N 04°48´05.30´́ E 56°17´14.15´́ N 05°01´50.20´́ E 56°50´28.39´́ N 06°57´41.62´́ E 57°07´37.74´́ N 07°09´43.11´́ E 56°16´35.94´́ N 04°00´15.81´́ E 56°41´31.96´́ N 05°24´12.35´́ E 56°35´13.33´́ N 05°01´35.19´́ E 56°29´11.10´́ N 04°54´57.49´́ E 56°29´40.53´́ N 04°52´13.26´́ E 56°30´34.92´́ N 05°03´48.27´́ E 56°13´37.50´́ N 04°23´47.56´́ E 04.03.2001 2991.0 MDRT 37.8 RT 65 15.10.2000 2361.0 MDRT 37.8 RT 59.4 06.02.1984 4866.1 MDKB 40.5 KB 63.1 02.02.2001 2351.8 MDRT 37.8 RT 61.5 08.04.1994 2527.4 MDKB 36.6 KB 43.6 06.10.1968 2421.6 MDKB 37.19 KB 40.8 29.08.2000 1878 MDRT 35.8 RT 53.2 20.07.1998 1888.5 MDRT 36.4 KB 60 26.07.1997 2274 MDRT 39.0 RT 54.3 11.09.1977 1983.9 MDKB 35.1 KB 35.4 22.01.1970 2292.4 MDKB 37.2 KB 56.4 03.10.1982 4241.6 MDKB 36.6 KB 65.5 12.01.2001 1851.2 MDRT 37.3 RT 58.2 18.06.1998 2139 MDRT 36 KB 65 28.11.1995 2220 MDKB 23 KB 60 03.08.1996 2297.5 MDRT 36.6 RT 60.6 30.08.1996 2171.5 MDRT 36.6 RT 60.1 10.09.1983 4353 MDKB 40 KB 65 DONG E&P a/s DONG E&P a/s Chevron Petroleum Co. DONG E&P a/s Maersk Oil & Gas a/s Gulf Oil Company Kerr-McGee Int. aps Dansk Operatørselskab i/s Dansk Operatørselskab i/s Chevron Petroleum Co. California Oil Co. Chevron Petroleum Co. DONG E&P a/s Statoil E&P a/s Statoil E&P a/s Statoil E&P a/s Statoil E&P a/s Statoil E&P a/s Type (t) or reference (r) well Coordinates Operator Spud date TD (logger’s KB/RT elevation Water for listed units: depth in m) (m above msl) depth (m) Well Fm: Formation. Mb: Member. MDRT: Measured Depth below Rotary Table. MDKB: Measured Depth below Kelly Bushing. 13 Fig. 5. Chronostratigraphy and biostratigraphy of the Paleocene – Middle Miocene. a: Paleocene–Eocene. b: Eocene–Oligocene. c: Oligocene – Middle Miocene. Calibration of chronostratigraphic units follows Hardenbol et al. (1998), Berggren & Aubry (1996) for the Paleocene–Eocene boundary and Aubry et al. (2003) for the Sparnacian–Ypresian boundary. Key dinoflagellate datums are calibrated mainly using age estimates from Hardenbol et al. (1998) and Williams et al. (2004). Key microfossil datums are calibrated via their correlation with calibrated dinoflagellate datums as suggested by Mudge & Bujak (1996b), using age estimates from Hardenbol et al. (1998) and Williams et al. (2004). The combined event succession is correlated with the North Sea microfossil zonation of King (1989) and lithostratigraphic units treated herein. In the microfos- sil event column, the planktonic foraminifer events appear in normal font, benthic foraminifers in italics; diatoms and radiolarians are under- lined. Senoniasphaera inornata Palynodinium grallator, Dinogymnium spp. Alisocysta reticulata abundant P. pyrophorum Isabelidinium? viborgense P. pyrophorum, P. australinum acme A. gippingensis Alisocysta margarita common Cerodinium wardenense Apectodinium augustum Apectodinium augustum, acme Apectodinium spp. acme D. oebisfeldensis, influx Inaperturopollenites spp., common H. tubiferum Deflandrea oebisfeldensis Dracodinium condylos NSP6 (pars) NSP5b NSP5a NSP4 NSP3 NSP2 NSP1 a b c NSB4 (pars) NSB3b NSB3a NSB2 NSB1 a b c Horda Balder Sele Ekofisk Tor Våle Bue Ve Vile Lista Planktonic foraminifers Benthic foraminifers Diatoms and radiolaria Planktonic microfossils North Sea Biozones (King 1989) Litho- stratigraphy Selected biostratigraphic events used in the present studyGeo- chronology Ma a Chronostratigraphy (Berggren et al. 1995) C re ta ce o us (p ar s) Pa le o ce ne Eo ce ne ( pa rs ) U pp er ( pa rs ) Lo w er U pp er Lo w er ( pa rs ) Fm MbDinoflagellate cysts Ypresian (pars) Maastrictian (pars) Thanetian Sparnacian Selandian Danian 54.5 55.5 57.9 60.0 65.0 50 55 60 65 Uvigerina batjesi Turrillina brevispira Gaudryina hiltermanni common Subbotina ex gr. linaperta Fenestrella antiqua, foraminifers very rare impoverished benthic agglutinated assemblage common Globoconusa daubjergensis Globanomalina cf. compressa, S. trivialis increasing diversity of calcareous foraminifers reappearance of planktonic foraminifers increasing diversity of cal- careous benthic foraminifers Cenodiscus spp., Cenosphaera spp. Cretaceous foraminifers common F. antiqua and Coscinodiscus morsianus Pseudotextularia elegans Benthic microfossils StageSeries 14 35 40 50 45 Lark Formation Rupelian (pars) O lig o ce ne (p ar s) Eo ce ne ( pa rs ) Priabonian 41.3 Bartonian Lutetian Ypresian (pars) NSB7a NSB6b NSB6a NSB5c NSB5b NSB5a NSB4 NSB3a NSB2 (pars) NSB3b Planulina costata Pseudohastigerina spp. abundant radiolaria (Cenosphaera spp.), Cyclammina amplectens Lenticulina gutticostata, Spiroplectammina spectabilis Balder Horda Eatonicysta ursulae Diphyes ficusoides Areosphaeridium michoudii Heteraulacacysta porosa Diphyes colligerum Areosphaeridium diktyoplokum common E. ursulae Phthanoperidinium clithridium Globigerinatheka index Cibicidoides truncanus Vaginulinopsis decorata 49.0 37.0 33.7 Uvigerina batjesi Turrillina brevispira Gaudryina hiltermanni common Subbotina patagonica Dracodinium condylos Deflandrea oebisfeldensis acme D. oebisfeldensis, influx Inaperturopollenites spp., common H. tubiferum Fenestrella antiqua, foraminifers very rare Cerebrocysta bartonensis Uvigerina germanica Karrulina conversa Corrudinium incompositum Sele (pars) NSP9b NSP9a NSP8c NSP8b NSP8a NSP7 NSP6 NSP5b NSP4 (pars) NSP5a Lo w er ( pa rs ) U pp er M id dl e Lo w er ( pa rs ) Planktonic foraminifers Benthic foraminifers Diatoms and radiolaria Planktonic microfossils North Sea Biozones (King 1989) Litho- stratigraphy Selected biostratigraphic events used in the present study Chronostratigraphy (Berggren et al. 1995) Fm MbDinoflagellate cysts Benthic microfossils StageSeries Geo- chronology Ma b Fig. 5b. Chronostratigraphy and biostratigraphy of the Eocene–Oligocene. 15 Lark NSP9a (pars) NSB6b (pars) Uvigerina germanica Karrulina conversa NSP14b NSB13a NSP14a NSB12c NSP13 NSB12b NSB12a NSP12 NSB11 NSP11 NSP10 NSB10 NSB9 NSP9c NSB8c NSB8b NSB8a NSB7b NSB7a NSP9b Aulacodiscus allorgei Turrillina alsatica Bolboforma spiralis Asterigerina staeschei, Elphidium inflatum, Meonis pompilioides Uvigerina tenuipustulata Plectofrondicularia seminuda Aulacodiscus insignis quadrata (small), B. antiqua, G. girardana common Elphidium subnodosum, common Paragloborotalia nana Rotaliatina bulimoides “Turborotalia” ampliapertura common A. guerichi, Paragloborotalia opima s.s. Bolboforma metzmacheri Pararotalia canui Aulacodiscus insignis quadrata (large) Spirosigmoilinella compressa Cibicidoides mexicanus Gyroidina mamillata Wetzeliella gochtii Phthanoperidinium amoenum Chiropteridium spp. Membranophoridium aspinatum Distatodinium biffi Cordosphaeridium cantharellus Apteodinium spiridoides Caligodinium amiculum Thalassiphora pelagica Hystrichokolpoma cinctum Rhombodinium draco Corrudinium incompositum Achilleodinium biformoides Enneadocysta pectiniformis Burdigalian Aquitanian M io ce ne ( pa rs ) Lo w er Chattian U pp er Rupelian (pars) Lo w er ( pa rs )O lig o ce ne ( pa rs ) M id dl e Langhian Serravallian 28.5 23.8 20.5 16.4 14.8 11.2 Cousteaudinium aubryae Nordland Group Bulimina elongata Bolboforma clodiusi P. comatum 15 20 30 25 Cannosphaeropsis passio Tortonian (pars)U pp er (p ar s) Planktonic foraminifers Benthic foraminifers Diatoms and radiolaria Planktonic microfossils North Sea Biozones (King 1989) Litho- stratigraphy Selected biostratigraphic events used in the present study Chronostratigraphy (Berggren et al. 1995) Fm MbDinoflagellate cysts Benthic microfossils StageSeries Geo- chronology Ma c Fig 5c. Chronostratigraphy and biostratigraphy of the Oligocene – Middle Miocene. 16 core samples have been available. As the use of stratigraphic lowest occurrences (LO) of taxa in cuttings samples may be hampered due to downhole caving, the event succes- sion comprises almost exclusively stratigraphic highest occurrences (HO) of taxa (a single significant LO is in- cluded in the succession). The event succession is shown in Fig. 5a–c; its correlation with international and North Sea biozones is shown in Fig. 6a–c. Seismic sections from the 2-D and 3-D seismic surveys CGD85, DK-1, RTD81–RE94, UCG96 and UCGE97 have been used to further support the well correlation and to map the stratigraphic units in areas with only scattered well coverage. The combined results from the correlation and mapping procedures are presented as isochore maps for individual stratigraphic units. Inspection of cuttings samples from 16 key wells sup- plemented with sedimentological studies of cored inter- vals from 23 wells have formed the basis for the litholog- ical and sedimentological descriptions of the units. The well depths mentioned in the lithostratigraphy sec- tion are loggers’ depths measured either from rotary table (MDRT) or kelly bushing (MDKB). Supplementary data for new type and reference wells are provided in Table 1. The names assigned to the new lithostratigraphic units defined herein are derived from Nordic mythology and thus follow the nomenclatural tradition previously established for the Norwegian North Sea (Isaksen & Tonstad 1989). It should be noted that the micropalaeontology-based palaeoenvironmental terminology used herein was origi- nally developed for a passive margin situation (e.g. the terms ‘neritic’ and ‘bathyal’ to indicate the physiographic zones ‘shelf ’ and ‘shelf- slope’, respectively). Its application herein to the epicontinental North Sea Basin solely relates to depositional depth. Offshore and onshore lithostratigraphic nomenclature There is a high degree of lithological similarity between the Palaeogene–Neogene mudstone succession in Danish offshore boreholes and that in onshore exposures and bore- holes. However, the status of the Danish onshore units is quite varied since many units were named before a stan- dard for description of a lithostratigraphic unit was estab- lished; some fulfil these requirements, whereas others are still informal. If a previously established onshore unit and an offshore unit can be demonstrated to be identical (e.g. the Holmehus Formation and the new Ve Member pro- posed herein), the name of the onshore unit theoretically has priority over the name of the offshore unit (Salvador 1994). In other cases, names of offshore units can be ar- gued to have priority over onshore units (e.g. Sele and Balder Formations over Ølst Formation). However, in order to acknowledge the traditional distinction between offshore and onshore stratigraphic nomenclature, the two sets of nomenclature are kept separate herein. Whenever possible, comments are given in the text to explain the relationship between offshore and onshore Danish strati- graphic nomenclature. A correlation between the two sets of nomenclature is shown in Fig. 2. Chronostratigraphy and biostratigraphy Age assessment of the lithostratigraphic units in the North Sea sedimentary succession is based on correlation between key biostratigraphic events encountered in the units and the calibrated standard chronostratigraphy published by Berggren et al. (1995), with modification for the Pale- ocene–Eocene boundary following ratification of its posi- tion by the International Union of Geological Scientists (Aubry et al. 2002). The key events are from biostrati- graphic zonation schemes established for the North Sea area. Planktonic and benthic microfossils are covered by the zonation schemes of King (1983, 1989; Figs 5a–c, 6a–c). Dinoflagellates from the Paleocene and Eocene Epochs are covered by the zonation scheme of Mudge & Bujak (1996b; Fig. 6a, b); the Oligocene and Miocene Epochs are covered by the zonation schemes of Costa & Manum (1988) with modifications by Köthe (1990, 2003; Fig. 6b, c). Key events from these schemes used in this study are listed in Fig. 5a–c. For the dinoflagellate events, geochronological calibra- tion has been largely established using age estimates from Hardenbol et al. (1998), Munsterman & Brinkhuis (2004) and Williams et al. (2004). For events not mentioned in these three publications, the works of Mudge & Bujak