Lithostratigraphy

1

GEOLOGICAL SURVEY OF DENMARK AND GREENLAND BULLETIN 12 2007

Lithostratigraphy of the Palaeogene Lower Neogene succession of theDanish North Sea

Poul Schiler, Jan Andsbjerg, Ole R. Clausen, Gregers Dam,Karen Dybkjr, Lars Hamberg, Claus Heilmann-Clausen,Erik P. Johannessen, Lars E. Kristensen, Iain Prince andJan A. Rasmussen

GEOLOGICAL SURVEY OF DENMARK AND GREENLANDDANISH MINISTRY OF THE ENVIRONMENT

2

Geological Survey of Denmark and Greenland Bulletin 12

KeywordsLithostratigraphy, biostratigraphy, North Sea Basin, Palaeogene, Neogene.

CoverComplex fabric created by multiple small-scale sand intrusions (light) into dark mudstones such enigmatic fabrics are commonly associatedwith the sand-rich units of the Rogaland Group in the Siri Canyon area, offshore Denmark. The illustrated section of core is about 10 cm acrossand 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. GardeEditorial board of this series: John A. Korstgrd, Geological Institute, University of Aarhus; Minik Rosing, Geological Museum, University ofCopenhagen; Finn Surlyk, Department of Geography and Geology, University of CopenhagenScientific editors of this volume: Jon R. Ineson and Martin SnderholmEditorial secretaries: Jane Holst and Esben W. GlendalReferees: Paul van Veen (Norway) and Robert OB. Knox (UK)Illustrations: Stefan SlbergDigital photographic work: Benny M. ScharkGraphic production: Knud Gr@phic Consult, Odense, DenmarkPrinters: Schultz Grafisk, Albertslund, DenmarkManuscript received: 29 August 2005Final version approved: 8 September 2006Printed: 29 June 2007

ISSN 1604-8156ISBN 978-87-7871-196-0

Geological Survey of Denmark and Greenland BulletinThe series Geological Survey of Denmark and Greenland Bulletin replaces Geology of Denmark Survey Bulletin and Geology of Greenland SurveyBulletin.

Citation of the name of this seriesIt 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 fromGeological Survey of Denmark and Greenland (GEUS)ster Voldgade 10, DK-1350 Copenhagen K, DenmarkPhone: +45 38 14 20 00, fax: +45 38 14 20 50, e-mail: [email protected]

andGeografforlaget A/SFilosofgangen 24, 1., DK-5000 Odense C, DenmarkPhone: +45 63 44 16 83, fax: +45 63 44 16 97, e-mail: [email protected]

or at www.geus.dk/publications/bull

De Nationale Geologiske Undersgelser for Danmark og Grnland (GEUS), 2007For the full text of the GEUS copyright clause, please refer to www.geus.dk/publications/bull

3

Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Geological setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Previous work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Material and methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Offshore and onshore lithostratigraphic nomenclature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Chronostratigraphy and biostratigraphy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Paleocene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Eocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Oligocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Miocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Lithostratigraphy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Rogaland Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Vle Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Bor Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Lista Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Vile Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Tyr Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39Ve Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Idun Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Bue Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Rind Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Sele Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Kolga Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Fur Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51Balder Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Stronsay Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Horda Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Hefring Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63Westray Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Lark Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63Dufa Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69Freja Member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

4

5

Abstract

Schiler, P., Andsbjerg, J., Clausen, O.R., Dam, G., Dybkjr, 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 theDanish 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 theDanish sector of the North Sea, including some recently drilled exploration wells on the RingkbingFyn 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 theChalk Group to the base of the Nordland Group is subdivided into seven formations containingeleven new members. The existing Vle, Lista, Sele, Fur, Balder, Horda and Lark Formations of previ-ously published lithostratigraphic schemes are adequate for a subdivision of the Danish sector atformation level. Bor is a new sandstone member of the Vle Formation. The Lista Formation issubdivided 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 newsandstone member of the Horda Formation. Freja and Dufa are two new sandstone members of theLark Formation. Danish reference sections are established for the formations, and the descriptions oftheir lithology, biostratigraphy, age and palaeoenvironmental setting are updated.

__________________________________________________________________________________________________________

Authors addressesP.S.*, J.A., K.D. & L.E.K., Geological Survey of Denmark and Greenland, ster 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: [email protected]. & C.H.-C., Department of Earth Sciences, University of Aarhus, Hegh-Guldbergsgade 2, DK-8000 rhus C,Denmark.G.D. & L.H., DONG Energy, Agern All 2426, DK-2970 Hrsholm, Denmark.I.P. & E.P.J., Statoil Norway, Forusbeen 50, N-4035 Stavanger, Norway.J.A.R., Geological Museum, University of Copenhagen, ster Voldgade 57, DK-1350 Copenhagen K, Denmark.

6

Fig. 50

Fig. 56

a

Fig. 49

Fig. 56b

Fig. 61

Fig. 58

Saxo-1Wessel-1

Tordenskjold-1 Eg-1

Diamant-1

Bertel-1

Mona-1Karl-1

W. Lulu-3,-1 Cleo-1

Augusta-1

Amalie-1

Tabita-1Gulnare-1

Gwen-2 Iris-1

Baron-2

Nora-1

Elin-1W-1Ravn-1

Falk-1

U-1

E-8

Tove-1

John-Flanke-1Alma-1

Emma-1

Edna-1

Roxanne-1

Ugle-1

Frida-1L-1

Francisca-1Cecilie-1

Connie-1

Elna-1Siri-2 Siri-3

Sofie-1

Floki-1

Sandra-1

Nolde-1 Nini-1Nini-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-1Adda-2,-1Bo-1

North-Jens-1

Lulu-1Lulu-2

Sten-1

Gert-1

Kim-1

Lone-1

5700'

400' 600'

5600'

25 km

250 km

Coffee Soil Fault

NorthSea

Denmark

N

S

UK

G

NL

P

Siri C

anyo

n

Mid NorthSea High

CentralGraben

a

b

NorwegianDanish Basin

Central G

raben

100 km

North PolishStrait

EastShetlandPlatform

Fennoscandian Shield

ScottishHigh

Vik

ing

Gra

ben

Rhenish MassifBohemian

Massif

Jylland

Sjlland

Storeblt

MorayFirth

Mid NorthSea High

RingkbingFynHighFig. 1. Location maps showing the positionof wells used in the study (a) and majorstructural elements in the greater North Seaarea (b) mentioned in the text. On the wellmap (a) are indicated the locations of theseismic sections shown in Figs 49, 50, 56, 58and 61. Grey shading on this map indicatesthe margins of the Siri Canyon; grey shadinginside the canyon indicates an area ofpositive relief within the canyon. GGGGG,Germany; NNNNN, Norway; NLNLNLNLNL, Netherlands; PPPPP,Poland; SSSSS, Sweden; U KU KU KU KU K, United Kingdom.

7

Introduction

Intense drilling activity following the discovery of the SiriField in 1995 has resulted in an improved understandingof the siliciclastic Palaeogene sediment package in the Danishsector of the North Sea (Fig. 1). Many of the new wellswere drilled in the search for oil reservoirs in sandstonebodies of PaleoceneEocene age. The existing lithostrati-graphy was established on the basis of data from a gener-ation of wells that were drilled with deeper stratigraphictargets, with little or no interest in the overlying Palaeo-gene sedimentary succession. This means that this earlyscheme does not include Palaeogene sandstone units inthe Danish sector. In order to improve the understandingof the distribution, morphology and age of the Palaeo-gene sediments, in particular the economically importantsandstone bodies, a detailed study of this succession in theDanish sector has been carried out. The main aim was toupdate the lithostratigraphic framework of the successionon the basis of new data from recently drilled wells.

All of the widespread Palaeogene mudstone units inthe North Sea were established with Norwegian or Unit-ed Kingdom (UK) type wells. In the present work, theseunits have been maintained unchanged or with only slightmodifications. Danish reference wells have been establishedfor the units, however, and lithological descriptions havebeen expanded to cover the characteristics of these unitsin the Danish sector.

Many of the sandstone bodies recently discovered inthe Danish sector have a limited spatial distribution andare derived from sources different from those of most ofthe contemporaneous sandstone bodies in the Norwegianand UK sectors; furthermore, the Danish sandstone bodiesprobably neither overlap nor are in contact with the Nor-wegian/UK sandstones. These units have therefore beenestablished as new in the Danish sector, and have beenassigned Danish type and reference sections.

The lithostratigraphy presented herein (Fig. 2) has itsbase at the top of the Early Paleocene (Danian) EkofiskFormation (Chalk Group). The top of the study section isat the unconformity between the Late Eocene Mid-Mio-cene Westray Group and the Mid-Miocene to RecentNordland Group.

Oil companies operating in the North Sea have collec-ted a substantial amount of lithostratigraphic data on thePalaeogene successions and a detailed lithostratigraphy hasbeen developed for the Danish and Norwegian sectors (seee.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 geologicalsurvey organisations. It has been the aim of the presentwork formally to define these new units. This has beendone maintaining their original (albeit informal) nameswhenever feasible.

It has not been the aim of this work to provide a se-quence stratigraphic model for the Palaeogene sedimentsin the central and eastern North Sea; for this the reader isreferred 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 notattempt to review the petroleum-related aspects of thePalaeogene succession. Information about this may befound elsewhere, for example in the annual reports fromthe Danish Energy Authority.

Preliminary results from the present work, including arevised lithostratigraphic scheme, were previously pub-lished in a brief review paper (Schiler et al. 2005). Thepresent contribution formally describes the new strati-graphic units suggested in the review paper and furtherdocuments the Palaeogene Lower Neogene lithostrati-graphy in the Danish sector of the North Sea.

8

Danian

Selandian

Thanetian

Sparnacian

Ypresian

Lutetian

Ma

Mid

dle

Eoce

neLo

wer

Eoc

ene

Upp

er P

aleo

cene

Cha

lk G

roup

Rog

alan

d G

roup

Stro

nsay

Gro

up

Wes

tray

Gro

upSt

rons

ay G

roup

Low

er P

aleo

cene

Priabonian

Rupelian

Chattian

Aquitanian

Burdigalian

Langhian

Serravallian

15

20

25

30

35

45

50

55

60

65

Mid

dle

Mio

cene

Low

er M

ioce

ne

Low

er N

eoge

nePa

laeo

gene

Pala

eoge

ne

Upp

er O

ligoc

ene

Low

er O

ligoc

ene

Upp

er E

ocen

eM

iddl

e Eo

cene

LillebltClay Fm

Horda Fm

RsnsClay Fm

FurFm

F lstFm

StolleKlint Clay

ster-rende Clay

HolmehusFm

Ve Mb

Bue Mb RindMb

belFm

DanianLime-stone

Ekofisk Fm

Vle Fm

List

a Fo

rmat

ion

Vile Mb

Sele Fm

Balder Fm

Bartonian

Lutetian

40

SvindMarlFm

SvindMarlFm

Viborg Fm

Linde Clay

BrandenClay

VejleFjord Fm

HoddeFm

GramFm

Lark Fm

(undivided)

Horda Fm

Seri

es

Syst

em

Stag

e

Den

mar

kon

shor

e

DanishNorth Sea

KolgaMb

Hef-ringMb

TyrMb

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

DufaMb

Odderup Fm

BastrupSand

RibeFm

FrejaMb

IdunMb

Nor

dlan

dG

roup

ArnumFm

KertemindeMarl

LellingeGreensand

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 NorwegianDan-ish Basin (the eastern part of the northern North Sea Ba-sin of Rhys 1974) and the RingkbingFyn High (Fig. 1;the geographic terminology and names of structural ele-ments in the North Sea used herein are adapted from Rhys1974, Rnnevik et al. 1975, Deegan & Scull 1977 andFyfe et al. 2003). The western boundary of the Danishsector largely coincides with the eastern boundary of theMid North Sea High, the southern boundary largely co-incides with the southern limit of the RingkbingFynHigh, and the northern boundary is in the NorwegianDanish Basin. This basin as well as the RingkbingFynHigh are Early Permian structures. Active rifting occurredin the Central Graben from the Middle to Late Jurassicalong pre-established Palaeozoic fault trends. Major tec-tonic activity around the Palaeozoic and Jurassic struc-tures had largely ceased by Late Cretaceous time, and thesediment basin below the central North Sea was largelycharacterised by regional subsidence (Ziegler 1981).During the Late Cretaceous to Danian sea-level high, pe-lagic chalk sediments draped the structural highs and thenorthern and southern North Sea Basins became oneNorth Sea Basin delimited by the Fennoscandian Shieldto the north-east, the RheinishBohemian Massif to thesouth and the British massifs, highs and platforms to thewest (see Ziegler 1981 fig. 16 for details). Chalk sedimen-tation continued through to the end of the Danian Stagewhen it gave way to hemipelagic and siliciclastic sedimen-tation. This was probably caused by uplift of the basinmargins 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 thetime of peak uplift, in the mid-Thanetian, large sandsystems were building out towards the central North Sea.Most sediment came from the west, but the Siri Canyonsystem, a depression in the top chalk surface, was fed fromthe Fennoscandian Shield in the north-east and north (Fig1; Ahmadi et al. 2003; Hamberg et al. 2005).

Thermal subsidence centered above the Central Grabencontinued through the Eocene as sea level fell and thetemperature decreased. Shallow-marine sediments char-acterised the margins of the North Sea Basin, especiallyits western margin, whereas basinal mudstone continuedto accumulate in the basin centre and in the eastern partof 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 tofurther uplift of the basin margins and submarine fansand turbidites were deposited near the centre of the basin(Jones et al. 2003).

During the Oligocene, the North Sea Basin becamepart of a larger NW European basin. Connection withthe North Atlantic broadened and enhanced communi-cation with the oceanic water mass to the north-west,whereas the connection to the south through the NorthPolish 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 Eocenesediments 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 createdaccommodation space for thick sediment packages of basi-nal mudstones, and few sandstone units reached the basindepocentre above the Mesozoic rifts (Fyfe et al. 2003). Inthe Neogene Epoch, sediment started to be derived fromthe Fennoscandian Shield to the north, and the prograda-tion direction changed to the south-west and west in theDanish 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 PaleoceneEocene bound-ary, which is adapted from Berggren & Aubry (1996) and the age ofthe SparnacianYpresian boundary, which is from Aubry et al. (2003).Stratigraphy and ages of pre-Chatian onshore lithostratigraphic unitsare based on Heilmann-Clausen (1995) and Clemmensen & Thom-sen (2005). Post-Rupelian onshore stratigraphy and ages are fromDybkjr & Rasmussen (2000) and Rasmussen (2004a). F, Fur For-mation.

10

Previous work

The Permian to Recent lithostratigraphy of the North Seawas described in two pioneering stratigraphic works. Rhys(1974) provided an overview of the structural elements ofthe 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, Neogeneand Quaternary sediments into five major groups: theMontrose, Moray, Rogaland, Hordaland and NordlandGroups. The Montrose and Moray Groups established forthe Outer Moray Firth Forties area are proximal equiv-alents to the Rogaland Group and are not present in theDanish sector, whereas the Rogaland, Hordaland andNordland Groups have widespread distribution in theDanish sector. The succession of major mudstone forma-tions contained within the three basinwide groups has

formed the backbone of all subsequent lithostratigraphicschemes for the central and northern North Sea, includ-ing that of the present contribution.

The post-Danian Cainozoic succession of the DanishCentral Graben was divided into seven informal units byKristoffersen & Bang (1982). The Palaeogene comprisedfive units: North Sea Marl and CEN-14 (Fig. 4). Theranks of the units were not stated. Although descriptionsand interpretation of the CEN units were detailed, theyare essentially informal and have been little used.

A revised lithostratigraphy for the Palaeogene and Ne-ogene of the Norwegian North Sea sector was publishedby Hardt et al. (1989). Their lithostratigraphic schemeincludes 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 thenew 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 revisedPalaeogene stratigraphy for the Outer Moray Firth andnorthern North Sea Basins. In their papers they redefinedthe Moray and Montrose Groups of Deegan & Scull(1977) and abandoned the Rogaland Group. The authorsalso 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 fora 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 & Copestakes revised definition of theMontrose and Moray Groups for the central North Sea aswell.

Furthermore,

the

thick

and hitherto undivided Horda-

land Group was subdivided into two new groups, theStronsay Group succeeded by the Westray Group, eachcontaining a distal and a proximal formation. The twodistal formations of the two groups, the Horda and LarkFormations, together constitute the bulk of the Palaeo-gene sediments in the Danish sector of the North Sea andare adopted herein (Figs 24). Although sandstone unitsoccur 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 betweenkey lithostratigraphic schemes for the central and eastern North Seaat group and formation levels.

Fur

Deegan & Scull(1977)

Hardt et al. (1989)

Knox & Holloway(1992)

This study

Chalk Group Chalk Group Chalk Group

Hordaland Group

Lista

Unnamedunit/Vle

Sele

Balder Balder Balder

Lista

Maureen

MontroseGroup

MorayGroup

Lark

Mou

saSk

ade

Horda

Sele

RogalandGroup

RogalandGroup

StronsayGroup

WestrayGroup

StronsayGroup

WestrayGroup

Lista

Sele

Horda

Lark

Vle

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-resolutionseismic surveys covering the succession in the eastern NorthSea area, efforts were focused on establishing a sequencestratigraphic subdivision of the PalaeogeneNeogene sedi-ment package. The sedimentary succession was interpre-ted in a series of publications from a working group at theUniversity 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 subdivisionof the Palaeogene to mid-Neogene sediment packagecovered 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 contributionscovering the larger North Sea Basin including the Britishand Norwegian sectors are given by Armentrout et al.(1993), Mudge & Bujak (1994, 1996a, b) and Neal et al.(1994).

Coastal onlap

Basinward7

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

NordlandGroup

HordalandGroup

Balder

Sele

Lista

UnnamedUnit

Ekofisk

CEN-5

CEN-4

CEN-3

CEN-2

CEN-1

NorthSeaMarl

Chalk-6

NordlandGroup

HordalandGroup

Balder

Sele Sele

Lista

Lista

Vle

Ekofisk

NordlandGroup

Lark

Horda

Balder

Tay

Mo

usa

Ska

de

Frej

a

Kol

gaF

ur

Rin

dId

unTy

rBo

r

Sele

Lista

Lis

ta

Fort

ies

Cro

-m

arty

Mey

Vad

e

Fort

ies

An

dre

w

Hei

md

alH

erm

od

Fis

keb

ank

Fis

keb

ank

Fri

ggR

ogal

and

Gro

up

Maureen

Mau

reen

Ekofisk Ekofisk Ekofisk

NordlandGroup

Lark

Horda

Balder

Sele

Bue

Ve

Vile

VleVle

Deegan &Scull

(1977) NorthernNorth SeaCentral

North Sea

Kristoffersen& Bang(1982)

Hardt et al. (1989) Knox &Holloway

(1992)

This study

NordlandGroup

Balder

Ty

Grid

Ekofisk

Frigg

Hef

-ri

ngD

ufa

Skade

Fig. 4. Correlation chart showingapproximate correlation between keylithostratigraphic schemes for the centraland eastern North Sea and the Norwegianpart of the northern North Sea atformation and member levels. Thesequence stratigraphic subdivision ofMichelsen et al. (1998) is added forcomparison. Sandstone-dominated unitsindicated in yellow.

12

Material and methods

The present lithostratigraphic subdivision represents thecombined

results

from

studies

of

petrophysical

logs,

bio-

stratigraphy and

seismic

profiles,

cuttings samples and cored

sections. Petrophysical logs from c. 70 wells in the Danishsector 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

15).

Lithostratigraphic well correlation has been supportedby biostratigraphic data: biostratigraphic reports from 29

wells have been re-assessed with the aim of identifyingkey micropalaeontological and palynological events thatoccur consistently within the study area (taxa used areplanktonic and benthic foraminifers, diatoms, radiolaria,sporomorphs and dinoflagellate cysts). Moreover, biostrati-graphic sample suites from 11 North Sea wells have beenprepared at the Geological Survey of Denmark and Green-land in order to further determine the biostratigraphicevent 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), Vle 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), Vle Fm(r)Idun Mb(r)

Balder Fm(r), Kolga Mb(t), Vile Mb(t)Sele Fm(r)

561757.40 N042404.64 E 562423.73 N044542.00 E562323.54 N042522.70 E562428.34 N044230.36 E553813.42 N045911.96 E570153.4 N065428.6 E562748.58 N051647.11 E562227.95 N044805.30 E561714.15 N050150.20 E565028.39 N065741.62 E570737.74 N070943.11 E561635.94 N040015.81 E564131.96 N052412.35 E563513.33 N050135.19 E562911.10 N045457.49 E562940.53 N045213.26 E563034.92 N050348.27 E561337.50 N042347.56 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 Operatrselskab i/s

Dansk Operatrselskab 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 (loggers KB/RT elevation Waterfor 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: PaleoceneEocene. b: EoceneOligocene. c: Oligocene Middle Miocene. Calibration of chronostratigraphic units follows Hardenbol et al. (1998), Berggren & Aubry (1996) for the PaleoceneEoceneboundary and Aubry et al. (2003) for the SparnacianYpresian boundary. Key dinoflagellate datums are calibrated mainly using age estimatesfrom Hardenbol et al. (1998) and Williams et al. (2004). Key microfossil datums are calibrated via their correlation with calibrated dinoflagellatedatums as suggested by Mudge & Bujak (1996b), using age estimates from Hardenbol et al. (1998) and Williams et al. (2004). The combinedevent 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. pyrophorumIsabelidinium? viborgense

P. pyrophorum, P. australinum

acme A. gippingensis

Alisocysta margarita

common Cerodinium wardenense

Apectodinium augustumApectodinium 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

Vle

Bue

Ve

Vile

Lista

Planktonic foraminifersBenthic foraminifers

Diatoms and radiolaria

Planktonicmicrofossils

North Sea Biozones(King 1989)

Litho-stratigraphy

Selected biostratigraphic eventsused in the present studyGeo-

chronologyMa

a Chronostratigraphy(Berggren et al. 1995)

Cre

tace

ous

(par

s)Pa

leoc

ene

Eoce

ne (p

ars)

Upp

er (p

ars)

Low

erU

pper

Low

er (p

ars)

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 batjesiTurrillina brevispiraGaudryina hiltermanni

common Subbotinaex gr. linaperta

Fenestrella antiqua,foraminifers very rare

impoverished benthicagglutinated assemblage

common Globoconusadaubjergensis

Globanomalinacf. compressa, S. trivialisincreasing diversityof calcareous foraminifers

reappearance ofplanktonic foraminifers

increasing diversity of cal-careous benthic foraminifers

Cenodiscus spp.,Cenosphaera spp.

Cretaceous foraminifers

common F. antiqua andCoscinodiscus morsianus

Pseudotextularia elegans

BenthicmicrofossilsStageSeries

14

35

40

50

45

LarkFormation

Rupelian(pars)

Olig

ocen

e (p

ars)

Eoce

ne (

pars

)

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 truncanusVaginulinopsis decorata

49.0

37.0

33.7

Uvigerina batjesiTurrillina brevispiraGaudryina hiltermannicommon Subbotina patagonica Dracodinium condylos

Deflandrea oebisfeldensisacme D. oebisfeldensis, influx Inaperturopollenites spp., common H. tubiferum

Fenestrella antiqua, foraminifers very rare

Cerebrocysta bartonensis

Uvigerina germanicaKarrulina conversa

Corrudinium incompositum

Sele (pars)

NSP9b

NSP9a

NSP8c

NSP8b

NSP8a

NSP7

NSP6

NSP5b

NSP4 (pars)

NSP5a

Low

er (

pars

)U

pper

Mid

dle

Low

er (

pars

)

Planktonic foraminifersBenthic foraminifers

Diatoms and radiolaria

Planktonicmicrofossils

North Sea Biozones(King 1989)

Litho-stratigraphy

Selected biostratigraphic eventsused in the present study

Chronostratigraphy(Berggren et al. 1995)

Fm MbDinoflagellate cystsBenthic

microfossilsStageSeries

Geo-chronology

Ma

b

Fig. 5b. Chronostratigraphy and biostratigraphy of the EoceneOligocene.

15

Lark

NSP9a(pars)

NSB6b(pars)

Uvigerina germanicaKarrulina conversa

NSP14b NSB13a

NSP14a NSB12c

NSP13NSB12b

NSB12a

NSP12 NSB11

NSP11

NSP10

NSB10

NSB9

NSP9c

NSB8c

NSB8b

NSB8a

NSB7b

NSB7aNSP9b

Aulacodiscus allorgeiTurrillina alsatica

Bolboforma spiralis

Asterigerina staeschei, Elphidium inflatum, Meonis pompilioides

Uvigerina tenuipustulata

Plectofrondicularia seminuda

Aulacodiscus insignisquadrata (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 insignisquadrata (large)

Spirosigmoilinella compressa

Cibicidoides mexicanus

Gyroidina mamillata

Wetzeliella gochtii

Phthanoperidinium amoenum

Chiropteridium spp.Membranophoridiumaspinatum

Distatodinium biffi

Cordosphaeridium cantharellus

Apteodinium spiridoides

Caligodinium amiculum

Thalassiphora pelagica

Hystrichokolpoma cinctum

Rhombodinium draco

Corrudinium incompositum

Achilleodinium biformoides

Enneadocysta pectiniformis

Burdigalian

Aquitanian

Mio

cene

(par

s)

Low

er

Chattian

Upp

er

Rupelian(pars)

Low

er (p

ars)O

ligoc

ene

(par

s)

Mid

dle

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

pper

(p

ars)

Planktonic foraminifersBenthic foraminifers

Diatoms and radiolaria

Planktonicmicrofossils

North Sea Biozones(King 1989)

Litho-stratigraphy

Selected biostratigraphic eventsused in the present study

Chronostratigraphy(Berggren et al. 1995)

Fm MbDinoflagellate cystsBenthic

microfossilsStageSeries

Geo-chronology

Ma

c

Fig 5c. Chronostratigraphy and biostratigraphy of the Oligocene Middle Miocene.

16

core samples have been available. As the use of stratigraphiclowest occurrences (LO) of taxa in cuttings samples maybe hampered due to downhole caving, the event succes-sion comprises almost exclusively stratigraphic highestoccurrences (HO) of taxa (a single significant LO is in-cluded in the succession). The event succession is shownin Fig. 5ac; its correlation with international and NorthSea biozones is shown in Fig. 6ac.

Seismic sections from the 2-D and 3-D seismic surveysCGD85, DK-1, RTD81RE94, UCG96 and UCGE97have been used to further support the well correlation andto map the stratigraphic units in areas with only scatteredwell coverage. The combined results from the correlationand mapping procedures are presented as isochore mapsfor 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 datafor new type and reference wells are provided in Table 1.

The names assigned to the new lithostratigraphic unitsdefined

herein

are derived from Nordic mythology and thus

follow the nomenclatural tradition previously establishedfor

the

Norwegian

North

Sea

(Isaksen

&

Tonstad 1989).

It should be noted that the micropalaeontology-basedpalaeoenvironmental terminology used herein was origi-nally developed for a passive margin situation (e.g. theterms neritic and bathyal to indicate the physiographiczones shelf and shelf- slope, respectively). Its applicationherein to the epicontinental North Sea Basin solely relatesto depositional depth.

Offshore and onshore lithostratigraphic nomenclature

There is a high degree of lithological similarity betweenthe PalaeogeneNeogene mudstone succession in Danishoffshore boreholes and that in onshore exposures and bore-holes. However, the status of the Danish onshore units isquite 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 arestill informal. If a previously established onshore unit andan 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 theoreticallyhas priority over the name of the offshore unit (Salvador1994). In other cases, names of offshore units can be ar-gued to have priority over onshore units (e.g. Sele andBalder Formations over lst Formation). However, inorder to acknowledge the traditional distinction betweenoffshore and onshore stratigraphic nomenclature, the twosets of nomenclature are kept separate herein. Wheneverpossible, comments are given in the text to explain therelationship between offshore and onshore Danish strati-graphic nomenclature. A correlation between the two setsof nomenclature is shown in Fig. 2.

Chronostratigraphy and biostratigraphyAge assessment of the lithostratigraphic units in the NorthSea sedimentary succession is based on correlation betweenkey biostratigraphic events encountered in the units andthe calibrated standard chronostratigraphy published byBerggren et al. (1995), with modification for the Pale-oceneEocene 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 Seaarea. Planktonic and benthic microfossils are covered bythe zonation schemes of King (1983, 1989; Figs 5ac,6ac). Dinoflagellates from the Paleocene and EoceneEpochs are covered by the zonation scheme of Mudge &Bujak (1996b; Fig. 6a, b); the Oligocene and MioceneEpochs are covered by the zonation schemes of Costa &Manum (1988) with modifications by Kthe (1990, 2003;Fig. 6b, c). Key events from these schemes used in thisstudy are listed in Fig. 5ac.

For the dinoflagellate events, geochronological calibra-tion has been largely established using age estimates fromHardenbol et al. (1998), Munsterman & Brinkhuis (2004)and Williams et al. (2004). For events not mentioned inthese three publications, the works of Mudge & Bujak