geological survey of denmark and greenland bulletin 12, 1-16 · geological survey of denmark and...
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GEOLOGICAL SURVEY OF DENMARK AND GREENLAND BULLETIN 12 · 2007
Lithostratigraphy of the Palaeogene –Lower Neogene succession of theDanish 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 andJan A. Rasmussen
GEOLOGICAL SURVEY OF DENMARK AND GREENLANDDANISH MINISTRY OF THE ENVIRONMENT
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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. Korstgård, 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 SønderholmEditorial secretaries: Jane Holst and Esben W. GlendalReferees: Paul van Veen (Norway) and Robert O’B. Knox (UK)Illustrations: Stefan SølbergDigital 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)Øster 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 Undersøgelser for Danmark og Grønland (GEUS), 2007For the full text of the GEUS copyright clause, please refer to www.geus.dk/publications/bull
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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
Våle 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
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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 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 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 theChalk Group to the base of the Nordland Group is subdivided into seven formations containingeleven 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 atformation level. Bor is a new sandstone member of the Våle 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, 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: [email protected]. & 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.
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Fig. 50
Fig. 56a
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
57°00'
4°00' 6°00'
56°00'
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
Norwegian–Danish Basin
Central G
raben
100 km
North PolishStrait
EastShetlandPlatform
Fennoscandian Shield
ScottishHigh
Vik
ing
Gra
ben
Rhenish MassifBohemian
Massif
Jylland
Sjælland
Storebælt
MorayFirth
Mid NorthSea High
Ringkøbing–FynHighFig. 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 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 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 (Schiøler 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.
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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
LillebæltClay Fm
Horda Fm
RøsnæsClay Fm
FurFm
F ØlstFm
StolleKlint Clay
Øster-rende Clay
HolmehusFm
Ve Mb
Bue Mb RindMb
ÆbeløFm
DanianLime-stone
Ekofisk Fm
Våle Fm
List
a Fo
rmat
ion
Vile Mb
Sele Fm
Balder Fm
Bartonian
Lutetian
40
SøvindMarlFm
SøvindMarlFm
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 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 Rhys1974, Rønnevik 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 Ringkøbing–FynHigh, and the northern boundary is in the Norwegian–Danish Basin. This basin as well as the Ringkøbing–FynHigh 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 Rheinish–Bohemian 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 Paleocene–Eocene bound-ary, which is adapted from Berggren & Aubry (1996) and the age ofthe Sparnacian–Ypresian 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 fromDybkjær & 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-1–4 (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 & Copestake’s 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 2–4). 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/Våle
Sele
Balder Balder Balder
Lista
Maureen
MontroseGroup
MorayGroup
Lark
Mou
saSk
ade
Horda
Sele
RogalandGroup
RogalandGroup
StronsayGroup
WestrayGroup
StronsayGroup
WestrayGroup
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-resolutionseismic surveys covering the succession in the eastern NorthSea area, efforts were focused on establishing a sequencestratigraphic subdivision of the Palaeogene–Neogene 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
Våle
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
VåleVåle
Deegan &Scull
(1977) NorthernNorth Sea
CentralNorth 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
1–5).
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), 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´́ N04°24´04.64´́ E 56°24´23.73´́ N04°45´42.00´́ E56°23´23.54´́ N04°25´22.70´́ E56°24´28.34´́ N04°42´30.36´́ E55°38´13.42´́ N04°59´11.96´́ E57°01´53.4´́ N06°54´28.6´́ E56°27´48.58´́ N05°16´47.11´́ E56°22´27.95´́ N04°48´05.30´́ E56°17´14.15´́ N05°01´50.20´́ E56°50´28.39´́ N06°57´41.62´́ E57°07´37.74´́ N07°09´43.11´́ E56°16´35.94´́ N04°00´15.81´́ E56°41´31.96´́ N05°24´12.35´́ E56°35´13.33´́ N05°01´35.19´́ E56°29´11.10´́ N04°54´57.49´́ E56°29´40.53´́ N04°52´13.26´́ E56°30´34.92´́ N05°03´48.27´́ E56°13´37.50´́ N04°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 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: Paleocene–Eocene. b: Eocene–Oligocene. c: Oligocene –Middle Miocene. Calibration of chronostratigraphic units follows Hardenbol et al. (1998), Berggren & Aubry (1996) for the Paleocene–Eoceneboundary and Aubry et al. (2003) for the Sparnacian–Ypresian 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
Våle
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 Eocene–Oligocene.
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. 5a–c; its correlation with international and NorthSea biozones is shown in Fig. 6a–c.
Seismic sections from the 2-D and 3-D seismic surveysCGD85, DK-1, RTD81–RE94, 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 Palaeogene–Neogene 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 Ølst 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-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 Seaarea. Planktonic and benthic microfossils are covered bythe zonation schemes of King (1983, 1989; Figs 5a–c,6a–c). 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 Köthe (1990, 2003;Fig. 6b, c). Key events from these schemes used in thisstudy are listed in Fig. 5a–c.
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