geological indications for palaeogene uplift in the eastern north sea basin

Ž .Global and Planetary Change 24 2000 175–187www.elsevier.comrlocatergloplacha

Geological indications for Palaeogene uplift in the eastern NorthSea Basin

Ole Rønø Clausen), Ole Bjørslev Nielsen, Mads Huuse, Olaf Michelsen˚Department of Earth Sciences, UniÕersity of Aarhus, DK-8000 Arhus C, Denmark

Received 8 November 1999

Abstract

The timing and effect of the Cenozoic uplift of Scandinavia has been investigated using a multi-disciplinary approachinvolving sedimentological, seismic and biostratigraphic data from the Danish and the adjacent Norwegian parts of the NorthSea Basin. It is concluded that significant uplift took place periodically throughout the Palaeogene possibly marking anearlier onset of the so-called ‘‘Neogene uplift’’ of Scandinavia. This conclusion is based on a number of sedimentologicalobservations, including smectite content, grain-size variations, kaolinite thermal stabilities and T values supported bymax

seismic reflection geometries and biostratigraphic data. These data indicate several phases of re-working of Palaeogene andolder sediments situated further to the east and northeast during the middle to late Eocene and during the middle to lateOligocene. The tectonic patterns were similar during the late Paleocene and the Oligocene with some inversion taking place,whereas no inversion has been observed during the Eocene. Main provenance areas were to the north and northeast duringthe Paleocene and Oligocene, whereas the Eocene sediments originate mainly from the British Isles to the west. It isproposed that Palaeogene uplift of Scandinavia was associated with regional tectonic movements along crustal zones ofweakness, which were reactivated as they accommodated strain induced by the Alpine Orogeny and the opening of the NorthAtlantic. q 2000 Elsevier Science B.V. All rights reserved.

Keywords: Palaeogene uplift; Eastern North Sea Basin

1. Introduction

During the post-Danian Cenozoic, the North Seaarea constituted an epicontinental basin which wasfilled with siliciclastic sediments supplied from theeast and the west and, for the Norwegian–Danish

Ž .Basin, from the north Michelsen et al., 1998 . TheCenozoic North Sea Basin is centred above the

Ž .Mesozoic Central Trough Fig. 1 . The subdivision

) Corresponding author. Tel.: q45-89-42-25-18; fax: q45-89-42-25-25.

Ž .E-mail address: [email protected] O.R. Clausen .

of the Cenozoic succession in the Danish North Seais based mainly on the sequence stratigraphic analy-

Ž .sis presented by Michelsen et al. 1995, 1998 . Bymeans of biostratigraphy, the sequences are relatedto the lithostratigraphic units defined onshore Den-

Ž . Ž .mark Fig. 2 Michelsen, 1994 .The uplift of the eastern margin of the North Sea

ŽBasin has generally been dated as Neogene Jensenand Michelsen, 1992; Jensen and Schmidt, 1992;

.Japsen, 1993, 1998 . The objective of this paper is todemonstrate that the Cenozoic uplift of the easternmargin of the North Sea Basin was initiated duringthe Palaeogene. The work is based on well data

0921-8181r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved.Ž .PII: S0921-8181 00 00007-2

( )O.R. Clausen et al.rGlobal and Planetary Change 24 2000 175–187176

Ž . ŽFig. 1. The map shows the present topography of the Top Chalk surface ms TWT in the eastern and central North Sea from Day et al.,.1981; Clausen and Huuse, 1999 . The topography of the Top Chalk surface reflects the shape of the Cenozoic siliciclastic North Sea basin.

Ž . ŽSuperposed on the map are the outlines of the major Mesozoic grabens: the Horn Graben Triassic and the Central Trough Jurassic–lower. Ž .Cretaceous , and the Sorgenfrei–Tornquist zone from Vejbæk, 1997 . The locations and wells referred to in the text are also indicated. The

position of the geosection in Fig. 3 is indicated.

Ž .mainly cuttings and well logs , outcrops, and seis-mic sections from the Danish and Norwegian NorthSea. The analyses comprise composition and textureof the sediments, sequence stratigraphic develop-ment, biostratigraphy and tectonic patterns.

1.1. Sediment characteristics

The Paleocene and Eocene sediments are gener-ally very fine-grained clays, with small amounts of

Ž .silt dominated by quartz and muscovite . The de-posits are very homogeneous throughout their distri-bution area in the Danish and the southern part of theNorwegian sector, both with respect to thickness,

Ž .composition and distribution Nielsen et al., 1986 .ŽThe youngest Eocene sediments the Søvind Marl

.Formation show an increasing content of carbonatestowards the east, caused by in-situ production of

carbonate rather than reworking of older depositsŽ .Erik Thomsen, pers. commun. . Generally, there is ahiatus between the upper Eocene Søvind Marl For-mation and the Lower Oligocene Viborg Formation.On the Ringkøbing-Fyn High and in southernJutland, the Viborg Formation and the overlyingBranden Clay is absent. The base of the Oligocenesuccession shows a clear change in lithology fromfine-grained clays below the boundary to a clayeysilt with mica above. The Oligocene deposits arefurthermore characterised by a higher content ofillite and kaolinite than in the underlying smectite-dominated Eocene deposits. Seismic mapping andinterpreted facies distribution indicate a pronouncedprogradation from the northeast during the Oligocenewhich is in marked contrast to the generally concor-dant reflection pattern observed in the underlyingEocene succession in the Danish area. The changes

( )O.R. Clausen et al.rGlobal and Planetary Change 24 2000 175–187 177

Fig. 2. The correlation of the Palaeogene lithostratigraphy fromŽ .the UK sector and onshore Denmark from Michelsen, 1994 .

from the Eocene to the Oligocene were probablycaused by uplift of the source areas situated to the

Ž .E–NE e.g. Spjeldnæs, 1975 . Furthermore, the dis-tribution area of the Viborg Formation is very differ-ent from that of the Eocene formations, as the Vi-borg Formation is absent on the onshore part of theRingkøbing-Fyn High in southern Jutland and in thenorthwesternmost part of Jutland. The micaceousclays of the Viborg Formation is the oldest lithologyshowing these characteristics.

2. General geometry of the Cenozoic succession

The architecture of the Cenozoic succession in theeastern and central North Sea is illustrated by means

Žof a geosection showing the present geometry Fig..3a and a reconstructed section flattened at the

Ž .‘‘mid-Miocene unconformity’’ Fig. 3b . The‘‘mid-Miocene unconformity’’ is assumed to repre-sent a surface that originally was close to beinghorizontal. The extrapolation of the ‘‘mid-Mioceneunconformity’’ to the northeast, as indicated with adashed line in Fig. 3a, provides the basis for the

Ž .Fig. 3. A geosection illustrating the geometry of the Cenozoic succession in the eastern North Sea modified from Nielsen et al., 1986 . ForŽ . Ž .location, see Fig. 1. The ‘‘mid-Miocene unconformity’’ is extrapolated to the east a , and b shows a reconstructed section flattened at the

‘‘mid-Miocene unconformity’’. See text for further explanation.


reconstructed section in Fig. 3b. The present distribu-tion of the Upper Paleocene to mid-Miocene succes-sion shows a minor thickening in the centre of thebasin. The reconstructed section emphasises thesheet-like character of the Upper Paleocene succes-sion, and that the depositional centre was located tothe west during the Eocene and to the east during theOligocene–Early Miocene. The internal geometry ofthe major sequences is indicated schematically and itillustrates that the Eocene succession in the DanishCentral Trough was supplied from the British Islandsto the west, whereas the Oligocene–mid-Miocenesediments were supplied from the north–northeastŽ .Michelsen et al., 1995 .

3. Eocene–Oligocene geological evolution

3.1. Incisions into the top of the Eocene deposits

On the northern flank of the Ringkøbing-FynHigh in the Danish North Sea, a number of incisionsat the base of the Oligocene succession are inter-

Ž .preted on high-resolution seismic profiles Fig. 4 .The incisions cut into a local depositional centre of

Žthe uppermost Eocene Søvind Marl Formation Fig..5 . Maximum depth of incision is 30 m with a

maximum width of 500 m and a total length of lessthan 20 km. Timing of incision is only looselyconstrained as the nearest well control is about 50

Ž .km away R-1 and because of the condensed charac-ter of the Oligocene deposits on the Ringkøbing-FynHigh. It is thus not clear whether incision took placeat the Eocene–Oligocene transition or some timelater in the Oligocene. North of the area shown inFig. 5, 2–300 m high clinoforms of the Oligocenesuccession indicate that these sediments were fedinto relatively deep water. This is confirmed by therelatively large palaeo-water depths inferred for the

Ž .Søvind Marl deposition Heilmann-Clausen, 1995 .The incisions are generally parallel to the con-

Žtours of the Søvind Marl Formation isochors NE–.SW, Fig. 5 , suggesting that incision may have been

caused by submarine erosion, e.g. geostrophic cur-rents. The incisions are also partly parallel with the

Ž .Holmsland Fault Figs. 1 and 5 .The top of the Søvind Marl Formation is di-

achronous in eastern Jutland. The oldest parts arefound at the ends of a profile running north–southfrom Harte in the north to Bøgeskov in the southwith the youngest parts in the centre of the profile at

Ž . Ž .Kysing Fig. 6 Larsen, 1993 . The age variationsmay indicate that regional erosion affected the top ofthe Søvind Marl Formation in eastern Jutland. To thenorth, the Søvind Marl Formation is overlain by theLower Oligocene Viborg Clay. To the south, it isoverlain by the Upper Oligocene–Lower Miocene

Ž .Vejle Fjord Formation Ulleberg, 1987 . The pro-posed regional erosion in the eastern part of Jutlandis in contrast to the local incision west of Jutland and

Ž .Fig. 4. High-resolution seismic section DA95-14 showing incisions into the top of the uppermost Eocene Søvind Marl Formation. Insertedmap shows the location of the section.


Ž .Fig. 5. Detailed map based on interpretation of high-resolution seismic data DA94, DA95 and DA96 showing the extent and orientation ofincisions into the top of the uppermost Eocene Søvind Marl Formation.

Ž . Ž .Fig. 6. Detailed map a from central Jutland showing lateral variations in the age of the top of the Søvind Marl Formation. The scheme bŽ . Ž .shows the correlation between the NP zonation Martini, 1971 and the Eocene succession. The ages are based on Larsen 1993 ,

Ž . Ž .Heilmann-Clausen 1995 and Thomsen 1995 .


may indicate that eastern Jutland was uplifted rela-tive to the area west of Jutland.

3.2. Smectite content indicating sediment reworkingin the middle Eocene

The smectites in the Cenozoic North Sea sedi-ments are generally believed to originate from trans-formation of volcanic ash from eruptions during thelate Paleocene and early Eocene, related to the open-ing of the north Atlantic Ocean between Norway andGreenland. Presence of zeolites is normally associ-ated with the presence of ash layers and high smec-tite contents of the sediments. The proportion ofsmectite generally decreases upwards from the Lower

Ž .Eocene sediments Nielsen, 1994 . Onshore, thetransition between the L4 and L5 beds of the middleEocene Lillebælt Clay is characterised by an abruptupward increase in the smectite content, occasionallyassociated with sporadic presence of zeolithes in the

Ž .lowermost part of Bed L5 Fig. 7 . This is consid-

ered as indicating supply of reworked Paleocenerlower Eocene smectite-rich sediments from sourceareas located east of Denmark. After this event, thepattern of upward decreasing smectite content isre-established. A similar abrupt increase in the smec-tite content is observed in the Danish Central Trough.

3.3. Grain-size analyses indicating sediment rework-ing in the middle Eocene

Analyses of grain-size distribution of Upper Pale-ocene sediments in the Rødbyhavn area on LollandŽ .Fig. 1 have demonstrated an extraordinary sensitiv-ity to drying temperature prior to analyses. Dryingthe samples at 408C, 508C and 1058C causes areduction in the number of clay-sized particles fromapproximately 75% to 25% when compared tograin-size distribution of undried material. Analysesof post-lower Eocene sediments from Rødbyhavnand all other Cenozoic and Mesozoic sediments fromthe Danish area do not show any sensitivity to drying

Fig. 7. The relative proportions of the different clay minerals from the Viborg-1 well. Note the changes in relative amounts of smectiteswithin the Lillebælt Clay. See text for further discussion.


temperature from 408C to 1058C, except sedimentsfrom the L5 bed at localities in the eastern part ofJutland. This indicates that the source area for the L5bed might have been exposed Upper Paleocenesmectite-rich sediments, having an extraordinarilyhigh tendency for clay-sized particles to form silt-sized aggregates at very low drying temperatures.Thus, it appears that Upper Paleocene sedimentswere exposed to erosion along the eastern basinmargins during the Eocene.

3.4. Reworking of nanno- and micro-fossils

Substantial amounts of reworked Cretaceousnanno-fossils are known from the Upper Paleocene

Ž .Kerteminde Marl von Salis Perch-Nielsen, 1994 ,

and are probably related to the inversion of theSorgenfrei–Tornquist Zone in the Kattegat in Late

ŽCretaceousrEarly Paleocene times Liboriussen et.al., 1987 . In the Harre and Linde-1 boreholes in

Ž .north Jutland Fig. 1 , the Lower Oligocene ViborgFormation contains a significant amount of reworkedCretaceous nanno-fossils and, especially in the lower

Žpart, also Eocene species von Salis Perch-Nielsen,.1994; Laursen, 1995 . This is in contrast to the

underlying Eocene sediments that do not show sig-nificant amounts of reworked micro-fossils. TheBranden Clay, which overlies the Viborg Formation,contains no reworked Cretaceous nanno-fossils, butsome PaleocenerEocene nanno-fossils. The presenceof reworked Paleocene and Eocene nanno-fossils inOligocene sediments is interpreted be the result of

Ž . Ž .Fig. 8. Base Oligocene time–structure map compiled from Jordt and Michelsen 1992 and Clausen 1995 . Superimposed are the majorMesozoic faults generating the Mesozoic Central Graben and the Horn Graben. The correlation between the major faults cutting the Toppre-Zechstein surface and the topography of the base Oligocene in the northern Danish Central Trough indicates tectonically controlleddifferential subsidence in post-Eocene time.


denudation of PaleocenerEocene sediments exposedat the basin margin to the east.

3.5. Kaolinite thermal stability and T Õalues indi-m a x

cating sediment reworking during the middle andlate Oligocene

Normally, kaolinite becomes more stable withrespect to temperature under progressive diagenesisŽ .Dunoyer de Segonzac, 1970 . Sediments derivedfrom areas with subsidence followed by uplift andsubsequent erosion will exhibit reverse thermal sta-bility of kaolinites. In Jutland, part of the kaolinites

Žfrom the Vejle Fjord Formation Upper Oligocener.Lower Miocene is more heat resistant than kaolin-

ites of the underlying sediments. This is interpretedto be due to a supply of reworked older sedimentsfrom an uplifted area to the east. It seems likely thatthe source area for the kaolinites with higher thermalstability should be found where the uplift and ero-sion has been most pronounced, i.e. in areas influ-enced by both the Late CretaceousrEarly Paleoceneinversion and by the regional uplift of Scandinavia.T values obtained through analysis of the matu-max

rity of organic material normally increase with in-creasing depth reflecting the diagenetic maturationdue to increased formation temperature. T valuesmax

from the Lulu-1 well in the Central Trough demon-strate a sudden upwards increase of T in themax

Oligocene sediments, close to the transition betweenŽ .Lower and Upper Oligocene Danielsen, 1989 . The

sudden increase is interpreted to reflect the rework-ing of uplifted, probably Mesozoic, sediments to theeast.

3.6. Tectonic eÕents

The time–structure map of the base of theŽ .Oligocene deposits Fig. 8 shows a detailed correla-

tion between the deep basement-rooted faults and thechanges in gradient of the base Oligocene in the

Ž .Central Trough area Fig. 8 . This indicates post-Eocene reactivation of the faults in the CentralTrough area. Analyses of the Oligocene sequencegeometries also indicate that reactivation of base-ment faults in the Central Trough area took place

Žduring the Oligocene Clausen and Korstgard, 1993;˚.Danielsen et al., 1997 . The Oligocene deformation

pattern observed in the Central Trough shows thatinversion along the Arne–Elin trend took place si-

Fig. 9. Detailed view of the northern part of the Danish CentralTrough showing the possible shear causing both inversion anddifferential subsidence during the late Paleocene as well as theOligocene. CT, RFH, and NDB indicates the Central Trough,Ringkøbing-Fyn High and Norwegian–Danish Basin respectively.See text for further discussion.

multaneously with minor differential subsidence inthe Tail-End Graben, and major differential subsi-

Ždence in the Søgne Basin area Clausen and.Korstgard, 1993 . The spatially varying deformation˚

pattern is interpreted to be caused by minor right-lateral shear movements with an orientation as indi-cated in Fig. 9. Right-lateral shear reactivated thedeeper Mesozoic basement faults with various strikes,e.g. the faults beneath the Arne–Elin trend and theCoffee–Soil Fault.

4. Discussions

4.1. Eustacy

The influence of eustacy on the Cenozoic sedi-mentological record in the North Sea Basin has been

Žthe subject of many publications e.g. Galloway etal., 1993; Jordt et al., 1995; Michelsen et al., 1995,

.1998; Sørensen et al., 1997 . The overall trend ofeustacy during the Cenozoic is one of falling sealevel since the mid-Eocene corresponding to the time

Žof onset of Southern Hemisphere glaciations Abreu.and Anderson, 1998 . Major changes in the rate of

long-term sea-level fall occurred at the Eocene–ŽOligocene transition and at mid-Miocene time e.g.


.Abreu and Anderson, 1998 . It is thus anticipatedthat Cenozoic differential uplift of the basin marginsacted on a background of glacio-eustatic variations atleast since the middle Eocene. The effect of long-termeustatic lowering would be enhanced erosion of basinmargins, probably responsible for the globally occur-ring increase in sediment input at the Eocene–Oligocene transition. Higher frequency sea-levellowerings may be responsible for supplying pulses ofproximal sediments to the central part of the NorthSea Basin. However, the available data preclude thateustacy is the sole mechanism responsible for varia-tions in sediment input into the North Sea Basin, asdifferent source areas were made available at differ-ent times throughout the Palaeogene. This effect can

Žonly have been produced by active tectonics i.e..uplift of basin margins in the North Sea area.

4.2. Eocene uplift along the eastern margin of theNorth Sea Basin

The upward increase in smectite content withinthe Lillebælt Clay is interpreted to reflect reworkingof Upper Paleocene sediments east of the Danishonshore area. This is in agreement with indicationsof westerly sediment transport directions in parts ofthe Eocene succession in the Central Trough areaŽ .Clausen, 1995 . The uppermost Eocene sedimentsshow an increasing content of carbonate towards theeast grading into the marls of the Søvind MarlFormation, which is present in the eastern North Seaand onshore Denmark. This indicates a progressivelyshallower sea towards the east during the latest

Ž .Eocene Michelsen et al., 1995 . We have notseen positive indications in the seismic sections of

Ž . Ž . Ž .Fig. 10. Thickness map of the Eocene succession a . The thicknesses are from Dinesen et al. 1977 and Nielsen 1994 , and the QuaternaryŽ .erosional truncations of the top Eocene and base Eocene are from Hakansson and Petersen 1992 . The faults at the Top Chalk surface˚

Ž .indicated in gray are from Ter-Borch 1990 . The contours are based on a rather small number of wells, which are indicated with dots. TheŽ . Ž .faults at the Top pre-Zechstein b from Vejbæk 1997 show the basement structures, and especially the blocks of the Ringkøbing-Fyn

High. The Grindsted, Holmsland and Glamsbjerg Blocks are shown. The Glamsbjerg and Grindsted Blocks are separated by the BrandeTrough, whereas the Grindsted and Holmsland Blocks are separated by the Holmsland Fault. See text for further discussion.


reactivation of basement-rooted faults during theEocene. However, the thickness distribution of theentire Eocene succession onshore DenmarkŽ .includingthe Søvind Marl Formation , derived fromDinesen

Ž .et al. 1977 , indicate that the Eocene successionthickens along fault-trends north and south of theRingkøbing-Fyn High, and thins above the Grindsted

Ž .Block of the Ringkøbing-Fyn High Fig. 10a . Thestructural subdivision of the Ringkøbing-Fyn High isindicated in Fig. 10b, which shows the faults at Toppre-Zechstein. The fault-trends observed at the TopChalk surface north and south of the Ringkøbing-FynHigh detach along the top of the Zechstein saltŽBritze et al., 1992; Vejbæk, 1997; Clausen and

.Huuse, 1999 and are thus not directly related tobasement faulting. The thickness distribution of theSøvind Marl Formation and the Lillebælt Clay For-

Ž .mation Fig. 11a,b indicate that the formations

thicken above the fault trends running north andsouth of the Ringkøbing-Fyn High and thins abovethe Grindsted Block, with a pronounced thickeningin a zone striking N–S corresponding to the Brande

Ž .Trough Figs. 10b and 11a,b . Offshore in the east-ern North Sea, mapping of the Søvind Marl Forma-tion on high-resolution seismic data indicates that theSøvind Marl Formation is thinnest at the westernpart of the Grindsted Block and thickens above the

Ž .Holmsland Block Fig. 11a . On the HolmslandŽBlock, erosion is seen as minor incisions Figs. 4 and

.5 . The timing of regional erosion at the top ofSøvind Marl Formation in eastern Jutland is con-strained by the age of the overlying Viborg Forma-tion, which contains a large number of reworkedmicro-fossils from the Søvind Marl Formation. Theage variation along the top of the Søvind MarlFormation and the reworked micro-fossils indicatethat differential subsidence created a relative low

Ž . Ž .Fig. 11. Maps showing the thickness distribution of the Søvind Marl Formation a and the Lillebælt Clay b . The thicknesses are fromŽ . Ž .Dinesen et al. 1977 and Nielsen 1994 , and the Quaternary erosional truncations of the top Eocene and base Eocene are from Hakansson˚Ž . Ž .and Petersen 1992 . The faults at the Top Chalk surface indicated in gray are from Ter-Borch 1990 . The contours are based on a rather

small number of wells, which are indicated with dots. See text for further discussion.


along the northern flank of the Ringkøbing-Fyn HighŽ .e.g. at Kysing prior to deposition of the Viborg

Ž .Formation Fig. 6 . The significant thickness varia-tions of the Søvind Marl Formation may reflectsynsedimentary differential subsidence. However, theobservations only allow us to conclude that thethickness distribution is due to differential subsi-dence and that erosion at the top of the Søvind MarlFormation took place between deposition of theSøvind Marl Formation and the Viborg Formation,i.e. at the Eocene–Oligocene transition.

The palaeo-water depth during deposition of theŽ .Røsnæs Clay Formation Lower Eocene onshore

ŽDenmark is interpreted as 600–1000 m Heilmann-.Clausen, 1995 and the total thickness of the Eocene

Ž .succession does not exceed 150 m Fig. 10a , exceptalong the fault trend south of the Ringkøbing-FynHigh. The widespread erosion at the top of theSøvind Marl Formation indicates a significant shal-lowing of the eastern part of the basin. This shallow-ing cannot be fully accounted for by the global fallin sea level taking place during the Middle and LateEocene. It is thus suggested that the observed shal-lowing of the eastern part of the basin and input ofsediment from the east was caused by tectonicallyinduced uplift of the eastern basin margin during theLate Eocene.

4.3. Oligocene uplift

The facies distribution and sequence geometry ofthe Oligocene deposits indicate that a new sedimentsource area was made available to the northeastŽ .Michelsen et al., 1995; Danielsen et al., 1997 . Thevariations in thermal stability of kaolinite within theOligocene succession, the presence of reworked mi-cro-fossils in parts of the Oligocene succession andthe change in T values all indicate that the rocksmax

which were eroded and sourced the progradingOligocene sediments changed in composition duringthe Oligocene. Seismic mapping indicates that thereactivation of basement structures took place duringthe Oligocene and introduced differential subsidenceand inversion in the Central Trough area and that theNorwegian–Danish Basin subsided relative to theRingkøbing-Fyn High. The tectonic activity and thesynchroneity between the observed tectonic eventsand the Alpine orogeny and the opening of the North

Atlantic, as outlined for the Central Trough area byŽ .Clausen and Korstgard 1993 , suggest that tectonic˚

uplift of the eastern margin of the North Sea Basintook place periodically during the Oligocene.

4.4. The Eocene–Oligocene eÕolution compared tothe Late Paleocene eÕolution

Late Paleocene inversion tectonism has been doc-umented in large parts of the North Sea Basin and inthe Danish area especially along the Sorgenfrei–Tornquist Zone and along Mesozoic fault-trends in

Žthe Central Trough Liboriussen et al., 1987; Vejbækand Andersen, 1987; Ziegler, 1990; Clausen and

.Korstgard, 1993 . The deformation pattern in the˚Central Trough during the Oligocene, as describedabove, is identical with the inversion pattern ob-

Žserved for the late Paleocene Clausen and Korstgard,˚1993; Clausen and Huuse, 1999; Danielsen et al.,

.1995 . As shown in Fig. 3, the Upper Paleocenesuccession differs from the Oligocene succession inthe Norwegian–Danish Basin and the Central Trougharea. The Oligocene shows pronounced progradation

Ž .from the N and NE Danielsen et al., 1997 com-pared to the relatively thin and the generally con-densed character of the Upper Paleocene sediments.However, the Upper Paleocene succession showssouthwestward progradation in the Norwegian sectorŽ .Michelsen et al., in press . The erosional patternobserved at the Top Chalk surface indicates that theeastern part of the North Sea Basin was topographi-

Žcally higher than the central parts Clausen and.Huuse, 1999 . This is also indicated by the presence

of silt and sandprone Upper Paleocene intervals,which are interpreted to originate from the northeast,

Ž .in the Central Trough area Danielsen et al., 1995 .The similar deformation patterns observed during

the Paleocene and the Oligocene indicate a similarmechanism for generating the deformation. The dif-ference in sequence geometry and sediment composi-tion between the Upper Paleocene and the Oligocenesediments is thus interpreted to be a consequence ofdifferences in composition of the source area rockscombined with the changes of relative sea level andlocation of shorelines.

The western source area of the main part of theEocene sediments and the absence of inversion tec-tonics in the eastern North Sea Basin reveal that the


Eocene basin evolution differs significantly from thedevelopment during the late Paleocene andOligocene. The eastward sediment transport mayreflect that the uplift of the western margin of theNorth Sea Basin dominated over uplift along theeastern margin of the North Sea Basin during theEocene. However, the periodical input of sedimentsin the eastern part of the North Sea Basin from theeast is well documented and the dominantly eastwardsediment transport thus only indicates that rates ofdenudation during the Eocene were higher along thewestern margin than along the eastern margin of theNorth Sea Basin. The periodical input of sedimentsfrom the east and the evolution of the palaeo-waterdepth through the Eocene indicate an overall shal-lowing towards the east and exposure of land massesdue to uplift along the eastern margin of the NorthSea Basin.

5. Conclusions

The multi-disciplinary investigation of the Palaeo-gene succession in the eastern North Sea Basin,involving analyses of lithological, palaeontologicaland organic maturity data combined with seismicreflection geometries, lead us to conclude that tec-tonic uplift of the eastern margin of the North SeaBasin took place during the Palaeogene.

Direct indications regarding uplift of the easternmargin of the North Sea Basin during the late Pale-ocene are sparse. However, inversion tectonics in theCentral Trough, the erosional pattern at Top Chalk,and the occurrence of Upper Paleocene sandy inter-vals in the Norwegian–Danish Basin and the CentralTrough all indicate that uplift of the eastern marginof the North Sea Basin took place during the LatePaleocene.

The thickness distribution of the Eocene sedi-ments suggests that basement tectonics were active,and intervals with reworked older sediments indicatean easterly located source area. It is, however, notpossible to conclude whether land masses were ex-posed east of the North Sea Basin throughout theEocene or only periodically.

The massive southwestward progradation duringthe Oligocene indicates the presence of a new sourcearea exposed for erosion towards the northeast. Thisis also reflected in the mineralogical variations and

the kaolinite stability observed in parts of the lateOligocene succession. The tectonism observed onseismic data, the sediment transport directions, andthe sediment characteristics indicate the exposure ofland east of the North Sea Basin during theOligocene. The observed tectonic movements lead usto suggest a tectonic origin for the relative uplift ofthe eastern margin of the North Sea Basin during theOligocene.

The occurrence of tectonism and the indicatedcontrol of tectonism onto location of depositionalcentres and erosion lead us to suggest that thePalaeogene uplift of the eastern margin of the NorthSea Basin was highly influenced by regional tectonicmovements along weak crustal zones. These zoneswere probably reactivated during accommodation ofstrain from an interaction of the Alpine Orogeny andthe opening of the North Atlantic.

Acknowledgements

The high-resolution seismic sections were ac-quired by the Department of Earth Sciences, Univer-sity of Aarhus and funded by the Danish Natural

ŽScience Research Council grant no. 9401161,.9502760 and 9701761 , who also funded the second

part of Mads Huuse’s PhD-scholarship. Erik S. Ras-mussen, Lars N. Jensen and James A. Chalmers arethanked for a constructive review.

References

Abreu, V.S., Anderson, J.B., 1998. Glacial eustacy during theCenozoic: sequence stratigraphic implications. Am. Assoc.Pet. Geol. Bull. 82, 1385–1401.

Britze, P., Japsen, P., Langtofte, C., 1992. Major structural ele-ments of the Danish Basin. In: European Association ofPetroleum Geoscientists and Engineers, 4th Conference andTechnical Exhibition, p. 52.

Clausen, O.R., 1995. Tertiary seismic stratigraphy in the NorthernDanish Central Trough. Aarhus Geosci. 2, 95.

Clausen, O.R., Huuse, M., 1999. Topography of the top chalksurface on- and offshore Denmark. Mar. Pet. Geol. 16, 677–691.

Clausen, O.R, Korstgard, J.A., 1993. Tertiary tectonic evolution˚along the Arne–Elin Trend in the Danish Central Trough.Terra Nova 5, 233–243.

Danielsen, M., 1989. En sedimentologisk analyse af Tertiæresedimenter i de danske Nordsøboringer Lulu-1 og Inez-1.

˚Unpublished MSc thesis, Aarhus Universitet, Arhus, 226 pp.Danielsen, M., Clausen, O.R., Michelsen, O., 1995. Stratigraphic


correlation of late Palaeocene sand deposits in the SøgneBasin area of the Danish and Norwegian central North Sea.Terra Nova 7, 518–527.

Danielsen, M., Michelsen, O., Clausen, O.R., 1997. Oligocenesequence stratigraphy and basin development in the DanishNorth Sea sector based on log interpretations. Mar. Pet. Geol.14, 931–951.

Day, G.A., Cooper, B.A., Andersen, C., Burgers, W.F.J.,Rønnevik, H.C., Schoenig, H., 1981. Regional seismic struc-¨

Ž .ture maps of the North Sea. In: Illing, L., Hobson, V. Eds. ,Petroleum Geology of the Continental Shelf of NorthwestEurope. Heyden & Son, pp. 76–85.

Dinesen, A., Michelsen, O., Lieberkind, K., 1977. A survey of thePaleocene and Eocene deposits of Jylland and Fyn. Geol.Surv. Den., Ser. B 1, 1–15.

Dunoyer de Segonzac, G., 1970. The transformation of clayminerals during diagenesis and low-grade metamorphism: areview. Sedimentology 15, 281–346.

Galloway, W.E., Garber, J.L., Liu, X., Sloan, B.J., 1993. Se-quence stratigraphic and depositional framework of the Ceno-zoic fill, Central and Northern North Sea Basin. In: Parker, J.,

Ž .Parker, J.R. Eds. , Petroleum Geology of Northwest Europe:Proceedings of the 4th Conference, London. pp. 33–43.

Hakansson, E., Petersen, S.S., 1992. Geologisk kort over den˚Danske undergrund. Varv, Copenhagen.

Heilmann-Clausen, C., 1995. Paleogene aflejringer overŽ .danskekalken. In: Nielsen, O. Ed. , Danmarks Geologi - fra

Kridt til i dag. Aarhus Geokompendier. pp. 69–115.Japsen, P., 1993. Influence of lithology and neogene uplift on

seismic velocities in Denmark: Implications for Depth Conver-tion Maps. Bull. Am. Assoc. Pet. Geol. 77, 194–211.

Japsen, P., 1998. Regional velocity–depth anomalies, North SeaChalk: a record of overpressure and neogene uplift and ero-sion. Bull. Am. Assoc. Pet. Geol. 82, 2031–2074.

Jensen, L.N., Michelsen, O., 1992. Tertiær hævning og erosion iSkagerak, Nordjylland og Kattegat. In: Dansk Geologisk

˚Forening Arsskrift for 1990–91, pp. 159–168.Jensen, L.N., Schmidt, B.J., 1992. Late Tertiary uplift and erosion

in the Skagerrak area: magnitude and consequences. NorskGeol. Tidsskrift 72, 275–279.

Jordt, H., Faleide, J.I., Bjørlykke, K., Ibrahim, M.T., 1995. Ceno-zoic sequence stratigraphy of the central and northern NorthSea Basin: tectonic development, sediment distribution and

Ž .provenance areas. Mar. Pet. Geol. 12 8 , 845–879.Jordt, H., Michelsen, O., 1992. Seismic sequence stratigraphic and

structural analyses of the Cenozoic in the eastern North Sea.In: CENOS-Project. Department of Earth Sciences Universityof Aarhus, Denmark, p. 76.

Larsen, H.R., 1993. En sedimentologisk undersøgelse af SøvindMergelen samt det yngste Lillebælt Ler i Østjylland. Unpub-

˚lished Msc thesis,University of Aarhus, Arhus, 220 pp.Laursen, G.V., 1995. Foraminiferal analyses of Tertiary deposits

in the North sea Area: stratigraphy, palaeontology and taxon-omy. Unpublished PhD thesis, University of Aarhus, 276 pp.

Liboriussen, J., Asthon, P., Tygesen, T., 1987. The tectonicevolution of the Fennoscandian Border Zone in Denmark.Tectonophysics 137, 21–29.

Martini, E., 1971. Standard Tertiary and Quaternary calcereousŽ .nannoplankton zonation. In: Farinacce Ed. , Proceedings of

the II Planktonic Conference, Roma. pp. 739–785.Michelsen, O., 1994. Stratigraphic correlation of the Danish on-

shore and offshore Tertiary successions based on sequencestratigraphy. Bull. Geol. Soc. Den. 41, 145–161.

Michelsen, O., Danielsen, M., Heilmann-Clausen, C., Jordt, H.,Laursen, G., Thomsen, E., 1995. Occurrence of major se-quence stratigraphic boundaries in relation to basin develop-ment in Cenozoic deposits of the southeastern North Sea. In:

Ž .Steel, R., Felt, J., Johannesen, L., Mathieu, P. Eds. , Se-quence Stratigraphy: Advances and Applications for Explo-ration and Producing in North West Europe. NorwegianPetroleum Society, Elsevier, Amsterdam, pp. 415–427.

Michelsen, O., Thomsen, E., Danielsen, M., Heilmann-Clausen,C., Jordt, H., Lauersen, G.V., 1998. Cenozoic sequencestratigraphy in the eastern North Sea. In: de Graciansky, P.C.,

Ž .Jacquin, T., Vail, P.R. Eds. , Mesozoic–Cenozoic SequenceStratigraphy of Western European Basins. Soc. Econ. Palaeon-tol. Mineral. Spec. Pub. 60, pp. 91–118.

Nielsen, O.B., 1994. Lithostratigraphy and sedimentary petrogra-phy of the Paleocene and Eocene sediments from the Harreborehole, Denmark. Aarhus Geosci. 1, 15–34.

Nielsen, O.B., Sørensen, S., Thiede, J., Skarbø, O., 1986. Ceno-zoic differential subsidence of North Sea. Bull. Am. Assoc.Pet. Geol. 70, 276–298.

Sørensen, J.C., Gregersen, U., Breiner, M., Michelsen, O., 1997.High-frequency sequence stratigraphy of Upper Cenozoic de-posits in the central and southeastern North Sea areas. Mar.Pet. Geol. 14, 99–123.

Spjeldnæs, N., 1975. Palaeogeography and facies distribution inthe Tertiary of Denmark and surrounding areas. Norges Geolo-giske Undersøkelse 316, 289–311.

Ter-Borch, N., 1990. Geological map of Denmark. Structural mapŽ .of Top Chalk Group 1:500.000 . Geol. Surv. Den., Map Ser.,

7.Thomsen, E., 1995. Eocene and Oligocene calcareous nannofassil

biostratigraphy in the Linde-1 and Borg-1 boreholes. EFP-92project: Basin development of the Tertiary of the CentralTrough with emphasis on possible hydrocarbon reservoirs.Unpuplished report for the Danish Energy Agency. Report no.19. Department of Earth Sciences, University of Aarhus andDanish Geological Survey, Copenhagen, Denmark.

Ulleberg, K., 1987. Foraminiferal zonation of the DanishOligocene sediments. Bull. Geol. Soc. Den. 36, 191–202.

Vejbæk, O., 1997. Dybe strukturer i danske sedimentære bassiner.Geologisk Tidsskift 4, 1–30.

Vejbæk, O.V., Andersen, C., 1987. Cretaceous–Early Tertiaryinversion tectonism in the Danish Central Trough. Tectono-physics 137, 221–238.

von Salis Perch-Nielsen, K., 1994. Neogene and Paleogene cal-careous nannofossils from the Harre borehole, Denmark. In:

Ž .Nielsen, O. Ed. , Lithostratigraphy and Biostratigraphy of theTertiary Sequence from the Harre Borehole, Denmark. AarhusGeoscience, pp. 45–53.

Ziegler, P.A., 1990. Geological Atlas of Western and CentralEurope. Elsevier, Amsterdam, 239 pp.

geological indications for palaeogene uplift in the eastern north sea basin

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