Geological aspects of the Danish North Sea sector. With a report on the wells Dansk Nordsø E-1, E-2, F-1, G-1, H-1, I-1, J-1 and K-1

.......... . ........................................ . . 4 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Investigations by the Geological Survey . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Progress in the knowledge of the geology of the Danish North Sea sector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Structural survey of the Danish North Sea sector . . . . . . . . . . . . . . . . . . 8 Description of the wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Dansk Nords0 E-1 ........... . .... .. . . .. . . . ....... .. . . .. .. .. 21 Dansk Nords0 E-2 . ..... . ................... . ............... 29 Dansk Nords0 F-1 .......... ... .............................. 33 Dansk Nords0 G-1 .. .. .. ........... . ............. . .......... 40 Dansk Nords0 H-1 .... . . .. . .... .. . ........ .. ................ 47 Dansk Nords0 I-1 .......... . ................................ 52 Dansk Nords0 J-1 ....... ... . . .............. ...... ... .... . . .. 57 Dansk Nords0 K-1 .......................................... 63 Appendix: Some comments on the planktonic foraminifera-zonation of the North Sea Danian, by Inger Bang . . .... ....... ... .... ........ 70 Acknowledgements ........................... . ... .... .. ....... 80 Dansk sammendrag .... .. . . ................. ....... .. . ........ . 81 References ..... . .... . ..................... . . ... .... . .. ... .... 83


Introduction
Our knowledge of the geology in the North Sea Region is increasing constantly in present years because of the intensive exploration works in progress. Hundreds of wells are being drilled and thousands of kilometres of seismic lines shot. Though the Danish sector of the North Sea forms only a minor part of the North Sea area as a whole, the exploration of this part of the sea yields a comprehensive and valuable contribution to a geological understanding of the whole region.
In continuation of the publications on the Danish North Sea wells, introduced in 1974 by the survey of the Dansk Nords0 A-1 , A-2, B-1 , C-1 and D-1 wells, the Geological Survey of Denmark (Danish: Danmarks Geologiske Unders0gelse, abbreviated in the following text as DGU) here presents some geological results from another set of wells. These are the Dansk Nords0 E-1 , E-2, F-1, G-1 , H-1, 1-1 , J-1, and K-1 wells, drilled in the years 1968-1970. The DOU feels it reasonable to publish these results, even though it has not yet been possible to carry out profound investigations of all the geological and geophysical material that has been received from the Concessionaire. Many of the results presented here are new to the public and they are especially considered to be of some importance for the geological discussions. It must be noted that all references to unpublished internal reports are printed in italics, while references to publications are printed in roman types.
Concerning the exploration work and its organization, reference is made to the publication on the first 5 Danish North Sea wells (Rasmussen 1974 , p. 5 ff.) . In the period 1968-1970, as was the case in the foregoing years, the geophysical work was done by Gulf's survey ship »Gulfrex« and by Geophysical Services Intercontinental Limited . All 8 wells reported here were drilled from the platform »Mrersk Exploren< (cf. Rasmussen 1974 , p. 8, fig . 2) . D .G .U. Ill. rk . nr. 44

Investigations by the Geological Survey
The following report is mainly based on laboratory examinations in the Department of Subsurface Geology at the DGU. The lithological evaluations were made by describing the samples, and only to a limited extent in connection with studies of petrophysical logs. Some more conspicuous log features were taken into consideration, however.
In contrast to the first 5 Danish North Sea wells, no geologists from the DGU were stationed on the drilling platform (see Rasmussen 1974, pp. 6-7) during the drilling of the 8 wells described here. All samples and other data were forwarded to the DGU by the concessionaire . The institute has furthermore received monthly and half-yearly reports including geological and technical information. They have all been used in the following report on the 8 wells.
Due to varying degrees of diagenesis of the sediments and the nature of the sedimentary environment, it has not always been possible to obtain well-preserved fossils from the samples. The micropaleontologists have therefore had varying working conditions for their studies. Some sequences were easier to divide biostratigraphically than others, while yet others were impossible to handle. This heterogeneity must be taken into account together with the fact that many other geological tasks had to be executed by the same staff during the time of the examinations.
The comments on the quality of the samples and depth estimates, which were given in relation to the publication of the first five Danish North Sea wells, are also valid in the present context (see Rasmussen 1974, pp. 9-10).
As was the case in the previous publication, the log-verified depth figures are printed in italics. It is furthermore important to be aware of the fact that all depths in metres are calculated from sea level, whilst all depths in feet (usually printed in brackets) are measured from the kelly bushing.

Progress in the knowledge of the geology of the Danish North Sea sector
Since the last report on Danish North Sea wells in 1974, a number of contributions to the geology of the North Sea have been published. The majority of these are collected in the volume edited by A. W. Woodland, containing the geological lectures given at the London Conference in 1975 . An outline of the geological history of the whole area was given at the conference by P. A. Ziegler and W. H. Ziegler, and P. A. Ziegler recently revised his outline in the first issue of GeoJournal (1977). Reference is here made to this article as a good up to date background for more detailed studies on North Sea geology, including the Danish sector.
Publications since 1974 giving contributions to the geology of this sector are rather few . First of all may be mentioned the paper by Childs and Reed (1975) on the geology of the Dan Field and the Danish North Sea. Palynological and lithological information on the Upper and Middle Triassic in the Dansk Nords0 A-2, F-1 , and K-1 wells was given by Bertelsen (1975), while in his treatise of 1975 Michelsen gives a detailed stratigraphical interpretation of the Lower Jurassic section of the Dansk Nords0 F-1 , K-1 , and J-1 wells. A short survey with abbreviated logs of all wells drilled in the Danish sector until September 1975 was printed in Danish by Michelsen in 1976b, formerly published in December 197 5 as part of a report from the Danish government's supervision of the Concessionaire's activities.
Studies of the Jurassic formations in the Danish part of the Danish-Norwegian Basin, including maps, well sections, lithological descriptions and chronostratigraphy, have been made by Michelsen (1976aMichelsen ( , 1978a . Similar studies on the Upper Triassic formations have been carried out by Bertelsen (1978a), who has also investigated the Carboniferous in the Dansk Nords0 P-1 well and published his results together with other geological information on the well sequence (Bertelsen 1978b ).
Other printed contributions to the geology are the studies by Frost (1977) on the lineaments in the Danish region, including a "map of the major structural elements at the base Zechstein level". Madsen (1975) gave an outline of the geothermal gradient for the whole of the Danish area based on borehole temperature calculations from 13 wells.
In total, all these publications mark a step forward in our knowledge of the geology of the Danish sector. The majority of the results of the investigations, D .G . U. III . rk. nr. 44 Srructural survey however, are recorded in many internal (unpublished) reports. A number of these have formed the basis for the following descriptions of the eight North Sea wells.

Structural survey of the Danish North Sea sector
The great quantity of seismic data, together with geological analyses of borehole data and regional studies, has contributed to a more detailed mapping of the structural pattern of the Danish North Sea. J. C. Baartman, of the geophysical staff of the DGU, has compiled the more important structural feature s on an outline map (1976), which is shown in fig . 1.
In constructing such maps it will always be difficult to include structures of different ages on the same map. In the present case the mapping concentrated primarily on the more pronounced features attached to the pre-Upper Permian surface. However, the many salt-structures caused by halokinesis of the Upper Permian evaporite salt beds are of such importance to the tectonic picture of the Danish area that it was felt necessary to include them .
The resulting map thus depicts the more important or distinct structural deformations of the Paleozoic strata. The main regional Danish provinces are well known and comprise: 1. The Ringk0bing-Fyn High 2. The Danish-Norwegian Basin 3. The North German Basin 4. The Central Graben ( earlier named "East Dogger Bank Graben" ).
Though the 8 wells described in this paper are located in only two of these provinces, it seems appropriate to give a rev_iew of all four.
The Ringk0bing-Fyn High This pronounced regional high, stretching east-west across the Danish offshore and onshore areas, from the island of M0n in the east to the central North Sea in the west, has been known for many years as the Ringkobing-Fyn High. It has also been named the Fyn-Grindsted High, e.g. in Hey brook et al. 1967 , but the first mentioned name has been so well accepted in the literature that it would be difficult to replace it with another, better, and probably shorter one.
The high is no continuous regional structure. It is undoubtedly divided into separate blocks by intervening troughs or grabens. In the Danish North Sea at least 2 or 3 blocks can be separated: 1. The East North Sea Block, 2. The Holmsland Block and 3. Parts of the Grindsted Block.
The East North Sea Block forms the most westerly unit of the Ringk0bing-Fyn High. It is incompletely known geologically, as no wells have hitherto been drilled in the block, but to judge from seismic shootings, older Paleozoic metamorphics or Precambrian basement is present, in places at 3000 m or possibly even deeper.
Upper Permian deposits are probably absent throughout most of the block, and the Mesozoic sequence is reduced, especially with regard to the Triassic-Jurassic series of strata (cfr. Childs &Reed 1975, p. 12 , f. 4, andMichelsen 1978a).
The Holms/and Block is another unit, situated immediately west of the west coast of Jylland and separated from the East North Sea Block by the Horns Trough. It is separated from the next block to the east, the Grindsted Block, by a less pronounced trough.
The Grindsted Block is mostly restricted to the onshore southwestern part of Jylland, but its most westerly part extends to the nearby parts of the North Sea. Precambrian basement rocks have been proved to exist in its subsurface in a well at the town of Grindsted , where gneiss was found at 1599 m (Sorgenfrei & Buch 1964, p. 49). Seismic evidence points to a location of the basement surface at approx. 1800-2000 m in the vicinity of the town of Ringk0bing, close to the west coast of Jylland on the same block (Sorgenfrei 1966). On the Holmsland Block itself, only a few seismic lines have been shot and no wells have been drilled. The depth to the basement in this block seems to be about 3000 m, with a reduced Lower Mesozoic cover.
The Horns Trough separating the East North Sea Block and the Holmsland Block is probably a graben, and therefore is often designated the Horns Graben. Its boundary to each of the blocks is characterized by normal faults, the most pronounced of which form a fault system to the west. The basement can be expected at depths of about 5000 m, and the surface of the pre-Upper Permian seems to be dipping in a westerly direction. Information (see Michelsen 1976b, p. 127, f. 5) about the sequence at the center of the trough is given by the Dansk Nords0 R-1 well, which was abandoned in Lower Permian volcanics below reddish shales. No Upper Permian was found in this well. Triassic beds lay directly on the Lower Permian, and the Jurassic-Lower Cretaceous sequence was very thin. This was also the case with the Dansk Nords0 S-1 well, drilled in the continuation of the trough south of the Ring-k0bing-Fyn High. The Triassic in this well was not penetrated even after drilling nearly 2000 m. , from 1574 m to the total depth of 3780 m. It thus seems likely that the main subsidence of the Horns Trough took place during the Triassic.
The geological conditions in the trough between the Holmsland Block and the Grindsted Block are poorly known . The basement may occur at depths of the order of 4000 m, and results from seismic shootings suggest that a thick series of Palaeozoic deposits rest on the basement.

The Danish-Norwegian Basin
The main portion of the Danish area is covered by the sedimentary sequences of a large basin, filling the region between the Westland Arch and the Sele High to the WNW, the Fennoscandian Shield to the N, the Fennoscandian Border Zone to the NE and the Ringk0bing-Fyn High to the S (see fig . 2. from Michelsen 1978a) .
This basin is named the Danish-Norwegian Basin or the Norwegian-Danish Basin. A major part of the basin was earlier known as the Danish Embayment. This name is now replaced by the term : The Danish Subbasin.
The geological history of this subbasin has been studied for many years and it must be expected that its continuation towards the NW -below the sea bottom west of Northern Jylland -presents almost similar geological conditions as for the subsurface of NW-Jylland and the Limfjord Region.
This part of the sector is structurally characterized by many salt structures: domes as well as pillows.
The salt dome province of this part of the country continues in a westerly direction and includes the major part of the Danish North Sea sector north of the Ringk0bing-Fyn High and south of the pronounced fault-system , the Fjerritslev Fault , running NW from the Limfjord area and crossing the Danish-Norwegian sector border.
The pre-Upper Permian structural pattern is marked by numerous faults and minor grabens or blocks. It is especially worth mentioning that the fault forming the most westerly limit of the Horns Trough can be followed north-eastwards through the basin . How far north it can be traced is doubtful. The Dansk Nords0 C-1 well, described earlier (Rasmussen 1974, pp. 25-30), is placed close to this fault and was stopped in a Paleozoic trachyte. Other Paleozoic -probably Lower Permian -volcanics were found at the bottom of the D-1 well and in the R-1 well in the Horns Trough (Michelsen 1976b, p. 127, f. 5.). It is possible that the Permian volcanism known from the Oslo Region in Norway, the Danish-Norwegian Basin and the Horns Trough is part of the same province.
Another characteristic feature of this part is the thick Mesozoic sequence . The thickness of the Triassic deposits is especially pronounced. They can amount to more than 5000 m in the depocenters, but thicknesses of about 3000--4000 m can be expected in the wider central area of the basin.
The Jurassic sequence shows thicknesses of up to 1200 m. The depocenter is situated in North Jylland (Michelsen 1978a), almost in the same local area as where the Lower Cretaceous depocenter may occur. These last-mentioned deposits may exceed 700 m in total thickness . Another feature shows the Upper Cretaceous, of which the thickest series is found in a NW-SE striking belt across Denmark (see Stenestad 1972, p. 66, fig. 2), where it may exceed 2000 m .
All three wells in the Danish-Norwegian Basin reported on in the present paper, Nords0 F-1, J-1 , and K-1, were drilled on structures the development of which was more or less influenced by salt movements. The F-1 well was drilled in the east flank of a salt pillow, while the location of the J-1 well is on the crest of another salt pillow situated close to the Fjerritslev Fault on its down thrown eastern side. The K-1 well was placed on a third dome-like structure, whose pre-Mesozoic geology is less well known .

The North German Basin
South of the Ringk0bing-Fyn High, the so-called North German Basin stretches out to the south, in the Danish area covering the islands of Lolland and Falster, the South Fyn archipelago, the southern part of South Jylland , and the southwestern part of the Danish North Sea sector.
The geological conditions in the Danish part of this basin are known from geophysical and geological investigations carried out in connection with oil exploration in the years 1947-1959 . In the most northerly part of Germany, Hecht, v. Helms & Kehrer (1955)  The »block« probably continues below the eastern North Sea both in the German and Danish sector. Besides the southern continuation of the Horns Trough there are only two main structural areas in the Danish sector south of the Ringk0bing-Fyn High: one west of the trough and one east of it. They may both be of the same geological nature as the West-Schleswig Block and its Danish continuation . No wells have hitherto been drilled in these parts of the Danish North Sea sector, and the geophysical records are limited too. Only very few, minor faults have been marked on the map ( fig. 1).
On the German side a few wells have been drilled , but only very little geological information has been published so far. One of these wells, the onshore Westerland l on the north tip of the island of Sylt, may be representative for the area flanking the southern limit of the Ringk0bing-Fyn High. The profile of the well has not yet been published, but some restricted information is found in a few journal notes (Erdol und Koble, 19. Jahrg. 1966, p. 480 ;American Ass. Petr. Geol. Bull. , vol. 50, no. 8, 1966, p. 1645.
The well was abandoned in 3945 , 5 m in so-called »Precambrian phyllite « below Lower Permian »fine-grained sandstone, siltstone and claystone« from 3319-3843 m.
Corresponding occurences of probably low-metamorphic older Paleozoic rocks with a high degree of diagenesis have been found in the Danish onshore wells Aabenraa No. 1 and H0nning No. 1 in South Jylland, and similar rocks may perhaps occur below Permian beds in the southeastern part of the Danish North Sea sector.

Central Graben
The most important structural feature in the Danish North Sea sector, seen from an economic point of view , is the Central Graben. The term graben is sustained in this context because of its adoption into the geological vocabulary concerning the North Sea. It may be a subject for discussion whether the feature really is a graben, strictly speaking. In the Danish sector, however, it is evident that its eastern boundary up to the Ringk0bing-Fyn High is characterized by a normal fault or fault-system of relatively great order of size. The displacements amount to 5000 m or more.
The main features of the structural conditions in the southern half of the Danish part of the Central Graben are shown in 7 cross-sections, prepared by J. C. Baartman and L. Madsen of the geophysical staff of the DG U. These cross-sections are rendered in figs. 4-11 and they have been worked out from seismic lines, close to which wells have later been drilled. The locations of the Dansk Nords0 E-1 , E-2, G-1 and H-1 wells, together with the previously published wells (Dansk Nords0 A-1 and A-2), are shown on the sections.  It appears from the cross-sections that the pre-Permia n subcrop, which forms the floor of the graben, mostly fluctuate s between 6000 m and 7000 m below sea level.
It seems evident that a pattern of faults dominates the structural picture of the pre-Upper Permian in the Graben. Some of these faults are undoubtedly older than Uppe r Permian , and it seems probable that the underlying basement has been split up into minor blocks.
In the western part of the Central Graben there is a structural high , the  .:: .., " '~ northern part of which is situated in the Danish sector. This high, named the Dagger High , appears to have a relatively narrow and elongated shape directed NW-SE, almost parallel to the western edge of the Ringk0bing-Fyn High and the axis of the Central Graben. The proximity of the Dagger High can be traced on the left side of cross-sections D-D', C-C' and A-A', where the pre-Upper Permian reaches depths of between 5000 and 6000 m. The Dansk Nords0 P-1 well, drilled on the northern prolongation of the high in 1973, penetrated 62 m of metamorphic » greenstone« of late Silurian age (Bertelsen 1978a) below the depth of 3394 m below sealevel. This points to a Caledonian origin for the core of the Dagger High.
No wells have been drilled yet in the East North Sea Block. It is therefore impossible to judge whether the older Paleozoic of the block is Caledonian folded or not. It seems likely, however, that the pre-Carboniferous or pre-Devonian of the Central Graben area is Caledonian folded .
Only few of the faults found in the Central Graben could be shown on the structural map ( fig. 1). Other structural features are associated with the halokinesis in the Upper Permian sequence. Some 8 salt domes and a couple of salt pillows are shown, but additional structures are probably present. The halokinesis must also be responsible for the varying thicknesses of the Upper Permian Zechstein beds.
Resting on these strata a thick sequence of Mesozoic sediments is present all over the Central Graben. The total thickness amounts to approximately 5000 m. In cross-sections C-C' and D-D' the main part of these beds is of Jurassic age, while further south, in the Danish part of the Graben, the Triassic reaches a considerable thickness too.
The Lower Cretaceous sequences throughout are mostly thin in relation to the Triassic and the Jurassic, but the Cenozoic sediments are again characterized by great thicknesses. The variations are seen in the cross-sections. A wireline core was cut from 2720'-2876' with 28' of recovery.

Description of wells
A total of 48 Schlumberger sidewall cores were taken at different levels in the interval between 8183' and 13140'.
The following descriptions are mainly based on studies of the cuttings and the cores, carried out and reported by  Clay, grey, downwards with beds of sand. In places with numerous shells of molluscs.

Stratigraphical remarks
Upper Jurassic: In the samples from 10100'-13398' (3041-4047 m) Christensen (1974) found specimens of the ostracod genera Galliaecytheridea and Mandelstamia. No typical Lower or Upper Kimmeridgian species were found. The beds concerned can only be dated as of Kimmeridgian age, but Portlandian strata are probably also present. This, however, has not yet been proved.
Foraminifera are also present in the samples. In the samples from 13220'-13398' numerous specimens of Ammobaculites were found, but detailed studies are still lacking.
Upper Cretaceous: The sa mples from the Upper Cretaceous have yielded a poor foraminiferal fauna, the shells of which are often badly preserved. It has therefore been difficult to carry out a biostratigraphical investigation . Stenestad (197 4) has thus o nly been able to make the following preliminary subdi- The boundary betwee n the Danian and the Selandian seems to be found at 20 16 m (6735') (Bang 1974a).
The remaining Paleocene is overlain by the Eocene tuff bed series, the bottom of which is indicated at 1999 m (6680') on the gamma ray curve.
Middle Oligocene strata are probably prese nt down to about 1837 m (6150'), where Haplophragmoides walteri appears for the first time (Dinesen 1974).
It is open to doubt whether Upper Oligocene beds are found in this well or not. The lower boundary of the Miocene is placed where the first specimen of Sigmoilina tenuis is found in the samples. This occurs at 1645 m (5520') .
The deposits above this depth and up to 566 m (1980') belong mainly to the Miocene, but it can not be precluded that Upper Oligocene beds are included in the sequence. The boundary between the Middle Miocene (Hod-28 D.G.U. Ill . rk. nr. 44 de Formation) and the Upper Miocene (Gram Formation) is found on the gamma ray log to be present at 1237 m (4180'), while the Pliocene/ Upper Miocene limit is placed at 566 m (1980') on the basis of foraminiferal data (by Kristoffersen 197 4). The Upper Miocene section in this boring is 671 m thick, which is more than ever shown earlier in Danish North Sea wells.
Tertiary: All known Tertiary stages are found, but further studies are needed before the depths of the boundaries between them can finally be determined. The following preliminary subdivision is proposed: From the logs, the top of the Danian section can be placed at 1959 m (6550') and the bottom of the ash-bearing series of the Eocene at 1952 m (6525'), the total thickness of the Selandian thus being only 7 m (25').
The samples from the Eocene sequence have been inspected by Dinesen (1974), who points to the occurrence of many specimens of the agglutinating Haplophragmoides walteri in the cuttings below 1746 m (5850').
The overlying Miocene series has not yet been subdivided in detail, but the Middle Miocene/ Upper Miocene boundary, as defined on gamma ray logs from the earlier Danish North Sea wells (Rasmussen 1974) was in the present boring found at 1261 m (4260'). Kristoffersen (1974) is at present of the opinion that Upper Miocene beds are present up to 621 m (2160'), covered by marine Pliocene (Scaldisian) sediments.
Quaternary: Foraminiferal investigations by Buch (1974a) are the basis for the following subdivision: 41-344 m Undated beds 344-454 m Icenian 454-475 m Amstelian 475-517 m Undated beds Buch (I.e.) defines the Quaternary/Pliocene limit by 1) the presence of Elphidium oregonense above 4 75 m and the absence of this species in the samples below, 2) by a distinct change in the foraminiferal assemblages at 475 m and 3) by a characteristic peak on the SP and resistivity logs. Pliocene foraminifera are only observed in the samples below 484 m.
The subdivision of the Quaternary series is mainly based on 1) the pre-

F-1
Other miospore assemblages were recovered by the same author (Bertelsen 1975, p. 25) in the sandstone from 2078-2118 m. The species include abundant Ricciisporites tuberculatus Lundblad and as accessories were found Densosporites foveocingulatus Schulz, Aratrisporites spp. and Rhaetipollis germanicus Schulz. Bertelsen (Joe. cit. p. 26) correlates the beds containing this microflora with the Upper Rhaetian. For further discussions on the pre-Jurassic sequence, reference is made to Bertelsen's paper.
The sandstone from 2041-2049 m and the shale from 2049-2078 m are both referred to the Gassum Formation. The age of this formation can be either Jurassic or Triassic.
Lower Jurassic: Above the Gassum Formation a quite uniform series of dark shales or claystones, referred to the Fjerritslev Formation, is penetrated. Michelsen ( 197 5,  between these zones, but the thickness of the Kimmeridgian part seems to amount to about 125 m. Lower Cretaceous: The foraminiferal content of the Lower Cretaceous sequence has been studied by Buch. Only the five uppermost samples yielded faunas which were of value for age determinations. The following preliminary subdivision into stages appears from Buch's (1975) and Christensen's (1974)  The uppermost boundary of the Danian unit probably lies at ea. 667 m (2310'), since Bang (1974c) found planktonic foraminifera of Danian age in the sample at 2310'. The top of the limestone is, however, found at 694 m (2400') .
Superposing the Danian, some beds of Paleocene age occur containing, amongst other species, many specimens of Spiroplectammina spectabilis. A boundary to the Eocene volcanic tuff beds is visible on the gamma ray log at 652 m, while other Tertiary units can hardly be recognized from the Schlumberger logs.
The Eocene sequence contains strata whose characteristics are well known from Danish onshore sections. However, it has still not been possible to find a distinct boundary between the Eocene and Oligocene beds in this well. D .G.U. Ill. rk. nr. 44 F-1 and G-1 Dinesen (1974) mentions that the Oligocene sequence probably consists of Middle Oligocene beds. The foraminiferal species Turrilina alsatica is very common here and is reminiscent of the fauna in the Middle Oligocene Viborg Formation known from the Danish onshore. Other characteristic fauna! elements are Ceratobulimina contraria and numerous "Dentalina".
The upper part of the brownish micaceous and glauconitic silt from 63-13 7 m may be of Upper Oligocene age. It contains Asterigerina guerichi, and it seems most likely that no Miocene or younger Tertiary beds are present in this boring.
Quaternary: Only 3 samples (from 256'-330') can be considered of Quaternary age. They contain a few Quaternary foraminifera (Buch 1974a). In the sample 300'-330' Upper Oligocene species such as Sphaeroidina variabilis and Nonion affine are also present. They are probably derived from the underlying layers.

Chronostratigraphy
The following subdivision is based on internal reports by Buch, Dinesen, Bang, and Christensen: The Kimmeridgian is mainly represented by the Galliaecytheridea spinosa Zone, which seems to be of considerable thickness. Above the Upper Kim-G-1 meridgian there occurs a less than 100 m thick series of Portlandian comprising the Galliaecytheridea compressa Zone. (Christensen J 974).

49-415 m Quaternary
A detailed biostratigraphical subdivision of the Upper Jurassic in this boring must wait until more thorough investigations have been carried out.
Lower Cretaceous: A subdivision of the Lower Cretaceous section and determination of the limit to the Upper Jurassic was made by   In cuttings samples from 6520', 6550' and 6580 ' Bang (1974 d) has found agglutinating foraminifera, characteristic of the non-calcareous Paleocene clay (Spiroplectammina spectabilis Assemblage).
The Eocene-Oligocene boundary in this boring is not well defined. Dinesen (J 974) has inspected some of the samples and found specimens of the foraminifera Haplophragmoides walteri in the sample 5860'-5890', but single specimens of the same species occurred already in sample 5290'-5320' , and it is not obvious that the species is restricted to the Eocene.
It is not precluded that beds of Upper Oligocene age are present, but as a whole the section from 1603 m (5380') to 415 m (1484') is of Neogene age. The base of the Upper Miocene sequence as defined on the gamma ray log is found in this well at 1147 m (3884'). The deposits below this depth and down to 1603 m (5380') are mainly of Middle Miocene age, probably including Lower Miocene beds.

Chronostratigraphy
The chronostratigraphical subdivision of the drilled section of this borehole is based on investigations by Buch (J 974 a), Kristoffersen (1974) Dinesen (1974, Bang (1974 e) , andStenestad (1974). Their results can be summarized as follows:

554-2002 m Tertiary 2002-2127 m Upper Cretaceous
Stratigraphical remarks H-1 Upper Cretaceous. The Upper Cretaceous series in this borehole seems to be rather reduced in relation to onshore Danish Cretaceous series. It has not been possible to determine the limit between the Danian and the Maastrichtian because of the lack of samples from the interval 6683 '-6708 ' , within which the limit must be found.
A preliminary stratigraphical subdivision of the Upper Cretaceous section by Stenestad (1974), based on the foraminiferal remains, shows the following  Lower Cretaceous: A preliminary investigation by Buch (1975 a)  The remaining Paleocene has not been further subdivided into chronostratigraphical units. A few specimens of Spiroplectammina sp. and other agglutinating foraminifera characterizing the Selandian have been shown to occur in the samples below 2688 m (8940') .
The Eocene sequence is introduced by the base of the tuff-bearing beds at 2688 m (8940'), and in the Lower Eocene strata in this boring a planktonic foraminiferal fauna is present, containing amongst other species Globigerina patagonica, known from the Lower Eocene R0snres Clay of Denmark (Dinesen 1974). The first occurrence of G. patagonica was recorded at 2642 m (8790').
The uppermost occurrence of the agglutinating species Haplophragmoides walteri is found at 1746 m (5850'), this depth presumably being close to the top of the Eocene.
Typical Middle Oligocene forms such as Turrilina alsatica and Rotaliatina bulimoides are recognised above 1746 m (5850'), and the topmost specimens of Sigmoilina tenuis have been recorded at 1691 m (5670'). According to Schlumberger correlation the top of the Middle Oligocene section is indicated as lying at 1654 m (5550').
It is a question whether Upper Oligocene beds are present or not in this boring. The sequence above 1654 m (5550') and up to 1462 m (4920') is mainly of Middle Miocene age, but the faunas from this section have not yet been studied in detail. An important boundary at 1465 m (4927') is, however, indicated on the Schlumberger logs. This is the Middle Miocene -Upper Miocene limit or, more exactly, the boundary between the Hodde Formation and the Gram Formation.
The Miocene -Pliocene boundary is found at about 603 m (2100'). The samples from 511-530 m (1800'-1860') contain specimens of Pseudoeponides pseudotepidus, which may indicate that beds of Pliocene age are present in the boring.
Quaternary: The 450 m thick Quaternary sequence is divided by Buch (1975 b) into the following units:

Chronostratigraphy
The following chronostratigraphical subdivision is based partly upon publications by Michelsen ( , 1978a, Bertelsen (1978a)  The well-defined Gassum Formation is, however, clearly present to judge from the gamma ray and the I.T.T. logs. This formation is partly Upper Triassic and partly Lower Jurassic of age (see Bertelsen 1978a and. Lower Jurassic: The sequence above 1697 m has been investigated by , who subdivides the marine claystone from 1074-1697 m biostratigraphically into 3 ostracod zones (Michelsen, and refers the whole interval to the Fjerritslev Formation (Michelsen 1978a Middle Jurassic: It is evident from the wireline logs that the middle Jurassic Haldager Formation is present from 1055-1074 m. Only very few non-characteristic fossils have been recorded from the samples. It has therefore only been possible to date the sandy deposits in the interval on the basis of the log-correlations (Michelsen 1978a).
Upper Jurassic: The interval between the Lower Jurassic and the Lower Cretaceous has been inspected for ostracods by Christensen, who gives the following comments in his internal report (1975)  The depth figures given by Christensen all originate from the labels of the cuttings samples. They do not correspond to log depth figures and therefore need to be corrected. However, they give an impression of the succession of important ostracod species in this particular well, and they furthermore indicate the presence of the chronostratigraphical units mentioned.
Lower Cretaceous: A preliminary subdivision based on the foraminiferal fauna is given by Buch (1975b) Quaternary: No Tertiary beds have been identified in this borehole. Above the chalk only two samples were available (from 60-79 m). They contained 7 and 11 specimens respectively of Quaternary foraminifera, together with a few Upper Cretaceous forms. Buch (J 975b) considers this combination to have originated from glacigene sediments.

Occurrence of hydrocarbons
No oil or gas was found in this boring.

Lithological log
The following description is based on the preliminary investigations of the cuttings, carried out in the laboratory by Bertelsen, Jacobsen, Kristoffersen and Michelsen (internal report, dated August 1970

Chronostratigraphy
The following chronostratigraphical subdivision has been prepared on the basis of internal reports by Bertelsen, Christensen, Michelsen, Buch, Stenestad, Bang and Dinesen and, for the lower part of the boring, from publications by Bertelsen (1975Bertelsen ( , 1978a and Michelsen ( , 1978a.  (1975, 1978a) with the Haldager Formation of Denmark (defined by Larsen 1966) and in consequence are probably of Middle Jurassic age. The beds above 1383 m contain ostracods, which were preliminarily studied by Christensen (J 975) . The foraminifera in the samples from around the limit between Jurassic and Lower Cretaceous were furthermore investigated by Buch (1975b ). A combination of the views of these two geologists results in the following preliminary chronostratigraphical subdivision: Upper Cretaceous: The samples from the Upper Cretaceous section are highly contaminated by foraminifera from the beds above and are thus difficult to use as a safe basis for a stratigraphical subdivision. Nevertheless, Stenestad (1975a) has succeeded in establishing a preliminary chronostratigraphy for these beds: Resting on the Maastrichtian chalk occurs a white limestone with a valuable foraminiferal content. Bang (1975b) has been able to find evidence for the two foraminiferal zones into which she subdivides the North Sea Danian biostratigraphically ( see fig. 15, p. 71):

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The Globoconusa daubjergensis Zone (top to be found in the sample interval 1620 '-1650' (457-466 m)) and the Subbotina triloculinoides Zone. The top of the Danian is probably to be found in the sample interval 1380 '-1410' (383-393 m) , where an assemblage used to define the top of the Danian occurs together with an assemblage characterizing the Selandian marl (Kerteminde Marl) found in eastern onshore Denmark. The lithology in this boring is thus an example, among others, that the Danian sedimentation is not only restricted to the white limestone.
The top of the Selandian can be placed either at 382 m, just below the volcanic tuff beds (age: probably Eocene), or a little higher, at 374 m, because Paleocene foraminifera seem to occur in the sample 1350'-1380' (374-383 m) (Dinesen 1974). The only trace of a possible Eocene foraminiferal fauna is the dominant occurrence of Glomospira charoides in the sample 1320 '-1350' (365-374 m).
Above 365 m micaceous clays with Turrilina alsatica are present, pointing to a Middle Oligocene age. It can not be precluded, however, that the lower part of the section is represented by Eocene sediments which lack microfossils of Eocene age, but are filled with Oligocene foraminifera deriving from the overlying beds due to caving.
Upper Oligocene, Miocene, and Pliocene sediments do not seem to be present in this boring.
Below this marine series the sediments contain a contamination of Upper Cretaceous, Tertiary, and Quaternary foraminifera, as is often the case in boulder clay.

Occurrence of hydrocarbons
No oil or gas was found in this boring. Specimens from the Eoglobigerina eobulloides Subzone within the Globoconusa daubjergensis Zone. The picture gives a selection of the rich variety of species forming the assemblage. The lowermost Danian, e.g. as described by Bang in 1971 , was not stated to be present in the Danish North Sea sector at the time when the report by Bang was finished (1974) . Fig. 17. Dansk Nords0 A-2. Ca. 6093' Specimens from an assemblage zone (preliminarily named the "Sandby-assemblage") within the Globoconusa daubjergensis Zone . Among the species pictured are Turborotalia sp. 3 (= cf. reissi, Bang 1962) in the lower right corner and Planorotalia compressa in the upper right corner. Specimens of Globoconusa daugbjergensis are seen in the upper left part of the picture, showing a great variation of types, morphological as well as in relation to size.    Varying specimens of Globorotalia uncinata from the Subbotina triloculinoides Zone, in a typical so-called " Klintholm-assemblage" of Denmark.

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Specimens from the Globorotalia sp. 5/6 Zonule of the Subbotina tri/oculinoides Zone. Reference is made to Bang 1969. In the right-hand column of specimens the species Planorotalia compressa s. l. is seen.