Biostratigraphy and Paleoceanography of the Cretaceous Seaway Between Norway and Greenland

Earth-Science Reviews 46Ž. 1999 27±98 www.elsevier.comrlocaterearscirev

Biostratigraphy and paleoceanography of the Cretaceous seaway between Norway and Greenland

F.M. Gradstein a,), M.A. Kaminski b, F.P. Agterberg c a Saga Petroleum, KjorboÕeien 16, N-1302 SandÕika, Norway b KLFR, 3 Boyne AÕenue, Kendon, NW4 2JL, UK c Geological SurÕey of Canada, Ottawa, Ontario, Canada

Abstract

The narrow seaway between Greenland and Norway, in Cretaceous time was over 1500 km long and 300q km wide, and partly of bathyal water depth during Aptian through Campanian. It received a large volume of fine-grained, siliciclastic sediments, with intercalated, gravity-flow sandstone wedges. As a conduit for heat transport between the low latitudes and polar region, Atlantic watermasses particularly affected the eastern, Norwegian margin of this seaway. Despite its high-latitude setting, calcareous and few siliceous planktonic microfossils thus play an important role in regional stratigraphy and facies analysis, and a majority of fossil events correlate to NW European basins. The eastern margin sedimentary succession may be subdivided in several broad lithologic units:Ž. 1 Thin, multicolored, marly sediments of Hauterivian±Bar- remian age, with a shallow marine Falsogaudryinarnodosariidrostracod assemblage;Ž. 2 Dark mudstones and minor sands, Aptian-early Cenomanian in age, with an upper bathyal, agglutinated assemblage, and monotypic Hedbergella floods;Ž. 3 Thick mudstone facies with thin, slope-apron turbidite sands, and an impoverished benthicrplanktonic assemblage of late Cenomanian±Coniacian age, deposited in an upper bathyal, oxicrdysaerobic environment. Where Turonian sedimentation rates are low, a planktonic foraminiferal assemblage with Whiteinella, Hedbergella, Dicarinella, and Marginotruncana occurs;Ž. 4 Grayish, laminated mudstones, Santonian±Campanian in age, with local sands in the north, a low diversity, middle to upper bathyal benthicrplanktonic foraminiferal assemblage, and an Inoceramus prisms and radiolarianrdiatom flood; a Campanian agglutinated foraminiferal bloom also is known from the Atlantic oceanic realm;Ž. 5 More marly sediments of Maastrichtian age, with a low diversity planktonicrbenthic foraminiferal assemblage. Using the distribution of 1755 foraminiferal and dinoflagellate microfossil events in over 30 exploration wells, a RASCŽ. Ranking and Scaling probabilistic zonation served as a template to build a Cretaceous zonal model with 19 assemblage and interval zones, including over 100 events. Variance analysis ranks 72 events according to reliability in correlation. Three new index taxa include UÕigerinammina una and Ammoanita globorotaliaeformis Ž.Albian , and Fenestrella bellii ŽCampanian . . Widespread planktonic flood events occur in late Albian through early Cenomanian, early±mid Turonian, late Santonian±earliest Campanian and mid-Maastrichtian, the result of northwards shifts of warmer water masses, and disruptions in water stratification in the dysaerobic basins. An earliest Cretaceous hiatus separates Jurassic from Cretaceous strata. Ongoing block-faulting, coupled to thermal subsidence and global sealevel rise increased water depth in Aptian±Albian time from neritic to bathyal, and created sand accommodation space in dysaerobic, restricted settings. In Cenomanian±Coniacian time, sedimentation rates in the `central basin' increased 10-fold, whereas paleo waterdepth did not deepen. This relatively brief

) Corresponding author. Tel.: q47-67-126-141; Fax: q47-67-126-585; e-mail: [email protected]

Ž.less than 10 m.y. tectonic episode, resulting in deposition of deep water sands, is tentatively linked to stress re-orientation in the Rockall area. A widespread upper Maastrichtian±Danian hiatus, the result of `shoulder' uplift, reflects `break-up', prior to the onset of Paleogene seafloor spreading in the Norwegian Sea. q 1999 Elsevier Science B.V. All rights reserved.

Keywords: Norway; Greenland; Cretaceous seaway; quantitative foraminiferal zonation; petroleum stratigraphy

1. Introduction ous and siliceous planktonic microfossils, thus play an important role in regional stratigraphy and facies This study is an attempt to better understand the analysis. The virtual absence of endemic fossil taxa Cretaceous seaway between Greenland and Norway indicates open watermass connections to the adjacent from a paleoceanographic and paleontologic point of seas and ocean. Widespread planktonic flood events view. Impetus for this effort derives from data un- occur in late Albian±early Cenomanian, early to earthened by ongoing drilling for hydrocarbons along middle Turonian, late Santonian±earliest Campanian the eastern margin of this seaway, on average buried and mid-Maastrichtian. An agglutinated foraminiferal more than 2 km deep. No detailed reconstructions bloom occurs in Campanian time, related to a similar exist of this seaway from presumed paleo coastline bloom in the Atlantic Ocean. Many Cretaceous fossil data, but Fig. 1a,b gives a schematic overview for events can be correlated to the Atlantic and west two Cretaceous time slices, using reconstructions of Tethys regions. the paleogeographic positions of the European and Despite extensive offshore exploration for oil and North American plates prior to opening of the gas for over two decades, there is no published Labrador Sea, regional seismic, sparse outcrop, and documentation of the Cretaceous microfossil record sparse well data. From this data, it appears that this in Norwegian wells. A concise and detailed docu- seaway was narrow and longitudinal, over 1500 km mentation would be of regional benefit, and would long and 300q km wide. Similarity between Upper greatly assist ongoing exploration, not only as a Triassic±Jurassic formations on East Greenland and means to stabilize opinions, but also as a catalyst to offshore mid-Norway also argue in favour of their continuous stratigraphic improvements and refine- relative proximityŽ. T. Saether, pers. commun., 1997 . ments. The Neocomian foraminiferal record in As we will argue, this seaway was relatively shallow a small outcrop on Andoya, northern Norway compared to the Cretaceous Atlantic Ocean south- was described by Lùfaldi and ThusuŽ. 1979 , while ward, but certainly upper and temporally also middle Nohr-HansenŽ. 1993 documented Lower Cretaceous bathyal. Depocentres in this seaway received large dinoflagellate stratigraphy, onshore East Greenland. volumes of fine-grained siliciclastic sediments, with Study of the mid Cretaceous foraminiferal record in intercalated, gravity-flow sand wedges. some wells and outcrops is presently underway at As a conduit for heat transport between the low Oslo University, and University College, London. latitudes and polar region, Atlantic watermasses par- To better understand the microfossil record, this ticularly affected the eastern, Norwegian margin of study documents biostratigraphic data in wells be- this seaway. Despite its high-latitude setting, calcare- tween 608 and 678N, along the eastern margin of the

Fig. 1.Ž. a,b Schematic paleogeographic reconstruction of North Atlantic and Norwegian Sea in late NeocomianŽ a; late Hauterivian±Bar- remian.Ž and in middle Cretaceous b; approximately Cenomanian . time, showing the deep marine, bathyal passage Ž. in dark blue between Norway and Greenland. Purplesoceanic, abyssalŽ. south of the Charlie Gibbs fracture zone , dark bluesmiddle to upper bathyal, lighter bluesmarine, neritic, graysland; Wd refers to the marginal marine Wealden facies; circum Norwegian Sea siliciclastŽ. sand facies is not shown. Deep marine connections into the Barents Sea are uncertain, as are various highs shown in the proto Norwegian Sea. From Barremian through Cenomanian time, transgressions progressed, and particularly since middle Albian time flooded the Bohemian Massif and other German landmasses, while land adjacent sand wedges shrank. The widespread floodingŽ. Figs. 2 and 3 , probably combined with fault tectonics enhanced graben formation offshore Norway, increasing sand accommodation space. There are no indications for deep water connectionsŽ. middle to upper bathyal in Aptian±Cenomanian time through an easterly passage via Germany towards the Polish Carpathian Trough. Ongoing transgression during Cenomanian±Turonian time removed a wide rim of Early Cretaceous siliciclastsŽ yellow coloured sand-prone wedges.Ž around the NW German Basin J. Mutterlose, pers. comm., 1998 . . F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 29 30 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Norwegian seaway. Its mid-Cretaceous latitude may Norwegian sea from a modest micropaleontological have been 58 or more further southŽ e.g., Dore, perspective. As with all first attempts to describe the 1991. , but still well in the boreal biofacies realm. regional paleontology±biostratigraphy, and place it We have attempted to place prominent microfossil in a paleoceanographic framework, this is a first pass appearances and disappearances in a paleoceano- at the data. The information gathered, and the inter- graphic context, and interpret paleobathymetry and pretations will have to be continuously improved burial history. The biostratigraphy used herein de- upon, and emended as temporal and geographical rives from a combination of deterministic and proba- coverage of the Cretaceous sediments is incremen- bilistic models; this combination is more reliable tally broadened. than a purely subjective zonation only, and brings Below, a brief paleoceanographic and sedimen- out stratigraphically important properties of the data, tary setting is provided, followed by Stratigraphic not otherwise accessible. Data and MethodsŽ. Section 3 , Taxonomy Ž Section Conventionally, biozonal schemes for petroleum 4.Ž. , Biostratigraphy Section 5 , Variance Analysis exploration portray the temporal and spatial distribu- and PaleoceanographyŽ. Section 6 , Paleobathymetry tion of fossil events for the purpose of well to well and Sequence BreaksŽ. Section 7 , and Subsidence correlations, using also log and seismic data. Most and SedimentationŽ. Section 8 . Appendix A is a emphasis is on colourfull displays of wells with catalogue of approximately 250 foraminiferal taxa, manyŽ. not crossing correlation lines of fossil events, observed by us in the Cretaceous strata, offshore presumably representing time lines. Rarely, attention Norway, whereas Appendix B describes the three is given to the broader paleogeographic and paleo- new index species. Three plates portray the three ceanographic setting that may clarify why fossil newly described index taxa, and the hedbergellid events actually occur, or are absent. Not uncom- blooms. Much more work is needed to provide monly, a relative sealevel curve is strung along the atlas-type coverage of the hundreds of taxa, that will fossil record in time, without actually achieving in- stabilize taxonomy and improve subsurface stratigra- sight, unless burial histories and regional hiatusses or phy and paleobathymetry. facies breaks also are considered. Hence, a more elaborate approach is warranted with events in the context of burial rates and regional geology. In this study we will try to link to paleoceanography, bios- 2. Cretaceous paleoceanographic and sedimentary tratigraphy and burial history. setting Paleoceanography is an interdisciplinary field of study, with many aspects that need to be deciphered, including paleobiogeography, geochemistry and plate The following statement is quoted verbatim from tectonics. This study is only a small attempt to Larson et al.Ž. 1993 , as it helps to place the Creta- achieve some paleoceanographic insight into the ceous seaway in a wider paleoceanographic context.

Fig. 2. Generalized Cretaceous stratigraphic history, offshore mid Norway, showing distribution of common hiatussesŽ. hatched diagonally and deeper marine, gravity flow sandsŽ. in yellow . To the right of the figure is the generalized paleobathymetric trend Ž. in blue , periods of dysaerobiaŽ. semi-restriction of watermasses and shelly microfossil plankton flooding events. The latter are of importance in the regional stratigraphy. Both the BarremianrAptian unconformity, and the widespread mid-Cenomanian hiatus and seismic reflector may be in common with similar features in the Mesozoic sedimentary wedge, offshore Newfoundland and Labrador. This circum-Atlantic resemblance in gross tectono-stratigraphic features points to a common cause, probably linked to plate-tectonic re-organisation. Following a universal hiatus separating shallow marine upper Jurassic from shallow marine CretaceousŽ. upper Hauterivian±lower Barremian , the area steadily deepened to upper bathyal paleo waterdepth in mid-Cretaceous, and middle to upper bathyal in Campanian, followed by uplift induced shallowing in Maastrichtian. Hiatusses are more widespread in upper Barremian±middle Albian than in Upper Cretaceous strata. Plankton flood events occur in upper Albian±mid Cenomanian Ž.Hedbergella delrioensis and H. planispira , Santonian±lowermost Campanian Ž.ŽInoceramus prisms and radiolarians and also in lower Maastrichtian Globigerinelloides Õolutus and Rugoglobigerina rugosa .. Watermass restrictions are most widespread in Albian and Campanian time, when deep water agglutinated foraminifers flourished. F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 31

A paleoceanographic view clarifies the depositional of greenhouse climates, featuring reduced tempera- history of the siliciclast strata, in the roughly south± ture gradients from the equator to the poles, general north running gateway between the Atlantic and absence of polar ice caps, and oceans at least 13 C ArcticŽ. Fig. 1a,b . ``The mid-Cretaceous was a time warmer than the present ones. Oceans were elevated 32 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 to extremely high stands of sea levels, and were mid-Cretaceous North Atlantic Ocean, south of the more susceptible to development of oxygen deficits, Charlie Gibbs fracture zone clearly stands out. It is expressed in various ways. Not only were black interesting that, although mid-Cretaceous deep water shales more widespread, but specific `anoxic events' agglutinated foraminiferal assemblages, offshore were recorded by condensed oil-shale sequences in Norway bear similarity to flysch-type assemblages widely separated parts of the world, linked by global from the Carpathian TroughŽ. see below , no `direct' isotope anomalies. Conditions were particularly deep marine connection is envisaged between these favourable for petroleum generation: more than half regions via the NW German Basin. Biota exchange of our present petroleum reserves appear to have most likely took place via the North Atlantic and been generated during this episode, which includes Tethys. Aptian time, and peaked either in the Albian, as The Cretaceous sedimentary succession in the generally believed, or in the Cenomanian. Bauxites area under consideration may reach several kilome- and laterites were widespread, testifying not only to ters in thickness and basinward is buried under a tropical climates, but also to widespread, tectonically Cenozoic mudstone `blanket' of 2±3 km. It may be driven uplifts and emergences.'' subdivided in several broad units listed below; litho- Although the equitable climate hypothesis in Cre- stratigraphic assignments follow the scheme in Dal- taceous time is under active discussionŽ e.g., Sell- land et al.Ž. 1988 . wood et al., 1994. , there is abundant evidence for Ž.1 Thin, multicolored, marly sediments of late global anoxic events and high sealevels. The deposi- Hauterivian through early Barremian age, becoming tion of dark shales, relatively updip, in sub-basins dark coloured upwards, where the paleoenvironment along the southwestern and western margins offshore changed from oxic to dysaerobic. The foraminiferal Norway, clearly is related to widespread transgres- microfossil assemblage, listed in Appendix A under sion along the continental margins during the high the heading Hauterivian±Barremian, contains com- stands of mid-Cretaceous sea levels, sluggish water- mon Falsogaudryina and nodosariids; ostracoda also mass circulation and run-off high in organics. are common, reflecting mostly shallow marine Fig. 1a shows a schematic paleogeographic recon- Ž.neritic conditions. The sediments belong in the Lyr struction of NW Europe for late Neocomian time Formation of the Cromer Knoll Group. Ž.late Hauterivian±Barremian , and Fig. 1b show a Ž.2 Dark mudstones and minor sands, Aptian± schematic one for middle Cretaceous timeŽ ap- early Cenomanian in age, with deep water aggluti- proximately Cenomanian. . Landmasses are in grey, nated foraminifers and monotypic Hedbergella the neritic seaway is light blue, the bathyal seaway is floods. Foraminiferal taxa present are listed under dark blue. During Barremian time, the NW German the heading Aptian-Albian in Appendix A. The sedi- Basin, in the lower half of the sketch map of Fig. 1a, ments belong in the Lange Formation of the Cromer was severely restricted, with an opening towards the Knoll Group, and were laid down in an upper bathyal proto-Norwegian Sea only. Barremian sediments, environment, with a dysaerobic deeper watermass offshore Norway, also are relatively restricted and Ž.Fig. 2 . thin, if at all present. Ž.3 Thick mudstone facies with thin, slope-apron From Barremian through Cenomanian time, trans- turbidite sands, with a locally impoverished benthic gressions progressed, and particularly since middle assemblage deposited in an upper bathyal, oxicrdys- Albian time flooded the Bohemian Massif and other aerobic setting, of late Cenomanian±Coniacian age German landmassesŽ. Kemper, 1973 , while land ad- Ž.Fig. 2 . The sandy sediments are assigned to the jacent sand wedges shrank. Widespread flooding Lysing Formation of the Cromer Knoll Group. Since since Albian timeŽ. Figs. 2 and 3 , probably com- these sands form a disjunct set of gravity flows, not bined with fault tectonics that enhanced graben for- mappable as a continuous unit, the name Lysing mation offshore Norway, increased sand accommo- Member would be more appropriate. Where Turo- dation spaceŽ. see Section 8 . The postulated bathyal nian sedimentation rates are low, a relatively rich connection from the Norwegian±Greenland Seaway planktonic foraminiferal assemblage may occur with through the Scotland±Greenland gateway to the Whiteinella, Hedbergella, Dicarinella and Margi- F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 33

Fig. 3. Cretaceous well sections studied for foraminiferal biostratigraphy and paleobathymetry. In black-stratigraphic section drilled; in blue-section studied in ditch-cuttings samples; in red-section studied in core samples. Note the limited stratigraphic coverage in Lower Cretaceous, when hiatusses were widespread.

notruncana ŽAppendix A, Cenomanian±Turonian Ž.5 Marly sediments of Maastrichtian age, with a section. , yielding marly sediments. low diversity planktonic and benthic foraminiferal Ž.4 Grayish laminated, mudstones, Santonian± assemblage. Locally, and particularly southward, the Campanian in age, with local sands in the distal planktonics may occur in floodsŽ. Fig. 2 , with mono- Voering basin, offshore mid-Norway, have a mostly typic Rugoglobigerina and Globigerinelloides ŽAp- low diversity, middle to upper bathyal foraminiferal pendix A, Coniacian±Maastrichtian section. . The assemblage, an Inoceramus prisms peak, and a radi- sediments are grouped in the Springar Formation of olarianrdiatom floodŽ Appendix A, Coniacian± the Shetland Group. Maastrichtian section. . The sediments belong in the Cretaceous lithostratigraphy of the wells to an Kvitnos to Nise Formations of the Shetland Group. extent depends on knowing the age of rocks, and in 34 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 that sense is not an independent descriptor. The latter ceous sand prone intervals. The bulk of samples is is not surprising given the widespread presence of from ditch cuttings, which forces use of last occur- relatively monotonous mudstone facies. Although renceŽ. LO events, and last consistent or last com- sediment units may stand out on physical well logs, mon occurrenceŽ. LCO events. The emphasis on biostratigraphy is an essential tool when drilling, and events warrants a discussion of some of their strati- when attempting to correlate wells. graphic peculiarities. A paleontological record is the position of a fossil taxon in a rock sequence. The stratigraphic range of a fossil is a composite of all its records. The end- 3. Stratigraphic data and methods points of the range are biostratigraphic events, which includes the first occurrenceŽ appearance in time or In order to arrive at an understanding of the entry.Ž and last occurrence disappearance from the temporal distribution of Cretaceous microfossil geologic record or exit. . A biostratigraphic events is events, a biostratigraphic zonation was constructed, the presence of a taxon in its time context, derived followed by variance analysis of the fossil events. from its position in a rock sequence. The fossil During this exercise, benefit was derived from the events are the result of the continuing evolutionary Ranking and ScalingŽ. RASC method of biostratigra- trends of Life on Earth; they differ from physical phy. events in that they are unique, non-recurrent, and Principal wells that contributed to the Cretaceous that their order is irreversible. zonation, offshore Norway, are from north to south: Often first and last occurrences of fossil taxa are 6610r3±1, 6610r3±1R, 6607r5±2, 6607r5±1, relatively poorly defined records, based on few spec- 6607r12±1, 6507r2±1, 6507r2±2, 6507r2±3, imens in scattered samples. Particularly with time- 6507r6±2, 6507r7±1, 6507r7±2, 6506r12±5, wise scattered last occurrences, one may be suspi- 6406r2±1, 36r1±2, 35r3±1, 35r3±2, 35r3±4, cious that reworking has locally extended the record, 35r3±5, 35r12±1, 35r11±2, 35r11±5, 35r9±1, reason why it is useful to distinguish between last 35r9±2, 35r10±1, 34r7±21, 34r7±21a, and occurrenceŽ. LO , and last common occurrence 30r3±1. In addition, we took into account the much Ž.LCO . condensed, but cored Lower Cretaceous interval in The shortest spacing in relative time between the 33r9±15 well, in the vicinity of the 30 and 34 successive fossil events is called resolution. The block wells. greater the probability that such events follow each Wells are strung-out roughly in a north±south other in time, the greater the likelihood that correla- zone along the continental margin, offshore Norway, tion of the event record models isochrons. Most between 608 and 668NŽ. Brandshaug et al., 1997 . On industrial data sets make use of sets of LO and LCO the paleogeographic map of Fig. 1b, the wells would events. In an attempt to increase resolution in stratig- occur in that part of the bathyalŽ. dark blue zone, raphy, particularly when many sidewall cores are that extends northward, just NW of the letter N of available, efforts sometimes are made to recognize Norway, towards mid-Norway, and immediately west up to five events along the stratigraphic range of a of its siliciclast rim. The latter encloses the Nordland fossil taxon, including last stratigraphic occurrence Ridge, an important feature for westward sediment Ž.`top' or LO event , last common or consistent oc- shedding, in the deep marine Cretaceous basin currenceŽ. LCO event , last abundant occurrence Ž.Blystad et al., 1995; Saether et al., 1997 . Ž.LAO event , first common or consistent occurrence Data admitted in the analysis are from released Ž.FCO event and first occurrence Ž. FO event . Unfor- well completion reports, strongly augmented with tunately, such practise may not yield the desired inhouse re-analysis of original slides or re-processed increase in biostratigraphic resolution sought after, ones, with emphasis on the foraminiferal fossil frac- for reason of poor event traceability. tion. A majority of wells was re-studied by us in Event traceability is illustrated in Fig. 4, where some detail, including sidewall coreŽ. swc , and core cumulative event distribution is plotted against num- samples. Cores are largely confined to mid-Creta- ber of wells for the Cretaceous data set under consid- F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 35

duced that microfossil groups with higher local species diversity, on average have lower event traceability. Data sets with above average traceability of events are those where one or more dedicated observers have spend above average time examining the fossil record, verifying taxonomic consistency between wells or outcrop sections, and searching for `missing' data. In general, routine examination of wells by consultants for drilling completion reports yields only half orŽ. much less of the taxa and events than may be detected with a slightly more dedicated approach. Over 90% of the mentioned increase in events is due to more detailed analysis of the foraminifers, a relatively neglected microfossil group in the Cretaceous subsurface, offshore Norway. There are other reasons than lack of detail from analysis why event traceability is relatively low. For example, lateral variations in sedimentation rate change the diversity and relative abundance of taxa in coeval samples between wells, particularly if sam- Fig. 4. Cumulative frequency of event occurrences versus number pling is not exhaustive, as with well cuttings or of wells for the Cretaceous, offshore Norway. There are 518 sidewall cores. It is difficult to understand why fossil events with 1746 records in 31 wells. The events stem from events might be locally missing. Since chances of dinoflagellates, foraminifers and few miscellaneous microfossils. The curve is asymptotic, showing an inverse relation between detection depend on many factors, stratigraphical, event distribution and the number of wells. None of the events mechanical, and statistical in nature, increasing sam- occur in all wells; clearly, far fewer events occur in five or six pling and studying more than one microfossil group wells than in one or two wells, and hence the cumulative fre- in detail is beneficial. quency drops quite dramatically with a small increase in number Although not always admitted or clarified, bios- of wells. Obviously, the majority of fossil events have poor traceability, which is true for most data sets, either from wells or tratigraphy relies almost as much on the absence, as from outcropsŽ. Gradstein and Agterberg, 1998 . Microfossil groups on the presence of certain markers. This remark is with higher local species diversity, on average have lower event particularly tailored to microfossils that generally are traceability. widespread and relatively abundant, and harbour stratigraphically useful events. Only if non-existence of events is recognized in many, well-sampled sections, may absences be construed as affirmative for eration. The events stem from dinoflagellates, stratigraphic interpretations. If few samples are avail- foraminifers, and several miscellaneous microfossils. able over long stratigraphic intervals, the chance to The curve is asymptotic, showing an inverse relation find long-ranging taxa considerably exceeds the between event distribution and the number of wells. chance to find short-ranging forms, unless the latter None of the events occur in all wells; clearly, far are abundant. In actual practise, so-called index fos- fewer events occur in five or six wells than only in sils have a short stratigraphic range, and generally one or two wells, and hence, the cumulative fre- are less common, hence easily escape detection, quency drops quite dramatically with a small in- reason why their absence should be used with cau- crease in number of wells. Obviously, the majority tion. of fossil events have poor traceability, which is true Two methods that assist with the regional bios- for most data sets, either from wells or from outcrops tratigraphy, are multiwell event bookkeeping and Ž.Gradstein and Agterberg, 1998 . These authors de- probabilistic zonation and correlation. For this pur- 36 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 pose we employed the computer programs Makedat, graphic calibration than a poorly documented, sub- Ranking and ScalingŽ. RASC and Correlation and jective zonation. True stratigraphic resolution im- Standard Error CalculationŽ. CASC . Details of these proves if event spacing in relative time is assessed methods are in a companion paper to this study with standard deviations, that create an understand- ŽAgterberg and Gradstein, 1999; see also Gradstein ing as to the chance that two events are superposi- et al., 1985. . As a point of interest, we might men- tional. In this study, a calculated zonation with error- tion that two other Cretaceous biostratigraphic stud- bars on most likely event positions will be used, and ies, of limited scope for the Danish sector of the a subjective one, which together best explain, and central North Sea, also used quantitative stratigraphic predict the stratigraphic distribution of the fossil methods. A Maastrichtian dinoflagellate zonation for record. the Dan FieldŽ. Schioeler and Wilson, 1993 , was assisted by the RASC method and StougeŽ. 1991 employed graphic correlation to better define the 4. Taxonomy biostratigraphic ranges of Upper Cretaceous calcareous foraminifers. Appendix A lists over 250 benthic and planktonic Traditionally, biostratigraphic zonations are exe- foraminiferal taxa identified during this study in the cuted `by hand' through a painstaking process of wells, grouped in the four broad time slices Hauteriv- Ž.mental stacking in relative geologic time of numer- ian±Barremian, Aptian±Albian, Cenomanian± ous fossil events from many different outcrop or well Turonian, and Coniacian±Maastrichtian. The selec- sections. Subtle stratigraphic order relationships are tion of the time slices reflect broad taxonomic evaluated, and frequent gaps are bridged by superpo- changes, the result of gradual evolutionary turnover, sitional hypothesis, where data are scarce. The hu- and local changes in Cretaceous paleoenvironment. man mind is good at evaluating observed and virtual In Appendix B, three new index taxa are dis- superpositional data and bridging data gaps. Unless a cussed, i.e., UÕigerinammina una n. sp. and Am- massive amount of documentation is provided with moanita globorotaliaeformis n. sp., both of the U. zonations, it may be difficult to trace back zonations una zone, late middle to early late Albian, and to the original data, and frequently the actual data are Fenestrella bellii n. sp. of the F. bellii zone, early not listed in a zonal report. This lack of reproducibil- Campanian. These new taxa are important elements ity in biozonation, particularly where exploration in the regional biozonation proposed in this study. biozonations are concerned, may lead to problems The taxonomy of Lower Cretaceous calcareous with chronostratigraphic calibration and high-resolu- benthic foraminifers adopted for this study, is based tion correlations of zonal events. to a large extent on well-known micropaleontologi- Quantitative methods of biostratigraphy, like cal studies of NW GermanyŽ Bartenstein, 1977a,b, graphic zonation and correlation, or Ranking and 1978, 1981; Bartenstein and Bettenstaedt, 1962; Scaling cannot easily match the subtilities of very Michael, 1966. . Supplementary data include studies detailed subjective zonations, based on many, often of the North SeaŽ Burnhill and Ramsay, 1981; King incomplete stratigraphic sections, using much infor- et al., 1989.Ž , western Siberia Komissarenko and mation on missing data. As mentioned above, the Belousova, 1990.Ž , the northern tethys margin Moul- experienced biostratigrapher uses almost as much lade, 1961; Weidich, 1990.Ž , Atlantic Canada Wil- information on absence as on presence of data, and liamson and Stam, 1988. , and studies based on Cre- the former cannot be evaluated by a method. To taceous DSDP SitesŽ. Riegraf and Luterbacher, 1989 . produce a data set that is detailed and informative For the agglutinated benthic foraminifers, the taxon- enough to yield quantifiable, high-resolution zona- omy in this study is based on Carpathian flysch tions is a considerable task. However, once such a assemblagesŽ Geroch and Nowak, 1984; Bubik, 1995; dataset and its derived quantitative zonation is ac- Neagu, 1965, 1972. and on more recent studies of complished, and made available together with its raw the Cretaceous of the North SeaŽ King et al., 1989; data and data processing details, it serves as a more Kaminski et al., 1995a,b. , and of the North Atlantic reliable model for correlation and chronostrati- Ž.Kuhnt and Kaminski, 1990, 1997 . F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 37

The taxonomy of Upper Cretaceous calcareous variation plus its spread. Similarly, population taxon- benthic foraminifers makes use of the study for the omy studies of Hauterivian±Albian Falsogaudryi- northern North Sea by King et al.Ž. 1989 , and to a nella and UÕigerinammina are desirable, to curtail lesser extent of the southern British Isles study by picking of extreme morphologies as taxa, and clarify- Hart et al.Ž. 1989 , and Czechoslowakia by Hanz- ing geographic variation in morphology. likovaŽ. 1972 . For planktonic foraminifers, good use Surprisingly, well reports often paid little atten- was made of the atlasses of StainforthŽ. 1981 and tion to planktonic foraminifers, that provide valuable Robaszynski et al.Ž. 1984 . Agglutinated benthic ties to standard Cretaceous zonations. A search for foraminiferal taxonomy and stratigraphy follows planktonic foraminifers in microfossil slides in many studies by Geroch and NowakŽ. 1984 , Kuhnt and wells yielded biostratigraphic events for Hedbergella KaminskiŽ. 1990 , Bubik Ž. 1995 , Coccioni et al. delrioensis, H. planispira, H. paradubia, H. hoelzi, Ž.1995 , and Kuhnt et al. Ž. 1998 , all dealing with Whiteinella spp., Dicarinella imbricata, D. hagni, deep marine assemblages. Praeglobotruncana spp., including P. stephani, and Dinoflagellate event data are included in this anal- Globotruncana. Rare Dicarinella concaÕata and D. ysis, as far as reported for the wells. Their optimum carinata, well-known indices for Coniacian±Santo- stratigraphic distribution, relative to the foraminiferal nian strata, but not previously recorded offshore events, is listed in the RASC optimum sequence Norway, were observed in wells of the 35 explo- zonation. Many of the palynological data were gen- ration blocks. In cores in well 33r9±15 we observed erated by Dr. Graham Bell, Stratlab. The dinoflagel- Aptian Blefusciana and middle Albian Globigerinel- late taxonomy benefitted from the study by Costa loides gyroidinaeformis, with the interval previously and DaveyŽŽ.. in Powell Ed. , 1992 . As recently being dated Barremian, using dinoflagellate taxa now pointed out to us by P. SchioelerŽ pers. comm., considered reworked in the condensed Lower Creta- 1998. , the taxon names Maghrebinia membra- ceous section in this well. niphora and Apteodinium grande used in this report, preferably should be renamed Cyclonephelium membraniphorum and Apteodinium maculatum subsps. 5. Biostratigraphy grande, respectively. A detailed search for taxonomic synonymies both 5.1. Introduction in foraminifers and dinoflagellates between well re- The biostratigraphy of Lower and Upper Creta- ports improved taxonomic consistency. For example, ceous foraminifers in NW Europe has been studied Tritaxia carinata in some wells was reported as T. by a number of authors since the 1960s. A review of dubia, and Caudammina o uloides as C. o ulum. Õ Õ the relevant schemes developed for the NW Euro- Many haphazard records of Hedbergella sp. and H. pean mudstone facies is useful in order to understand delrioensis LO were omitted as irrelevant events; the microfossil records from the eastern side of the Rugoglobigerina macrocephala was included in R. Norwegian Sea. Studies on rich and diversified mi- rugosa. In two wells, Endoceratium dettmaniae was crofossil material from both sides of the Norwegian recorded well below its reasonably expected occur- Sea, in progress at the University of Oslo and Uni- rence, and omitted. Chattangiella spinosa in some versity College London, will complement the present wells was renamed C. sp. 1Ž Bell, pers. comm., data compilation, and will increase insight in zonal 1996. , and U igerinammina bulimoides of some Õ and paleogeographic distributions. consultants is here named UÕigerinammina una n. sp. Biglobigerinella multispina was included in Glo- 5.2. Northwest Germany bigerinelloides Õolutus. Problems exist with the taxonomy in the plexus of Gaudryina filiformisrKar- The work from Bartenstein et al. on the benthic rerulina conÕersarGerochammina lenis, and with foraminifers of the Saxon Basin has lead to the various Gyroidinoides and GaÕelinella taxa. These publication of a detailed biostratigraphic scheme for plexa warrant further study, using populations of NW GermanyŽ. Bartenstein and Bettenstaedt, 1962 , specimens to describe mid-points in morphological and later to a proposal for a general biostratigraphic 38 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Table 1 Foraminiferal taxa found in the Lower Cretaceous, offshore mid Norway, that also occur in NW Germany Species Range in NW Germany Pleurostomella obtusa lower±middle Albian GaÕelinella intermedia lower±middle Albian ValÕulineria gracillima upper Aptian to upper AlbianŽ. max. upper Aptian Gaudryina diÕidens upper Aptian to lower AlbianŽ. max. upper Aptian GaÕelinella barremiana mid Barremian to lower AptianŽ. max. mid Barremian Reophax troyeri mid Barremian to mid AlbianŽ. max. upper Aptian±lower Albian Lenticulina ouachensis ssp. upper Hauteriv. to lower AptianŽ. max upper±mid Barremian Textularia bettenstaedti upper Hauteriv. to lower AlbianŽ. max. upper Aptian±lower Albian Lenticulina eichenbergi upper Valanginian to mid BarremianŽ. max. Hauterivian Epistomina hechti Barremian Falsogaudryina tealbyensis Valanginian±Barremian

zonation for the Lower Cretaceous using more cos- ever, Weidich's zonal scheme was only tentatively mopolitan taxaŽ. Bartenstein, 1978 . The biostrati- correlated to the standard chronostratigraphy, and graphic zonation of the NW German Lower Creta- calibration of Weidich's samples by means of plank- ceous was based on the stratigraphic succession of tonic microfossils is needed to refine the age of his 75 foraminiferal, and 12 ostracod species in middle zones. Table 2 gives a list of stratigraphically impor- Valanginian to lowermost Cenomanian of Saxony. tant cosmopolitan species from Weidich's study, that The stratigraphic ranges of benthic foraminifers were also occur in the Norwegian Sea assemblages. calibrated to the standard ammonite zones. The zonal The biozonation of Geroch and NowakŽ. 1984 , scheme mainly uses calcareous benthic foraminiferal and additions by Geroch and KoszarskiŽ. 1988 , pro- species more typical of shallow marine sediments, vide a reference frame for cosmopolitan deep-water such as Citharina, Epistomina, and ornamented agglutinated foraminiferal assemblages. The Lower Lenticulina. Unfortunately, neither of these genera is Cretaceous portion of their zonal scheme consists of common in the Cretaceous Norwegian Sea. Fewer 19 species and seven zones, and the Upper Creta- than 15 of the Northwest German index species were commonly encountered in this study. Of these, the 11 taxa occur consistently, and are used for chrono- Table 2 Foraminiferal taxa found in the Lower Cretaceous, offshore mid stratigraphic correlation, as listed in Table 1. Norway that also occur in the Alps in Germany and Austria Species Range in German Alps 5.3. Northern Tethys Margin Caudammina crassa Barremian to Cenomanian Kalamopsis grzybowskii Barremian to Cenomanian WeidichŽ. 1990 published a zonal scheme for the Textularia bettenstaedti Berriasian to Aptian Tithonian to Cenomanian based on his studies of the PlectorecurÕoides spp. upper Albian Northern Calcareous Alps in Bavaria and Austria. Trochammina quinqueloba upper Albian His scheme divides the Lower Cretaceous into 10 Gaudryina diÕidens Aptian to Albian zones, based on first occurrences or acmes of nomi- Spiroplectinata spp. Aptian to Albian Lenticulina busnardoi Berriasian to Hauterivian nate zonal taxa. Weidich's zonation is based primar- L. eichenbergi Valanginian to Barremian ily on calcareous benthic foraminifers, but because L. wisselmanni Barremian his studied sections were deposited in deep water, ValÕulineria spp. upper Aptian to Albian there is a greater possibility for correlation with the GaÕelinella barremiana Barremian to Aptian r Norwegian Sea region. Several of the index taxa are G. intermedia berthelini Aptian to Cenomanian Patellina subcretacea Berriasian to lower Aptian also found in the North Sea, which verifies Weidich's Falsogaudryina Ž.? tealbyensis Barremian±Aptian selection of taxa that are largely cosmopolitan. How- F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 39 ceous of 17 species and four zones. All the zones are 5.4. Central North Sea based on the first occurrence of index taxaÐso they are not equivalent to zones of the same name recog- Foraminiferal zonal schemes for the Lower and nised in other areas, and are not directly applicable Upper Cretaceous of the Central North Sea have to wells with cavings problems. Although these zones been informally proposed by a number of consul- were originally developed for the Carpathian flysch tants, but were not published. An exception is the deposits, parts of the Geroch and Nowak scheme biozonation developed by King et al. at Paleoser- apply to other deeper marine continental margins vices, that was published in 1989; it links to the with Cretaceous `flysch-type assemblages' as far detailed study by KochŽ. 1977 for the calcareous away as the NW Australian marginŽ Kaminski et al., upper Cretaceous of NW Germany. 1992.Ž , and the Pacific Riegraf and Luterbacher, King et al.Ž. 1989 has proposed two parallel 1989. . zonations for the North Sea, that subdivide the Lower Several of the nominal index species from this Cretaceous into 12 zones and subzones, and the zonal scheme have now been observed also in the Upper Cretaceous in 11 zones and subzonesŽ see Fig. Norwegian seawayŽ. Appendix A; Fig. 5 , including 6a,b. . The `FCS' zonal scheme has applications in Verneuilinoides neocomiensis, PseudoboliÕina Õari- the shelfŽ. chalk facies of the southern sector of the abilis, Pseudonodosinella troyeri ŽsReophax minu- North Sea, whereas the `FCN' zones are based on tus of Geroch and Nowak. , Haplophragmoides non- deeper-water taxa and can be used for the bathyal ioninoides, and Bulbobaculites problematicus,as shale facies in the northern and central sectors. The well as several other species from the range chart of FCN zonation scheme is most applicable to the study Geroch and NowakŽ. 1984 including Ammobacu- area, and the zonation, offshore Norway resembles loides carpathicus, Trochammina quinqueloba, this schemeŽ. Fig. 6a,b, and discussion below . The Trochammina abrupta, Thalmannamina neocomien- index taxa are normally widespread and common, sis, Caudammina crassa, Hippocrepina depressa, which makes the scheme quite robust. However, Kalamopsis grzybowskii, Gaudryina filiformis, Cau- little attention was paid to deep water agglutinated dammina oÕulum, Rzekina epigona, Tritaxia dubia foraminifers that become more important northward. Ž.sT. subparisiensis , Marsonella crassa and Doro- Below, we will discuss in detail similarities and thia oxycona. Many of these species have not been differences to the northern North Sea zonation. previously reported from the North Sea, and deserve more detailed taxonomic coverage than feasible in this study. 5.5. Cretaceous biozonation, offshore mid Norway An interesting point is that recognition, offshore Norway of many of the middle to Upper Cretaceous taxa, known well from the Polish Carpathian Trough, In this section we outline a Cretaceous biozona- and partial application of its bathyal±abyssal realm tion for offshore mid-Norway, largely using zonation, does not mean a direct deep marine con- foraminiferal taxa, and some miscellaneous micro- nection existed between the proto Norwegian Sea fossils. Rather than trying to create a zonation that and the Carpathian Trough region. As may be seen maximizes stratigraphic resolution, and often is diffi- on Fig. 1a,b, such a connection is not drawn in, and cult to apply over a broad region, we prefer to not likely for mid-Cretaceous time, given the string outline zonal units that are easy to correlate over the of relatively shallow marine deposits eastward into offshore region. Hence, use was made of the RASC Germany. Locally in the deepest part of the NW method to erect a zonation for the middle and upper German basin, bathyal conditions may have existed part of the Cretaceous, that also helped to integrate in Albian time, but such was not part of a deep dinoflagellate events in the biozonation. The lower passage eastwardŽ. J. Mutterlose, pers. comm., 1998 . Cretaceous, pre-Albian section is too fragmented Deep marine faunal exchange most likely took place Ž.Fig. 3 , and well coverage insufficient to effectively via the gateways from the proto Norwegian Sea into apply quantitative stratigraphic methods; that part is the North Atlantic. zoned subjectively. Below, we first will analyse 40 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

RASC results, prior to a discussion of the successive upper Cenomanian±lower Turonian zone, but in the Cretaceous zones, that build on and extend the RASC original well record that is not obvious. In most results. cases, reasons for the erratic stratigraphic positions Initially, the data set for RASC comprised the are not clear. multiple microfossil event record in 37 wells, mostly Despite filtering outŽ. removal of `bad' data from LO or LCO events of 550 foraminifers, some the RASC runs, 21 cycles needed to be broken prior siliceous microfossils and dinoflagellates, for a total to zonation, where groups of three or more events of 1873 records. After several intermediate zona- had an unresolvable stratigraphic order. In our expe- tions, using RASC and its normality testing functions rience with datasets from a variety of regions over of the event record, scores of records, five eratic the world, with different microfossils, 21 event cy- events, and seven wells with very low sampling cles is a low number. Inclusion of the 10 events that qualityŽ. partly due to turbo-drilling were deleted were deleted from the data set would have increased from the data. For example, the following fossil the number of cycles from 24 to 43, and the number event records were deleted, as being far too high, or events with of six or more stepmodel penalty points too low stratigraphically in wells, as determined from 14 to 36; out of placeŽ. AAA events events in from RASC stepmodel penalty points: Globorotalites the scattergrams also was higher, whereas the num- multiseptus in 34r7±24s, Endoceratium dettmaniae ber of out of place events using the RASC normality in 35r3±4, Gaudryina filiformis in 6507r6±2, Gy- test would have declined from 78 to 64, not a roidinoides beisseli in 34r7±22 and Hedbergella significant change, but possibly the result of a `more sp. in 6607r5±1; several LO events for dinoflagel- complete', although not more precise optimum se- late cyst taxa were changed into LCO events. In quence. addition, Rhaphidodinium fucatum, Heterohelix As mentioned, the few wells omitted from the globulosa, Caudammina oÕuloides, Dorothia tro- RASC run suffer from poor data coverage. The choides, Hedbergella sp., Dorocysta litotes, Xe- remaining 31 wells harbour 519 events, with 1755 nascus ceratoides, Florentinia mantelli, F. deanei records. Table 3 provides a summary of data proper- and F. ferox showed highly erratic occurrences ties and RASC results. Number of events in the through the wells, leading to deletion from the run optimum sequence with S.D.-ave. S.D., deals with data. From our own observations it is clear that the number of events that have a standard deviations Hedbergella sp. consistently occurs in the nominate below the average for the optimum sequence; the

Fig. 5.Ž. Right Optimum sequence of Cretaceous events Ž foraminifera, dinoflagellates, miscellaneous microfossils and one physical log marker.Ž. , offshore mid Norway, using the Ranking and Scaling RASC method on 1753 records in 31 wells. The arrow of time is upward. The majority of events are last occurrencesŽ. LO in relative time; LCO stands for Last Common or Last Consistent Occurrence. Each event occurs in at least six out of 31 wells, leaving 97 events. The display also shows the relative stratigraphic position of nine unique events. The optimum sequence is graphically tied to the scaled optimum sequence Ž.sRASC zonation to the left, largely using the nominate zone markers.Ž. Left Scaling in relative time of the optimum sequence of Cretaceous events shown in Fig. 5Ž. right . The arrow of time is upward; the interevent distances are plotted on the relative scale to the left in dendrogram display format Each event occurs in at least seven of the 31 wells, leaving 72 events. Sixteen stratigraphically successive interval zones are recognized, middle Albian through late Maastrichtian in age. Large breaksŽ. at events 52, 84, 205, 255 and 137 indicate transitions between natural microfossil sequences; such breaks relate to hiatusses or facies changes, some of which are known from European sequence stratigraphyŽ.Ž. see text for more details . 1 The una±schloenbachi break reflects a latest Albian lithofacies change and hiatus, connected to the Octeville hiatus in NW Europe.Ž. 2 The delrioensis LCO±brittonensis break reflects the mid-Cenomanian lithofacies change and hiatus, connected to the mid-Cenomanian non-sequence and Rouen hardground of NW European sequence stratigraphy.Ž. 3 The Marginotruncana±polonica break, above the level of Heterosphaeridium difficile LCO, which represents a maximum flooding surface, may be the turn-around in the middle Coniacian tectono-eustatic phase, near the end of the Lysing sand phase.Ž. 4 The bellii±dubia break, is again Ž near or . at a maximum flooding event, this time correlated to the LCO of T. suspectum in the early middle Campanian, above the change from marly sediments to siliciclasts at the base of the Campanian.Ž. 5 The dubia±szajnochae break reflects the abrupt change from siliciclasts to marly sediment at the Campanian±Maastrichtian boundary, only noted in the southern part of the region. F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 41 42 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

fact that 44 out of 72 optimum sequence events have a lower than average standard deviation is good. Stratigraphic coverage is relatively good, even that, as usual, only 98 out of 519 events occur in six or more wells, and only 72 events occur in seven or more wellsŽ. Fig. 4 . Cretaceous dinoflagellate cysts in particular show large taxonomic diversity, but limited traceability for many taxa. The Cretaceous optimum sequenceŽ. Fig. 5, right includes 98 eventsŽ. `tops' , spanning Hauterivian through Maastrichtian strata. The preferred scaled optimum sequence contains 72 events; in addition, nine events noted with UU occur in fewer than seven wells but are inserted for the purpose of zonal definition and chronostratigraphic calibration. The events listed are average last occurrencesŽ. average `top' , unless otherwise indicated; LCO stands for last common or last consistent occurrence, and FCO means first common or first consistent occurrenceŽ in an uphole sense. . The so called `Range' of taxa in the optimum sequence, which is a measure of the number of sequence positions an event spans Žsrank positions in Fig. 5, right. , is always low, except for Fromea sp. 2Ž. 5 rank positions , Dinopterigium cladoides Ž6 rank positions.Ž , Trithyrodinium reticulatum 5 rank positions.Ž. , Gyroidina beisseli 5 rank positions , Chatangiella niiga Ž.5 rank positions , and Chatang- iella sp.Ž. 10 rank positions . The last occurrence record for these taxa is not reliable for detailed correlations in the wells examined. The optimum sequence serves as a guide to the stratigraphic order in which events in wells are expected to occur, hence it is both predictive, and serves in high-resolution correlation, as outlined below. Fig. 5Ž. left side is the scaled optimum sequence for the Cretaceous in the 31 wells. Over a dozen stratigraphically successive RASC interval zones stand out, middle Albian through Maastrichtian in age, that guide the discussion of the 19 interval, acme and assemblage zones below. Reso- lution is poor in the lowermost and uppermost parts of the scaled sequence, and reflects lack of superpositional data, and condensation of `tops' in the uppermost and lowermost Cretaceous part of wells. The scaled optimum sequence shows major breaks Fig. 5Ž. continued . between several successive zones, including between F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 43 the una and schloenbachi zones, delrioensis LCO sis. Hence, the final zonation takes advantage of both and brittonensis zones, Marginotruncana and subjective, and more objective analysis, and inte- polonica zones, bellii and dubia zones, and particu- grates the two into one framework. larly between dubia and szajnochae zones. The The zones are named after prominent foraminiferal question what the meaning is of these large breaks, is taxa, that are easily recognized in the wells, and are best answered when we consider how RASC scaling relatively widespread. The zones are informal, and operates. Scaling calculates the relative stratigraphic their description is bound to change with addition of distance between successive events in the RASC more data, and further assessment of taxonomy. optimum sequence. This relative distance is calcu- Some of the foraminiferal index taxa ŽTrocholina, lated from the frequency of cross-over of all possible Blefusciuana, Globigerinelloides gyroidinaeformis, pairs of events in the optimum sequence over all Hedbergella brittonenesis, Marginotruncana coro- wells. Hence, large distances between successive nata and Dicarinella concaÕata. are rare due to the events, corresponding to the larger RASC zonal high-latitude setting of the study region, or poor breaks indicated above, signify strongly diminished preservation of carbonate tests in the siliceous mud- cross-over between events that occur below and stones. As mentioned earlier, integration, using the above the breaks. Reasons for these breaks thus must RASC method, with dinoflagellate events, improves be thought in stratigraphic gaps, and paleoenviron- the applicability of both types of microfossils for mental changes that likely are connected to sequence regional biostratigraphy. stratigraphic changes. The reasons will be discussed Chronostratigraphic assignments are tentative, in more detail below, but may be summarized as hampered among others by the absence, or scarcity follows: of keeled planktonic foraminifers, like Rotalipora, 1. the una±schloenbachi break reflects a latest Al- and the majority of Dicarinella, Marginotruncana, bian lithofacies change and hiatus, connected to and Globotruncana. Zones of short stratigraphic du- the Octeville hiatus in NW Europe. ration, like the Sigmoilina antiqua Zone, assigned to 2. the delrioensis LCO±brittonensis break reflects lower Cenomanian may be difficult to observe in the mid-Cenomanian lithofacies change and hia- ditch cuttings, particularly when the lithology is tus, connected to the mid-Cenomanian non-se- sandy. There is ample room for improving the reso- quence, and Rouen hardground. lution of the lower and upper parts of the zonation. 3. the Marginotruncana±polonica break may be the For example in the condensed Hauterivan±Bar- turn-around in the tectono-eustatic phase of mid- remian, and hiatus riddled Aptian±middle Albian dle Coniacian, near the end of the Lysing sand sections, and in the thick, carbonate devoid strata of deposition. The break occurs above the level of the inner Voering Basin, assigned to Campanian. Heterosphaeridium difficile LCO, which repre- The latter represents a poorly sampled section, prob- sents a maximum flooding surface. ably laid down on a deep marine, middle bathyal 4. the bellii±dubia break occurs above the change basin floor. from marly sediments to siliciclastic sediments Stratigraphic range charts of principal taxa in the that takes place in lowermost Campanian. The zonation are in Fig. 7a±c. The charts, like Fig. 6a break, as the previous one, is near a maximum and b, also show the foraminiferal zonation, estab- flooding event, i.e., the LCO of T. suspectum in lished in this study, and treated in detail below. the early middle Campanian. Taxon names followed by FO or FCO are events that 5. the dubia±szajnochae break reflects the abrupt help to define the lower level of the zones; similarly, change from siliciclastic to marly sediment at the taxon names followed by LCO or LO are events that Campanian±Maastrichtian boundary, noted in the assist with delineation of the upper level of zones. southern part of the region. Within the major units, smaller zonal subdivisions may be recognized, using a combination of subjec- 5.5.1. Protomarssonella kummi zone tive judgement from individual well study, and ob- This zone is defined on the upper range of Pro- jective subdivision from ranking and scaling analy- tomarsonella kummi, prior to the acme of Falso- 44 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 facies more Ž. ows taxa and Ž. ies zonation of the ellates Fig. 5 . The tigraphical index taxa for o King et al. op. cit. in the Ž.Ž Ž. Ž. .Ž.Ž.Ž. Ž. the region under study and taxa observed inNorth its Sea southern does part not only. compare The or zonation apply. is compared to the RASC model zonation using foraminifera and dinoflag zonation compares well with the North Sea zonation for shaly facies by King et al. 1989 , and is slightly more detailed in part. As expected, the chalk fac zones in common. Seemingly, stratigraphicNorth resolution Sea. decreases The northward, present but this study is dependents partly on a fewer, bias stratigraphically from more a patchy much wells. more limited b data set than Upper available Cretaceous t zonation, offshore mid-Norway, with stra predominant southward . The zonation compares with the North sea zonation for shaly north and for marly south facies of King et al. 1989 , with which it sh Fig. 6. a Lower Cretaceous zonation, offshore mid-Norway with stratigraphical index taxa for shaly facies more predominant northward , and for marly F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 45 Ž. Fig. 6 continued . 46 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Table 3 Summary of data properties and RASC run results for the 31 wells data set discussed in this study, using Cretaceous microfossil Summary of data properties and RASC15 results Number of namesŽ. taxa in the dictionary 589 Number of wells 31 Number of dictionary taxa in the wells 519 Number of event records in the wells 1755 Number of cycles prior to ranking 21 Number of events in the optimum sequence 72 Number of events in optimum sequence with S.D.-ave. S.D. 44 UU Number of events in the final scaled optimum sequenceŽ. including unique events shown with 81 Number of stepmodel events with more than six penalty points after scaling 14 UUU Number of normality test events shown with or 78 Number of AAAA events in scaling scattergrams 20

There are 519 dictionary taxa in the wells, 72 of which occur in seven or more wells, the threshold in the scaled optimum sequence of Fig. 5. For further discussion, see text. gaudryinella praemoesiana Ž.Fig. 7a . The following tion in well 33r9±15, is dominated by Globospiril- taxa were observed in assemblages assigned to the lina neocomiana and Patellina subcretacea.At zone: 2731.7 m, Falsogaudryinella praemoesiana is still Protomarssonella kummi LO common, but in the lower sampleŽ. 2733 m it is only common to abundant nodosariids and ostracods represented by a single specimen. Accessory species Falsogaudryinella praemoesiana FOŽ. rare include Lenticulina munsteri, ammodiscids, and no- Patellina subcretacea dosariids. A single occurrence of a species of Pro- Trocholina infracretacea tomarssonella that closely resembles M. kummi is Globospirillina neocomiana present at 2733 m. Spirillina spp. This type of assemblage has not been observed in Lagena hauteriÕiana the studied wells, offshore mid-Norway, where the Lenticulina aff. subalata lower part of the Lower Cretaceous intervalŽ be- Lenticulina cf. busnardoi LO tween the Upper Jurassic Spekk Formation and the Lenticulina munsteri Ž.common upper Hauterivian±Barremian Lyr Formation. is rep- Lenticulina heiermanni resented by a hiatus. Epistomina tenuicostata Correlation: The assemblage probably corre- Age: Hauterivian, probably early to mid Hauteriv- sponds to the Marssonella kummi Ž.sFCN 3 zone ian. of King et al.Ž. 1989 in the Viking Graben. The Environment: Neritic, carbonate substrate; higher species M. kummi has been subsequently transferred numbers of attached forms such as Patellina subcre- to the genus Protomarssonella Banner and Desai tacea Cushman and Alexander, Trocholina infra- Ž.1988 . This zone can be difficult to recognise, be- granulata Noth, Globospirillina neocomiana ŽMoul- cause the nominate species is often rare of absent. lade. , and Spirillina spp., indicate shallow neritic According to King et al.Ž. op. cit. , either the LO of conditions. P. kummi, or the FO of Falsogaudryina praemoe- Remarks: This assemblage displays high species siana can be used to identify the top of the zone. diversity and high numbers of specimens. Preserva- The Trocholina infragranulata Ž.sFCN 2 zone tion is good, colour is reddish. of King et al.Ž. op. cit. was not recognised in this Occurrence: Found in the 33r9±15 wellŽ. Fig. 8 study, because its occurrence is facies-related, and between 2731.7 and 2733 m, and observed in numer- clearly diachronous. King et al. regarded it as ous other wells in the Viking Graben. The fora- Valanginian, corresponding to the `basal Valhall miniferal assemblage at the base of the studied sec- limestone' facies of the Viking Graben. However, F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 47 hronology in a±c follows zonation established in this l zonation established in this Ž.Ž. Ž. Ž. Fig. 7. a Stratigraphic ranges of Lower Cretaceous index taxa, offshore mid-Norway, with the foraminiferal zonation established in this study. Geoc Gradstein et al. 1995 . b Stratigraphic ranges of Upper Cretaceous planktonic foraminifera index taxa, offshore mid-Norway, with the foraminiferal study. study. c Stratigraphic ranges of Upper Cretaceous benthic foraminifera, and miscellaneous index taxa, offshore mid-Norway, with the foraminifera 48 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 Ž. Fig. 7 continued . F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 49 Ž. Fig. 7 continued . 50 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Fig. 8. Stratigraphically important events and interpreted biostratigraphy in the studied interval in well 33r9±15. Note the meters thin interval assigned to the early late Albian planktonic foraminifer Globigerinelloides gyroidinaeformis zone, presently the northermost occurrence of this zone in the region. Slightly higher in this highly condensed core is the FCO of Hedbergella planispira, followed by the FO of H. delrioensis in the UÕigerinammina una zone, across the middle to late Albian boundary.

the species also occurs in limestones as young as RecurÕoides spp. Barremian in condensed facies deposited in shal- Glomospira spp.Ž. rare lower parts of the Viking Graben. Offshore mid Trocholina infracretacea Ž.rare Norway specimens were observed in the lower Bar- Patellina subcretacea remian. NeaguŽ. 1975 also reported it from the Bar- Globospirillina neocomiana: common to abundant remian of Romania. nodosariids, and ostracods LCO Lingulina semiornata LO 5.5.2. Falsogaudryinella praemoesiana zone Lenticulina aff. subalata This is a distinctive assemblage, defined on the Lenticulina cf. busnardoi LO concurrence of abundant Falsogaudryinella prae- Lenticulina munsteri Ž.common moesiana, abundant nodosariids and ostracods, and Lenticulina heiermanni LO rare to common Patellina and Globospirillina ŽFig. Lanticulina ouachensis wisselmanni LOŽ. rare 7a. . The zone corresponds to the base of the Lyr Citharina harpa Ž.rare Formation in the study area. The following taxa were Planularia crepidularis Ž.rare observed in the zone: Epistomina tenuicostata LOŽ. rare Falsogaudryinella praemoesiana LCOŽ. abundant Epistomina hechti Falsogaudryinella tealbyensis Ž.rare Epistomina caracolla Falsogaudryinella xenogena Ž.rare Conorboides lamplughi LO F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 51

Lagena hauteriÕiana LO et al.Ž. 1989 . King equated the top of this zone to the GaÕelinella sigmoicostata LOŽ. rare top of the Hauterivian. However, the identification of small planktonics, including Blefusciana spp. the top of this acme zone is somewhat subjective. In Ž.rare . the Viking Graben, the maximum numbers of Falso- Age: Generally late Hauterivian, though locally gaudryinella praemoesiana, on average are found persisting in the earliest Barremian. below the Monk Marl horizon, which is assigned to Environment: Neritic; locally either shallow or lower Barremian, but in some well sections, the deep neritic. acme of this species persists into the lowermost Remarks: The upper boundary of the zone is Barremian. The species Falsogaudryinella praemoe- recognised based on the LCO of Falsogaudryinella siana also occurs in the upper Hauterivian in Roma- praemoesiana Kaminski, Neagu and Platon. The niaŽ. Dambovicioara Valley . nominate species is abundant within the zoneŽ as much as 50% of the assemblage. , but it also persists in low numbers into the overlying zone. The assem- 5.5.3. Falsogaudryinella xenogena zone blage is characterised by high species diversity, but This zone is defined on the upper part of the also high dominance. It is often dominated by the ranges of Falsogaudryinella xenogena, F. praemoe- species Falsogaudryinella praemoesiana, but Re- siana, Patellina, and Globospirillina Ž.Fig. 7a . As- curÕoides andror Glomospira may also be present semblages assigned to this zone typically contain the in large numbers. The proportion of agglutinated following taxa: taxa is higher compared with the underlying zone. Falsogaudryinella praemoesiana LOŽ. rare Direct comparisons with the type specimens of Falsogaudryinella xenogena LOŽ. rare Falsogaudryinella moesiana Neagu described from RecurÕoides spp. the middle Albian of Romania revealed that the Glomospira spp.Ž. rare nominate species of this acme zone in the North Sea Textularia bettenstaedti is indeed a different species. Because it has charac- Ammobaculoides carpathicus LOŽ. rare ters that are considered to be more primitive, Kamin- Trocholina infracretacea LOŽ. rare ski et al.Ž. 1995a,b erected the new species Falso- Patellina subcretacea LO gaudryinella praemoesiana. Globospirillina neocomiana LO Occurrence: This zone is readily observed in common to abundant nodosariids and ostracods wells, offshore mid Norway. In the 33r9±15 well a GaÕelinella barremiana FO single core sample collected from 2729 m contains Lenticulina munsteri Ž.common an assemblage that is completely dominated by Fal- Lenticulina aff. subalata sogaudryinella praemoesiana and Protomarssonella Lenticulina guttata subtrochus. Additional taxa include common am- Lenticulina saxonica LO modiscids Ž Ammodiscus tenuissimus, Glomospira Saracenaria spp. charoides, G. gordialis., Lenticulina munsteri, and diverse unilocular species Globospirillina neocomiana. This level corresponds Epistomina hechti LO to the late Hauterivian F. praemoesiana acme zone Epistomina ornata LO Ž.sFCN 4 of King et al., 1989 . Rare planktonic Epistomina caracolla LO foraminifers are represented by Blefuscuiana spp. Conorotalites bartensteini LOŽ. rare Because of the sample spacing in the 33r9±15 small planktonics Ž.Ž.Blefuscuiana spp. rare . wellŽ. there is 4 m gap between samples , we cannot Age: Early Barremian. assume that there is a hiatus between the upper Environment: Neritic. Hauterivian and upper BarremianŽ. see below . Per- Remarks: The assemblage assigned to this zone haps more detailed sampling will reveal the presence is easily distinguished from the overlying non- of the lower Barremian F. xenogena zone as well. calcareous, agglutinated assemblages by the presence Correlation: This assemblage corresponds to the of diverse, red-stained lenticulinids and nodosariids. Falsogaudryinella moesiana Ž.sFCN 4 zone of King The nominate species, Falsogaudryinella xenogena 52 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 is never common, and it is found co-occurring with RecurÕoides spp.Ž. common F. praemoesiana. small specimens of Gyroidinoides aff. infracre- Occurrence: Found widespread offshore mid taceus. Norway, where it is characteristic of the reddish, Age: Barremian. calcareous sediments of the Lyr Formation. Environment: Deep neritic. Correlation: Corresponds to the Falsogaud- Remarks: The assemblage consisted of small-size, ryinella sp. X Ž.sFCN 5 zone of King et al. Ž. 1989 . reddish-stained specimens. The accessory species, The species illustrated by King et al.Ž. op. cit. was tentatively identified as Gyroidinoides aff. infracre- named Falsogaudryinella xenogena by Kaminski et taceus, differs from the typical Albian form in its al.Ž. 1995a,b , partly because the authors wished to much smaller size and in possessing fewer chambers. preserve the letter `X' in the name. The name also Occurrence: The zone is rarely observed, off- refers to the fact that is it `foreign',Ž i.e., not ob- shore mid-Norway, due to the common presence of a served in the Tethys region. . In the Viking Graben, hiatus, extending through part of the Aptian. A sin- the nominate species mostly occurs in the lower to gle core sample collected at 2725 m in well 33r9±15 middle Barremian. It generally occurs below the in the northern Viking Graben, recovered a rich Monk Marl horizon, though it is occasionally ob- foraminiferal assemblage, assigned to this zone. The served in or above it, partially overlapping in range sample consists almost entirely of red-coloured cal- with GaÕelinella barremiana, the nominate species careous benthic foraminifers, dominated by the Bar- of the overlying zone. remian index species GaÕelinella barremiana Bet- In the absence of the nominate taxon, the LO of tenstaedt. This species is the index taxon of the diverse, reddish lenticulinids can be used to recog- upper Barremian G. barremiana zone ŽsFCN 6 of nize the top of the zone. Offshore mid Norway, the King et al., 1989. . The sample also includes diverse sediments immediately overlying the zone, are non- nodosariids, and single specimens of Gyroidinoides calcareous claystones and their benthic foraminiferal and Ammodiscus. assemblages are stained green. At localities in the Correlation: GaÕelinella barremiana Betten- Viking GrabenŽ. UKCS Blocks 21 and 22 where the staedt is a cosmopolitan species, known from the Barremian section is more complete, the first down- upper middle Barremian to upper Barremian of the hole occurrence of diverse lenticulinids, and a peak northern North Sea, and from the upper Barremian to in their relative abundance correlates to a level just lower Aptian of northwest Germany, and offshore below the Monk MarlŽ. ca. 20±40 m below . Canada. This zone is equivalent to the G. barremi- Offshore mid-Norway, the lateral equivalent of ana Ž.sFCN 6 zone of King et al. Ž. 1989 . the Monk Marl horizon was not observed in the logs, possibly owing to the presence of a hiatus. This horizon represents a regional dysaerobic facies in the 5.5.5. Verneuilinoides chapmani zone North Sea, and contains a distinctive, white-stained This zone is defined on the upper part of the benthic foraminiferal assemblage, with common ranges of Verneuilinoides chapmani, and Cau- Glomospira. The species Glomospira gaultina is dammina crassa Ž.Fig. 7a . Assemblages assigned to well represented in the Monk Marl. The significance this zone consist mostly of green-stained, deep-water of Lower Cretaceous Glomospira assemblages has agglutinated foraminifers. However, in some wells, been discussed by Kaminski et al.Ž. 1992 . some calcareous species may also be present with few specimens, especially at the base of the zone. 5.5.4. GaÕelinella barremiana zone The following taxa have been observed in assem- This zone is defined on the upper part of the blages assigned to the zone: range of GaÕelinella barremiana Ž.Fig. 7a . Assem- Verneuilinoides chapmani LO blages assigned to this zone typically contain the Caudammina crassa following taxa: RecurÕoides spp.Ž. common GaÕelinella barremiana LO Glomospira sp.Ž. common Glomospira spp.Ž. common Cribrostomoides nonioninoides LCOŽ. frequent F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 53

Kalamopsis grzybowskii Ž.rare Glomospira charoides Ž.abundant Glomospira gaultina Ž.rare Glomospira gordialis Bathysiphon sp.Ž. rare Ammodiscus spp. Rhabdammina, Rhizammina Ž.few . UÕigerinammina una n. sp.Ž. rare Age: Late Aptian±early Albian. Cribrostomoides nonioninoides Ž.rare Environment: Outer neritic±upper bathyal. Textularia spp.Ž. rare Remarks: The taxonomic diversity is relatively PseudoboliÕina Õariabilis high, and some deep-water taxa are present, includ- Gyroidinoides infracretaceus ing Kalamopsis grzybowskii, Bathysiphon sp., and GaÕelinella intermedia. Caudammina crassa. The relative proportion of Glo- Age: Middle Albian. mospira gordialis is higher in the lower part of the Environment: Upper bathyal. zone. Increased numbers of tubular agglutinated Remarks: The assemblage is strongly dominated forms such as Rhabdammina, Rhizammina, and by RecurÕoides spp., and Glomospira spp. The other Bathysiphon are interpreted as indicating deposition agglutinated species listed above occur as single in deeper water. Dinoflagellate events present in this specimens. The calcareous benthic and planktonic zone include the LO of Lithodinia stoÕeri ŽFig. 5, forms are rare, and may be caved. right. . Occurrence: The zone is missing in many wells Occurrence: Observed widespread, offshore mid due to a widespread hiatus of Aptian through early Norway. middle Albian age; it occurs condensed in well Correlation: This zone is equivalent to the 6406r2±2. Verneuilinoides chapmani Ž.sFCN 8 zone of King Correlation: This zone corresponds to the Recur- et al.Ž. 1989 . In the lower part of the zone, the ratio Õoides sp. Ž.sFCN 10a zone of King et al. Ž. 1989 . of Glomospira gordialis to Glomospira charoides The species Globigerinelliodes gyroidinaeformis, increases considerably. This feature is often observed the nominate taxon of the King's underlying zone in the lower Albian of the Viking Graben, and FCN 9 has not been observed, offshore mid-Norway. probably denotes a more dysoxic environment. In the It is, however, known from the northern Viking lowermost part of the zone, a few pyritized speci- Graben in well 33r9±15Ž. Fig. 8 at 2723 m, dated mens of Lenticulina, and other calcareous benthics latest early Albian. The core sample collected at are occasionally observed. This is consistent with the 2723 m in that well contains an assemblage observation by King et al.Ž. 1989 , that calcareous comprised mainly of calcareous benthic species and benthic foraminifers sometimes ``re-appear downsec- Hedbergella. The dominantŽ. and most distinctive tion in the lowest part of the wxV. chapmani zone''. taxon is Globigerinelloides gyroidinaeformis King et al.Ž. op. cit. correlated the lowest part of Moullade, a species that is probably a benthic zone FCN 8 with the uppermost Aptian. In all the form because of its slightly streptospiral coiling, wells studied, the base of this zone lies discon- unusual for planktonics. Moreover, it is often found formably upon the BarremianŽ mostly lower Bar- in assemblages where other well-known planktonic remian. Lyr Formation. Therefore, a regional hiatus forms are absent. This distinctive species is often that encompassed most of the Barremian and Aptian observed as a `flood', and defines the latest early is present in the area. The hiatus corresponds to a Albian Globigerinelloides gyroidinaeformis Ž.FCN 9 change in lithology from reddish marls and lime- zone in the Viking GrabenŽ. King et al., 1989 . The stones below, to greenish non-calcareous claystones species is also known from the Grand Banks, off- above. shore eastern Canada, and from the Vocontian Basin, France. This stratigraphic level has not yet been 5.5.6. RecurÕoidesrGlomospira zone found further north in the region; either the species is This assemblage zone contains the following ecologically excluded from the areaŽ which is un- characteristic species: likely, as it is common in the Viking Graben. or RecurÕoides spp.Ž. acme more likely, a hiatus is present in the offshore mid- PlectorecurÕoides irregularis Norway area. 54 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

5.5.7. UÕigerinammina una zone LO of Textularia bettenstaedti have been observed This zone is defined on the upper part of the in this zone. Both events are reported to occur within range of UÕigerinammina una, together with Am- the early Albian R. minuta zoneŽ. zone FCS 8 , of moanita globorotaliaeformis Ž.Figs. 5 and 7a . As- King et al. in the southern North Sea. UÕigerinam- semblage assigned to this zone generally consist of mina una n. sp. is formally described as a new taxon diverse, green-stained deep-water agglutinated in Appendix B. foraminifers, with few calcareous benthics present, According to our observations, Ammoanita and common to frequent planktonics, belonging to ()Trochammina globorotaliaeformis n. sp. has a few species. The following taxa have been observed tighter coil than the Paleocene A. ingerlisae Grad- in the zone: stein and Kaminski and, on average moreŽ. not fewer UÕigerinammina una n. sp. LOŽ. common chambers in the last whorl. In local well completion Falsogaudryinella alta reports such specimens are referred to as Trocham- Textularia bettenstaedti Ž.rare ina globorotaliaformis, and constitute a useful mid- Haplophragmoides spp. upper Albian index species. This A. globorotaliae- Reophax troyeri LO formis n. sp. is formally described as a new taxon in Ammoanita globorotaliaeformis n. sp. LO Appendix B. Cribrostomoides nonioninoides LO Dinoflagellate events present in his zone include Trochammina abrupta Ž.Fig. 5 Apteodinium grande LCO, and Lithos- Gyroidinoides infracretaceus phaeridium arundum LO; OÕoidinium scabrosum GaÕelinella intermedia and Endoceratium turneri range through this zone Pleurostomella barrowsi LO upwards. In the zone, as far as observed in several Glomospira charoides wells, the number of planktonic foraminifers in- Glomospira gordialis creases stratigraphically upwards, reflecting a change Hedbergella planispira FCO from more restricted marineŽ. dysaerobic to more Hedbergella infracretacea Ž.common oxygenated, open marine conditions. A similar Hedbergella delrioensis Ž.rare change was reported by King et al.Ž. 1989 from the Globigerinelloides bentonensis Ž.rare . northern North Sea, as reflected in a change from Age: Late middle to early late Albian. non-calcareous to calcareous claystoneŽ top of Sola Environment: Upper bathyal. Formation. . This environmental change is further Remarks: Assemblages assigned to this zone, discussed in Chapter 7 on Paleobathymetry. typically are comprised of agglutinated, and few Occurrence: Found in a majority of the wells calcareous benthic taxa, and often common to fre- studied, offshore mid-Norway. quent planktonics, mostly Hedbergella planispira. Correlation: This zone corresponds to the Falso- The nominate taxon, UÕigerinammina una n. sp. gaudryinella sp. 1Ž. FCN 10b zone of King et al. apparently is a boreal species restricted to the Nor- Ž.1989 . In the Kirchrode-1 Borehole in the Lower wegian Sea and North Sea region. It appears not to Saxony Basin, the change from dominant Hed- possess calcareous cement, therefore it cannot be bergella planispira Ž.below to Hedbergella delrioen- assigned to the genus Falsogaudryinella. Most likely sis Ž.above is observed within the early late Albian it belongs in the genus UÕigerinammina, as origi- P. columnata calcareous nannofossil zone, and the nally reported by Burnhill and RamsayŽ. 1981 ; more Ticinella raynaudi planktonic foraminiferal zone details are in Appendix B. It has not been found in Ž.Weiss, 1997 . The zone probably correlates to the the Albian of the Kirchrode-1 BoreholeŽ Jaroslaw inflatum ammonite zone. Tyszka, personal communication. , or in deep-sea deposits. The acme of UÕigerinammina una n. sp. itself often forms a narrow zone, but it is also found 5.5.8. Osangularia schloenbachi zone in low numbers in both the overlying and underlying This zone is defined on the upper part of the zones. Additionally, the LO of Pseudonodosinella stratigraphic range of Osangularia schloenbachi. troyeri Ž.sReophax minuta of other authors and the Sigmoilina antiqua, Falsogaudryinella alta, and Glo- F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 55 bigerinelloides bentonensis may co-occur.Ž Figs. 5 recognition of the zone may be hampered by cavings and 7a. . Assemblages assigned to this zone typically from overlying, fossiliferous strata assigned to lower contain the following taxa: Cenomanian. An uppermost Albian hiatus in some of Osangularia schloenbachi LOŽ. rare to common the wells may truncate part of all of this zone, GaÕelinella intermedia possibly related to the pronounced eustatic offlap Gyroidinoides infracretaceus cited by Hardenbol et al.Ž. 1993 , and by Rohl and Sigmoilina antiqua OggŽ. 1996 at the base of the inflatum zone. The Lenticulina muensteri hiatus is visualized by the large interfossil distance Epistomina spinulifera LO below A. grande, at the base of the RASC interval ValÕulineria gracillima Ž.rare zone in Fig. 5Ž. left . Falsogaudryinella alta LOŽ. rare Correlation: This zone corresponds to the Osan- ClaÕulina gaultina gularia schloenbachi Ž.sFCN 12a zone of King et Glomospira charoides Ž.often common al.Ž.Ž 1989 see also Crittenden, 1983, 1987 . . King et Ammodiscus tenuissimus al.Ž. 1989 reported that the stratigraphical range of Hedbergella infracretacea LOŽ. common this species is diachronous from south to north, Hedbergella delrioensis FCO occurring in the mid-Albian in the southern sector of Hedbergella planispira Ž.rare the North Sea, but persisting to the upper Albian in Globigerinelloides bentonensis FO the Viking Graben. The underlying Globigerinel- pink coloured Inoceramus prisms. loides bentonensis Ž.sFCN 11 zone of King et al. Age: Late Albian. Ž.1989 is not recognised in the study area owing to Environment: Upper bathyal. the rarity of this speciesŽ. Fig. 10b . In the Kirchrode-1 Remarks: This is a diverse assemblage, com- Borehole in the Lower Saxony Basin, NW Germany, prised of calcareous and agglutinated taxa, stained the level with abundant Globigerinelloides bentonen- green. The species Osangularia schloenbachi occurs sis correlates to the late Albian E. turriseiffelii cal- as an acme, and rare specimens are found in the careous nannofossil zoneŽ. Weiss, 1997 . The zone underlying zone. The species is known from the probably correlates to the dispar ammonite zone upper Albian of Romania, Poland, Germany and Ž.Fig. 11 . France, and is probably of Tethyan origin. In addition to the nominate taxon, GaÕelinella intermedia, 5.5.9. Sigmoilina antiqua zone Gyroidinoides infracretaceus, and lenticulinids are This zone is defined on the upper part of the also common, as well as Glomospira charoides. stratigraphic range of Sigmoilina antiqua Ž.Fig. 7b ; Planktonic foraminifers are often abundant, and are Textularia sp. 1 Burnhill and Ramsay, Pseudotextu- strongly dominated by small specimens of H. delri- laria cretosa, RecurÕoides imperfectus, and Plec- oensis, probably the stratigraphic onsetŽ. FCO of a torecurÕoides alternans also occur in this zoneŽ Figs. regional bloom that ends in the Hedbergella delri- 5 and 7a,b. . Assemblages assigned to this zone oensis LCO zone, as discussed belowŽ. Fig. 11 . typically contain the following taxa: Dinoflagellate taxa present in the zone include Sigmoilina antiqua LO Lithosphaeridium conispinum LO, OÕoidinium Pseudotextulariella cretosa LO scabrosum LO and Apteodinium grande LO, marker Spiroplectinata annectens LO taxa for upper AlbianŽ Costa and Davey, 1992; E. Arenobulimina adÕena Monteil, pers. comm., 1997. . Marssonella ozawai In the RASC scaled optimum sequence of Fig. 5 Textularia sp. 1 Burnhill and RamsayŽ. 1981 LO Ž.left this zone is represented by a tight cluster of Textularia chapmani five events, and in the corresponding optimum se- Textularia foeda quence of Fig. 5Ž. right by taxa at rank positions PlectorecurÕoides alternans LO 85±90. RecurÕoides imperfectus LO Occurrence: Found in several of the wells, off- Hippocrepina depressa shore mid-Norway. Where O. schloenbachi is rare, ValÕulineria gracillima 56 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Hedbergella delrioensis FCO including missing data, in the wells that penetrate Hedbergella planispira this stratigraphic level. The zone may be identified in GaÕelinella sp. XŽ. unpublished LO well 6507r2±3 near 3350 m, and in well 35r3±4 GaÕelinella intermedia near 3370 m. LingulogaÕelinella jarzeÕae Correlation: This zone corresponds to the Sig- pink coloured Inoceramus prisms. moilina antiqua Ž.sFCN 12b zone of King et al. Age: Early Cenomanian. Ž.1989 , and to the upper part of the deep marine Environment: Upper bathyal. assemblage zone with PlectorecurÕoides alternans Remarks: Sigmoilina antiqua, the nominate taxon Ž.Geroch and Nowak, 1984 . The zone probably cor- is rare. Its stratigraphic range extends from the two relates to the lower part of the mantellircantianum underlying zones, UÕigerinammina una n. sp. zone, ammonite zoneŽ. Fig. 11 . and O. schloenbachi zone, into this zone. Average LO events that co-occur in this zone are Pseudotex- 5.5.10. Hedbergella delrioensis LCO zone tulariella cretosa, Marsonella ozawai, Arenobulim- This distinctive zone is defined on the LCO of ina adÕena, and other taxa listed above. GaÕelinella Hedbergella delrioensis; it may occur in floods, sp. X, with its steep last chamber is probably a new accompanied by the LCO of H. planispira ŽFigs. 5 form, and together with Textularia sp. 1 may be and 7b. . The following taxa have been observed in restricted to the northern North Sea and Norwegian assemblages assigned to this zone: Sea. When and where found with sufficient number Hedbergella delrioensis LCOŽ common to abun- of specimens, in offshore Norway wells, both taxa dant; Plate I. should be formally described as new taxa. The plank- Hedbergella planispira LCOŽ common to fre- tonic foraminifers Hedbergella delrioensis and H. quent; Plate II. planispira locally are common in this zone; Glo- Hedbergella sigali Ž.rare bigerinelloides bentonensis occurs as isolated speci- Whiteinella brittonensis FOŽ isolated occurrence, mens, and is only common in the immediately under- rare. lying zone. Praeglobotruncana praehelÕetica FOŽ isolated oc- The dinoflagellates OÕoidinium Õerrucosum and currence, rare. Endoceratium turneri on average top in this zone, GaÕelinella intermedia Ž.rare and in fact form the constituent zonal cluster in the GaÕelinella cenomanica Ž.rare scaled optimum sequenceŽ. Fig. 5, left , which corre- ValÕulineria gracillima Ž.rare lates to the optimum sequenceŽ. Fig. 5, right at rank LingulogaÕelinella jarzeÕae LOŽ. rare positions 80 to 84. Arenobulimina spp.Ž. rare According to King et al.Ž. 1989 , the LO events of Glomospirella gaultina foraminifers in this zone are indicative of lower RecurÕoides imperfectus LO Cenomanian strata, in agreement with the upper part Hippocrepina depressa LO of the stratigraphic range of the dinoflagellate taxon PlectorecurÕoides spp. LO OÕoidinium Õerrucosum Žsee Costa and Davey, Textularia sp. 1 LOŽ. rare 1992. . Textularia foeda Ž.rare . Occurrence: Widespread offshore mid-Norway. Age: Late early Cenomanian, probably extending In wells where the lithology is sandyŽ with gravity into early middle Cenomanian. flows assigned to the Lange Formation. , this zone Environment: Upper bathyal. may be difficult to detect. The lack of clustering of Remarks: In many wells, including 35r3±5 be- events assigned to this zone in the scaled optimum tween 3035 and 2930 m, 6507r2±3 between 3300 sequenceŽ. Fig. 5, left , indicates considerable `noise', and 3200 m, and 6507r6±2 near 2950 m, a distinc-

Plate I. Figs. 1±12. Hedbergella delrioensis Ž.Carsey . Well 35r3±4, Osangularia schloenbachi zone through Hedbergella delrioensis LCO zone, 3224±3411 m. F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 57 58 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 59 tive assemblage is observed with Hedbergella delri- ing to ProkophŽ.Ž. 1997 Fig. 11 , the upper part of the oensis LCOŽ last common and last consistent occur- LCO of H. planispira and H. delrioensis in NW rence, as observed uphole. , in association with GaÕe- Germany corresponds to the dixoni ammonite zone linella intermedia, G. cenomanica, ValÕulinera of late early Cenomanian age. We adhere to this gracillima, LingulogaÕelinella jarzeÕae, Plectore- correlation for offshore Norway curÕoides alternans, RecurÕoides imperfectus, Hip- From the age of the underlying and immediately pocrepina depressa, Glomospirella gaultina, Ammo- overlying zones, and the evidence cited above, we sphaeroidina sp. 1Ž. RRI , Eggerellina mariei, Textu- assign the Hedbergella delrioensis LCO zone to the laria foeda, and Tritaxia pyramidata. The majority upper part of the lower Cenomanian, possibly ex- of benthic taxa assigned to this zone are rare. Among tending into middle CenomanianŽ. see below . planktonics Hedbergella planispira LCO occurs Occurrence: Widespread and distinctive, off- slightly down in this zone; H. sigali, Whiteinella shore mid-Norway. brittonensis and Praeglobotruncana praehelÕetica, Correlation: The zone overlaps with the lower occur at few localities only in this zone, and are rare; part of the northern North Sea zone of H. brittonen- in two wellsŽ. 35r3±5 and 36r1±2 single speci- sis Ž.sFCN 13 of King et al. Ž. 1989 containing mens of Rotalipora cf. greenhornensis were re- abundant hedbergellids, assigned broadly to the mid- ported. dle part of Cenomanian. Offshore mid-Norway, the Among dinoflagellates occurŽ. average LO Rhom- top of the zone extends above the sands of the Lange bodella paucispina, Fromea sp. 2, Epelidos- Formation, and is below or in sand of the basal phaeridia spinosa, Xiphophoridium alatum and Lysing Formation. Since recognition of the zone Litosphaeridium siphoniphorum. The latter two taxa is dependent on suitable, shaly lithologyŽ the may extend in the overlying zone. The firstŽ. up well widespread gravity flow sands are not fossiliferous. , occurrence of Heterosphaeridium difficile is in this the full stratigraphic extent of the zone remains to be zoneŽ. e.g., in well 6507r7±1 at 3506 m , as reported determined. It probably incorporates a flooding hori- by Bell and SelnesŽ. 1997 . These authors regard this zon in the upper part of the lower Cenomanian, event to be close to the boundary of lower and truncated by the mid-Cenomanian non-sequenceŽ like middle Cenomanian, in good agreement with strati- the Rouen hardground of northern France. , as will be graphic evidence cited below. discussed in Section 7.4. The dinoflagellate assemblage with E. spinosa, R. paucispina, X. alatum and L. siphoniphorum overlap 5.5.11. Whiteinella brittonensis zone ranges in lower Cenomanian strataŽ Costa and Davey, This zone is defined on the lower part of the 1992. , and the benthic foraminifer L. jarÕzeÕae in range of Whiteinella brittonensis, with rare Hed- the southern North Sea ranges upwards into the bergella spp., and Praeglobotrunacana spp.Ž Figs. 5 lower CenomanianŽ. King et al., 1989 . The possible and 7b. . Also present may be GaÕelinella interme- presence in this zone of the planktonic foraminifer dia, ValÕulineria gracillima, and Glomospirella Rotalipora greenhornensis would indicate an early gaultina. Dicarinella and Marginotruncana taxa are to middle Cenomanian age. RecurÕoides imperfectus not present in this zonal interval. The following taxa and PlectorecurÕoides irregularis commonly occur have been observed in assemblages assigned to this in the lower zones described above, and occasionally zone: range upwards into this zone, together with Hip- Hedbergella delrioensis Ž.rare pocrepina depressa. The upper range of these taxa Hedbergella planispira Ž.rare Geroch and NowakŽ. 1984 assigned to the Plectore- ClaÕihedbergella simplex LOŽ. rare curÕoides alternans zone,which in the Carpathians Whiteinella brittonensis FO extends into the lower part of Cenomanian. Accord- GaÕelinella cenomanica LOŽ. rare

Plate II. Figs. 1±12. Hedbergella planispira Ž.Tappan . Well 35r3±5, Osangularia schloenbachi zone through Hedbergella delrioensis LCO zone, 2930±3291 m. 60 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

GaÕelinella intermedia LOŽ. rare Occurrence: The zone is widespread, offshore LingulogaÕelinella spp. Norway, but not easy to recognized, due to sandy ValÕulineria gracillima LOŽ. rare facies. Bulbobaculites problematicus Correlation: The W. brittonensis zone corre- Glomospirella gaultina LCO sponds to the zone of the same name for the shale UÕigerinammina() pre- jankoi facies of the northern North SeaŽ. King et al., 1989 . Ammosphaeroidina sp. It is possible that the upper part of the zone includes Eggerellina mariei LO. part of the unfossiliferous beds that occur as a result Age: Late middle to early late Cenomanian. of widespread dysaerobia, or anoxia near the Ceno- Environment: Upper bathyal. manianrTuronian boundaryŽ. see below . Remarks: The interval from the level of Batiola- dinium jaegeri LO upwards to Heterosphaeridium 5.5.12. Dicarinella zone difficile LCO, between optimum sequence positions This zone is defined on the presence of Di- 68 and 47, groups relatively tightlyŽ. Fig. 5 . This carinella hagni-indica, D. imbricata,orD. primitiÕa tight clustering in the scaled optimum sequence is Ž.Figs. 5 and 7b . Other key taxa that may be present the result of frequent cross-overs of the events in the include Whiteinella inornata, W. paradubia, Prae- wells. globotrunaca stephani LO, and Hedbergella hoelzi A tight, lower subgroup in this interval, corre- LO. The following taxa have been observed in as- sponding to rank positions 68 to 64 in the optimum semblages assigned to this zone: sequence, is assigned to the W. brittonensis zone, Dicarinella hagni indica LO with the events listed above, some of which are Dicarinella imbricata LO scarce, or absent in the northern part of the region Dicarinella primitiÕa LO under study. The depth interval in wells that might Gaudryina filiformis be expected to contain this zone is often impover- Hedbergella delrioensis LOŽ. isolated specimens ished in fossils due to poor sample recovery from H. planispira LOŽ. isolated specimens turbine drilling, widespread watermass dysaerobia, Hedbergella hoelzi LO stratigraphic hiatusess, or gravity flow sands. This Praeglobotruncana stephani LO zone, and the immediately overlying one may be Whiteinella brittonensis LO difficult or impossible to separate. Whiteinella inornata As far as may be determined, this zone contains Whiteinella paradubia rare Hedbergella delrioensis, H. planispira, UÕigeri- Marginotruncana marginata FO nammina() pre- jankoi, Glomospirella gaultina, Heterohelix globulosa Ž.rare GaÕelinella intermedia, G. cenomanica, Ammo- Bulbobaculites problematicus LO sphaeroidina sp., Eggerellina mariei, and White- Stensioeina humilis LOŽ. rare inella brittonensis. Occasional events are ClaÕihed- LingulogaÕelinella spp.Ž. rare bergella simplex, and a specimen of Rotalipora cf. GaÕelinella balthica Ž.rare greenhornensis in southern well 36r1±2 at 2660 m. Rzehakina spp. FOŽ. including R. minima The age assigned to the zone is late middle to early Caudammina oÕuloides late Cenomanian, but more study of this interval is UÕigerinammina jankoi Ž.rare desirable. Psammosphaera spp.Ž. frequent Among dinoflagellates occur Batioladinium Allomorphina pyriformis LO jaegeri LO, Endoceratium dettmaniae LO, E. lud- Allomorphina halli LO brookii LO Dorocysta litotes, and Lithosphaeridium CrT boundary gamma spikeŽ more than one spike siphoniphorum LOŽ. southern wells only . These may be present. events together are assigned a late middle to early pyritized small diatomsŽ. frequent late Cenomanian ageŽ. Costa and Davey, 1992 , in pyritized spumellarian radiolariansŽ. rare . agreement with the age assigned to the W. brittonen- Age: Latest Cenomanian±middle Turonian. sis zone. Environment: Upper bathyal. F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 61

Remarks: For the reasons, mentioned also with maybe more or less associated with this `Bonarelli' the immediately underlying zone, this zone maybe type intervalŽ. G. Bell, pers. comm., 1996 , although difficult to separate from the underlying one. Where RASC does not link the two events closely on siliciclastic sedimentation rates are high, with pre- averageŽ. Fig. 5 . A reason for the latter may be high dominant gravity-flow sands, a typical Psam- variance in the average stratigraphic position of both mophaerarsmall pyritized diatom biofacies occurs, events. sprinkled with isolated H. delrioensis, H. planispira Considerable confusion exists over the identity of or Dicarinella. In few wells, particularly in the south triserial to twisted biserial agglutinated benthic where sand are less common, planktonic foraminifers foraminifer specimens commonly found in the mid- are more diverse than in the immediately underlying dle to upper Cretaceous of wells. CavedŽ. ? K. or overlying zones, and include Praeglobotruncana conÕersa may be mislabelled as Gaudryina fili- stephani, P. delrioensis, Dicarinella hagni indica, formis, and be difficult to distinguish from it. A Dicarinella imbricata, Marginotruncana marginata detailed taxonomic study of such morphotypes in the FO, Dicarinella primitiÕa, Hedbergella hoelzi, H. wells is warranted. delrioensis Ž.rare , Whiteinella archeocretacea, W. In core sample 2885.5 m in well 6507r2±3, inornata, W.paradubia,andW. brittonensis. assigned to this zone, Rzehakina minima has its first Marginotruncana is mostly rare and only represented stratigraphic occurrence. Such would agree with the by M. marginata. From the overlap of planktonic report by Kaiho and HasegawaŽ. 1994 that in Japan foraminiferal ranges, the zone may be assigned a late RzehakinaŽ. R. epigona appears in Turonian strata. Cenomanian through early middle Turonian age Bulbobaculites problematicus commonly occurs in Ž.Stainforth, 1981; Robaszynski et al., 1984 . this zone, and rarely in the immediately underlying Marginotruncana marginata and Dicarinella are re- one, which agrees with broad age assignment for this stricted to post Cenomanian strata, and assists with taxon inŽ. Kuhnt and Kaminski, 1990 . constraining the age of the upper part of the zone. Among dinoflagelle cyst events Maghrebinia It is likely that rare last occurrences in this zone membraniphorum LO, Palaeohystrichosphera infu- of UÕigerinammina jankoi are in situ, since this sorioides acme and LCO, Heterosphaeridium diffi- taxon is known from the Turonian through Santonian cile FCO, Stephodinium coronatum LO, and Ž.Geroch and Nowak, 1984 . Spiniferites porosus occur, associated with Turonian The assignment of an event labelled Cenoma- strata according to Costa and DaveyŽ. 1992 . Doro- nianrTuronianŽ. CrT boundary gamma spike Ž Fig. cysta litotes LO also may be present, but was omit- 5. , reflects our hypothesis that a distinct and narrow ted from RASC input data due to erratic stratigraphic Ž.less than a few meters thick gamma ray high on occurrence. physical well logs, near the base of this zone, corre- The age of the Dicarinella zone is Turonian in its sponds to the well-known, global oceanic, `anoxic', upper part, while the lower part may extend down- Event-2Ž. Bonarelli , reported widely in latest Ceno- ward into Cenomanian, hence the zone is bracketed manian through early Turonian strata. The exact to occur across the CrT boundary. High sedimenta- reason for the spike in the wells is unclear, but it is tion rates, a sandy, dysaerobic facies with occasion- assumed to be high thorium or uranium concentra- ally much pyrite, and turbo drilling in many wells tion, associated with organic rich levels. We have no prevent satisfactory stratigraphic resolution across reason to believe that the spike is a local feature; in this interval. few wells more than one spike occurs over a short Occurrence: This zone is widespread and rela- interval in this zone. From cuttings it cannot be tively thick, offshore Norway. ascertained that the spike is actually associated with Correlation: The Dicarinella zone corresponds an interval barren of microfossils, but in cores in to the zone of the same name in the northern North well 6507r2±3 a distinct reduction to virtually no Sea, characterised by an downhole influx of abun- microfossils at and below the CrT boundary gamma dant planktonic foraminifers, dominantly hedbergel- spike at 2972 m is observed. A peculiar, monotypic lids and Dicarinella spp.Ž. King et al., 1989 . Off- NyktericystarAustralosphaera dinocyst assemblage shore Norway, this simple definition of King et al., 62 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 op. cit.. may apply to some southern wells. The stratigraphic facies change; in the optimum sequence lower part of the zone contains strata coeval to the of Fig. 5Ž. right the zone is recognized at rank organic- rich Plenus marls, and the Blodoks shales of positions 47±50. the North Sea and England. TheŽ. local relative abundance of Marginotrun- cana, together with H. difficile probably is the result 5.5.13. Marginotruncana zone of a condensed sedimentary sequence under open This zone is defined on the presence of marine and relatively warm water condition. Unfor- Marginotruncana marginata, M. coronata, Globo- tunately, the dinoflagellate cyst Heterosphaeridium truncana linneiana gr., and G. fornicata Žprimitive difficile may display more than one LCO or acme, morphotype.Ž Figs. 5 and 7b . . The following taxa hence this event may not be unique. The acme have been observed in assemblages assigned to this occurrence of H. difficile, according to Costa and zone: DaveyŽ. 1992 suggests a Turonian age, with the Margintruncana marginata taxon ranging into the Coniacian. Among dinoflagel- Marginotruncana fornicata Žprimitive morpho- late cyst that range through the upper part of the type. zone, and may extend slightly in the overlying Marginotruncana coronata foraminiferal S. granulata polonica zone, are Globotruncana linneiana gr. Chatangiella sp. 1 Stratlab, Trithyrodinium reticula- Dicarinella concaÕata Ž.isolated specimens tum, Surculosphaeridium longifurcatum and Het- Dicarinella carinata Ž.isolated specimens erosphaeridium difficile. Whiteinella archeocretacea Occurrence: This zone is clearly recognized in Conorbina supracretacea southern well 35r3±4 from 2425 to 2460 m. Where LingulogaÕelinella sp. globotruncaniid foraminifers are missing, as in many Nuttalina florealis northern wells, recognition of the zone may be diffi- Globorotalites spp. cult. Gaudryina filiformis Correlation: A M. marginata zone is defined by UÕigerina jankoi King et al.Ž. 1989 for the northern North Sea, and Haplophragmoides aff. walteri Žsensu Kuhnt and was assigned a late Turonian through early Conia- Kaminski, 1990. cian age. These authors extend the overlying S. Inoceramus needles. granulata polonica interval zone beyond the Santo- Age: Late Turonian±Coniacian. nian range of the nominate taxon down into the Environment: Upper bathyal. upper Coniacian. We restrict the S. granulata Remarks: This zone is recognized in few wells in polonica zone to the Santonian. the southern part of the study region, where it constitutes a downhole influx of Marginotruncana, 5.5.14. Stensioeina polonica zone Globotruncana and Whiteinella. An distinct influx of This distinctive zone is defined on Stensioeina Marginotruncana, together with Whiteinella was for Ž.granulata polonica LO Ž Figs. 5 and 7c . . The fol- example observed in the 35r3±4 well, together with lowing taxa have been observed in assemblages as- isolated specimens of Dicarinella concaÕata and D. signed to this zone: carinata. The overlap of ranges of the latter two taxa Stensioeina() granulata polonica LO is indicative of Coniacian strataŽ Robaszynski et al., Globorotalites multiseptus 1984. . Nuttalina florealis The zone constitutes the upper part of the high GaÕelinella beccariiformis FO sedimentation rate interval and sandy facies of the Epistomina supracretacea Lysing Formation in northern wells, where Gyroidinoides beisseli globotruncaniid planktonic foraminifers are mostly Globotruncana marginata Ž.rare absent; hence recognition of the zone there may be Globotruncana linneiana group Ž.rare difficult. The large interfossil zone limit in Fig. 5 Globotruncana fornicata Ž.rare Ž.left at H. difficile LCO reflects this important Heterohelix sp. F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 63

Inoceramus needlesŽ. common foraminifers, and locally radiolarians. In a few wells, Archeoglobigerina spp. such as 35r3±4 this zone merges with the immedi- Allomorphina sp. ately underlying S. granulata polonica zone, but on Tritaxia spp. average the two events are clearly superpositional Age: Early to middle Santonian. Ž.Fig. 5 , possess low variances Ž. Fig. 9 , and are Environment: Upper bathyal. assigned to successive and separate zones. Spherical Remarks: The nominate zone marker is the key and lenticular radiolarians may be common in this taxon in this easily recognizable zone, with the last zone, but are more so in the overlying Fenestrella stratigraphic occurrence of the nominate species de- bellii zone. In the southern part of the study areaŽ 34 limiting its upper boundary. The zonal interval also and 35 blocks. , the lower stratigraphic ranges of contains various other calcareous taxa, listed above. Tritaxia dubia, Globotruncana bulloides and Planktonic foraminifers decrease stratigraphically Whiteinella baltica are in this zone, and Ar- upwards in this zone, and are much more typical for chaeoglobigerina may also be present. the immediately underlying zone. Deep marine ag- The sudden disappearance of common Inocera- glutinated benthics mostly are scarce, but less so mus needles, stratigraphically upwards suggests a offshore mid-Norway. UÕigerinammina jankoi only regional hiatus, tentatively shown in Fig. 2 to span was observed in few southern wells. Lenticular radi- part of upper Santonian and lowermost Campanian. olarians also occur. In some wells the immediately Age: Late Santonian. overlying Inoceramus LCO zone and this zone are Environment: Bathyal. mergedŽ. see below . Occurrence: The Inoceramus LCO zone is Occurrence: This zone occurs widespread, off- widespread, offshore Norway, and easily recogniz- shore Norway, and in some wells were the Inocera- able. mus LCO zone merges with this zone, constitutes the Correlation: This zone correlates to part or all of first downhole carbonate rich interval, below the the `radiolaria' zone in the North SeaŽ King et al., thick siliciclast interval assigned a Campanian age. 1989. that, according to these authors may have a Correlation: This zone correlates to the Sten- somewhat spotty distribution northward. The latter sioeina granulata polonica zone of KochŽ. 1977 , of might be the result of local dissolution of silica. The early and early middle Santonian age in NW Ger- distribution of the Inoceramus zone north of the many. This is the only Stensioeina taxon from the North Sea reflects a temporal increase of carbonate evolutionary plexus of Stensioeina that is widespread, productivity during a time of limited terrigenous offshore Norway, and also is observed in the Voer- sedimentation. ing Basin. Elsewhere in NW Europe six or more successive Stensioeina zones are recognized from Turonian to Campanian age. In the North Sea, King 5.5.16. Fenestrella bellii zone et al.Ž. 1989 also recognizes the polonica zone This distinctive zone is defined on the presence of Ž.FCS18 , but these authors extend the zone below a small, pillbox diatom with an oval cross-section, the range of the nominate species down into the and sharp periphery, named Fenestrella bellii n. sp. Coniacian. Ž.Appendix B; Figs. 5 and 7c . It may occur in floods, accompanied by rare to common deep water agglutinated foraminifers, and rare to common sphericalr 5.5.15. Inoceramus LCO zone lenticular radiolarians. The following taxa have been This zone contains the following characteristic observed in assemblages assigned to this zone: eventŽ. Figs. 5 and 7c : Fenestrella bellii n. sp. LO Inoceramus LCO: This zone is recognized from a sphericalrlenticular radiolariansŽ. rare to common relative abundance of Inoceramus needles that con- Rzehakina epigona LO stitute the first carbonate rich interval downhole Haplophragmoides aff. walteri LOŽ sensu Kamin- following a thick, siliciclastic Campanian section, ski and Kuhnt, 1990.Ž rare . with pyritized diatoms, deep water agglutinated Spiroplectammina naÕarroana 64 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 65

Trochamminoides spp. Other dinoflagellate cyst taxa that have their aver- Deep water agglutinated foraminifers, undifferen- age last occurrence in this zone include Paleogleno- tiated. dinium cretaceum, while Chatangiella niiga, C. Remarks: Above the Inoceramus LCO zone, an granulifera, Xenascus ceratoides and Trithyrodinium interval occurs in many wells with a small, morpho- suspectum LCO on average disappear in the lower- logically distinctive, pyritized diatom, informally most part of the immediately overlying zoneŽ. Fig. 5 . named Diatom sp. H, and here assigned to the new Age: Early Campanian. species Fenestrella bellii Ž.see Appendix B . Spheri- Environment: Dysaerobic, middle to upper calrlenticular radiolarians may be common, and so bathyal. are coarse agglutinated benthic foraminifers with Occurrence: Widespread, offshore Norway; in- organic cemented tests. The latter include Karre- cluding the Voering Basin. rulina conÕersa, Haplophragmoides aff. walteri Correlation: This zone probably largely corre- Ž.sensu Kaminski and Kuhnt, 1990 , Spiroplectam- lates to the `Unnamed' zone FCN18 of King et al. mina naÕarroana, Paratrochamminoides olszewska, Ž.1989 with exclusively non-calcareous, agglutinated P. mitratus, Trochamminoides subcoronatus, and foraminifers in the northern North Sea, assigned to Rzehakina epigona, all of which may extend slightly lower Campanian, in agreement with our superposi- higher in the section, above this zone. Rzehakina tional zone data and the upper range of the dinoflag- epigona has a high varianceŽ. Fig. 9 , and is not a ellate cyst P. cretaceum inŽ. Costa and Davey, 1992 . reliable correlation event; although offshore Norway In the southern North Sea, in UK and in NW Ger- it disappears on average in the F. bellii zone. many this stratigraphic interval is probably shallower Various taxa of Trochamminoides, listed above, marine, and hence dominated by carbonates; it is in the North Atlantic underwent an evolutionary zoned with Stensoeina taxa and planktonic radiation in the early Campanian, an `event' clearly foraminifers. recorded offfshore Norway in flysch-type, bathyal The lower Campanian Goesella rugosa zone of strata. In exploration reports, the distinct Trocham- Geroch and NowakŽ. 1984 first recognized in the minoides taxa are commonly lumped under Para- Carpathian Trough, and based on the lower range of trochamminoides irregularis. The appearance and G. rugosa, is not recognized offshore Norway. The local disappearanceŽ or probably more correctly, the taxon is present in North Atlantic DSDP Sites, and in part of the stratigraphic range of the genus where its Zumaia, SpainŽ. Kuhnt and Kaminski, 1997 , but taxa become rare.Ž. is in Campanian strata Fig. 5 . In appears to be absent, offshore Norway. deeper bathyal settings, like in the Voering Basin, The diatom, and locally radiolarian-rich interval Gaudryina filiformis has its highest stratigraphic ex- in the Norwegian Sea wells, assigned to the F. bellii tension in this zoneŽ. cf. Geroch and Nowak, 1984 , zone may correspond to the biosilicious event in but maybe difficult to separate from Gerochammina western Tethys and North Atlantic, observed in the lenis. On Fig. 5Ž. left , the F. bellii assemblage forms upper part of anomaly 34 reversedŽ near the Santo- a distinct interval zone, separated with a large inter- nian±Campanian boundary. . This paleoceanographic fossil distance from the immediately overlying zone event is a faunal change at a number of localities in of Tritaxia dubia that includes the dinoflagellate the Atlantic and western TethysŽ. Kuhnt et al., 1998 Trithyrodinium suspectum LCO at its base. coeval with a change from well-oxygenated reddish

Fig. 9. Summary of event variance analysis results for the Cretaceous optimum sequence of Fig. 5. To the left, the optimum sequence of Cretaceous microfossil events in 31 wells, offshore mid-Norway, where each event occurs in at least seven out of 31 wells; N is the number of wells sampled to calculate the S.D. per event Ž.N) or s7 , and S.D. is the standardized deviation from the line of correlation in each well. The average standard deviation of 1.8903 is the sum of all S.D.'s, divided by the total number of events Ž.s72 in the optimum sequence. The asterisk behind events indicates an event with a S.D. that is smaller than the average S.D. From event S.D. theory it follows that events with a below average S.D. correlate the same relative stratigraphic level more faithfully from well to well than events with a higher S.D. The regional correlation application of this is discussed in the text; see also Fig. 10a±c for further details. 66 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 claystones below, to greenish, radiolarian-rich sedi- spectabilis, which regionally re-appears in the upper ments above. This event has been termed Ocean Paleocene, and Arenoturrispirillina. Anoxic Event 3Ž. OAE 3 , although there is no The assemblage, together with the dinoflagellates evidence for truly anoxic conditions at the seafloor. listed below forms a distinctive interval zone in Fig. It reflects a time when surface productivityŽ and 5Ž. left , that is assigned a middle to late Campanian hence sea-floor organic flux. was comparatively high. age, based on the upper stratigraphic range of T. dubia Ž.sT. subparisiensis in Geroch and Nowak 5.5.17. Tritaxia dubia zone Ž.1984 . This zone is defined on the presence of Tritaxia Dinoflagellates are abundantly present, and in- dubia LOŽ. Figs. 5 and 7c , widely reported under a clude the average last occurrences of Trithyrodinium variety of namesŽ. see below . The following taxa suspectum LCO, T. suspectum, T. castaneum, have been observed in assemblages assigned to this Chatangiella niiga, C. granulifera, C. ditissima, zone: Spongodinium delitiense FO, and Palaeohystri- Tritaxia dubia LO chophora infusorioides, which together belong in Pseudogaudryina pyramidata LOŽ. rare middle and upper CampanianŽ Costa and Davey, Marsonella crassa 1992. . Using dinoflagellates, the LCO of T. suspec- Trochamminoides spp. LCO tum and Chatangiella niiga LO may be used to Spiroplectammina dentata Ž.rare distinguish a lower part of the T. dubia zone, middle Spiroplectammina naÕarroana Ž.rare CampanianŽ. Fig. 5 . Spiroplectammina spectabilis Age: Middle to late Campanian. Arenoturrispirrilina sp. Environment: Upper bathyal. Caudammina oÕulum Occurrence: Widespread and relatively thick, Caudammina oÕuloides offshore Norway. Remesella Õarians Correlation: After early Campanian, North At- Glomospira spp. lantic low diversity assemblages with Glomospira Coarse agglutinated benthic foraminifers LCO increase in diversity. New species belonging to the Epistomina supracretacea genera Caudammina, Haplophragmoides, Para- Globorotalites michelinianus trochamminoides, and Rzehakina are observed for Gyroidinoides beisseli LO the first time, as are calcareous-cemented aggluti- GaÕelinella usakensis LO nated forms belonging to the genera Arenobulimina, Red coloured planktonic foraminifers including ClaÕulinoides, Dorothia, Goessella, Marsonella, Hedbergella, Rugoglobigerina, Marginotruncana, Remesella, and Spiroplectinata. The latter assem- Archeoglobigerina. blage change marks an Atlantic-wide drop in the Remarks: In the southern part of the region level of the Carbonate Compensation depthŽ. CCD to studied, calcareous foraminifers may include abun- a depth of below 5000 m, resulting in the deposition dant planktonics, as listed above, often stained red. of the marly Crescent Peaks member of the Planta- Northward, calcareous foraminifers become rare, and genet FormationŽ. Jansa et al., 1979 . At this time, the the zone is more difficult to define, particularly when distinctive `flysch-type' and calcareous-cemented overlying Paleocene and Maastrichtian strata also agglutinated taxa become common, and their overall contain coarse agglutinated foraminifers. On average diversity increase in the North Atlantic and also in though, the latter disappear stratigraphically upward the Norwegian Sea, reflected in the composition of together with other taxa listed above, one of the most the Tritaxia dubia zone. This faunal turnover coin- typical which is Tritaxia dubia. This taxon likely is a cides with major changes in watermass properties, junior synonym of Tritaxia subparisiensis ŽGrzy- owing to increased deep-water productivity from bowski. and in reports may hide under junior syn- high-latitude sources, cooling and increased ventila- onyms like Pseudogaudryina capitosa, Tritaxia tri- tion of deep waters, and higher upwelling rates. carinata and T. capitosa. Typically, several Spiro- Active watermass communication through the Scot- plectammina taxa may be present, including S. land±Greenland gatewayŽ. Fig. 1b , existed between F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 67 the proto Norwegian sea and the North Atlantic stratigraphically upward. A similar pattern was ob- Ocean. served also by King et al.Ž. 1989 , suggesting the The Tritaxia dubia zone correlates to the Tritaxia taxon is in fact time transgressive southward. capitosa zone, FCN19 of King et al.Ž. 1989 , also In few wells, the upper part of the R. szajnochae assigned toŽ. middle to upper Campanian. King et al. zone shows a bloom of Globigerinelloides Õolutus Ž.op. cit. also refers to the red claystones, assigned to Ž.Fig. 7b , that may constitute a stratigraphically use- the upper part of the zone, that stain the foraminifers ful subzone, and requires study. red. The claystone corresponds to the `Upper Red Organic walled microfossils that have their aver- Unit' of the Flounder Formation in Moray Firth and age last occurrence in this zone include Odonto- `Pink Chalk' in the central North Sea. chitina costata and Aquilapollenites spp.Ž. Fig. 5 , typical for lower MaastrichtianŽ Costa and Davey, 5.5.18. Reussella szajnochae zone 1992. . This zone is defined on the LCO of Reussella Age: Probably mostly early Maastrichtian. szajnochae Ž.Figs. 5 and 7b . Other key events in- Environment: Deep neritic to upper bathyal. clude Rugoglobigerina spp., Globigerinelloides Õo- Occurrence: Widespread, offshore Norway. lutus, and Globotruncanella haÕanensis Ž.Fig. 7c Correlation: The R. szajnochae zone correlates The following taxa have been observed in assem- to the lower part of zone of the same nameŽ FCN20 blages assigned to this zone: p.p..Ž. in the northern North Sea King et al., 1989 . In Reussella szajnochae LO the Carpathian belt, sediments of the same age con- Caudammina oÕulum tain Caudammina oÕulum gigantea, a lower bathyal Globotruncanella haÕanensis to abyssal taxon not observed offshore Norway. The Rugoglobigerina tradinghousensis( southern area reason for its absence is that no sediments of that only) larger paleo waterdepth have been sampled. The Rugoglobigerina rotundata taxon is known from the North Atlantic, and the Rugoglobigerina spp. Faeroer BasinŽ D. van den Akker, pers. comm., Globotruncana arca Ž.south only 1997. . Globotruncana mariei Ž.south only Globotruncanella intermedia 5.5.19. Pseudotextularia elegans zone Globigerinelloides Õolutus This distinctive zone is defined on presence of Hedbergella spp., including H. holmdelensis Pseudotextularia elegans LOŽ. Figs. 5 and 7b ; other BoliÕinoides draco miliaris Ž.southern area only key taxa that may be present include Rosita contusa, Deep water agglutinated foraminifersŽ more com- Rugoglobigerina spp., Racemiguembelina Õarians, monly found northward. and Brizalina ex. gr. incrassata Ž.Fig. 7b . The fol- Brizalina ex. gr. incrasssata lowing taxa have been observed in assemblages as- Anomalinoides Õelascoensis signed to this zone: Stensioeina pommerana Pseudotextularia elegans GaÕelinella beccariiformis. Abathomphalus mayaroensis Remarks: The zone of Reussella szajnochae is Rosita() Globotruncana contusa easily recognizable from the average LO of its dis- Rugoglobigerina rugosa Ž.includes acme tinctive, nominate species, which generally is present Globigerinelloides Õolutus Ž.includes acme with few specimens only in the wells samples exam- Pseudoguembelina excolata ined, but occurs widespread. Associated calcareous Racemiguembelina Õarians benthic taxa and planktonics are listed above. In Stensioeina pommerana southern wells many more taxa occur, that require Brizalina ex. gr. incrassata study. In a few of these southern wells, isolated Heterohelix spp. specimens of the nominate taxon range in the overly- Hedbergella spp., including H. monmouthensis. ing zone of Pseudotextularia elegans. It is not clear Remarks: As far as can be determined, this zone if R. szajnochae is in fact reworked or extends is largely missing in northern wellsŽ together with 68 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Danian, lower Paleocene. ; it may be condensed with older along a geographic gradientŽ time transgressive lower Maastrichtian strata southward. Where it is behaviour. . Hence, the method assists with identifi- present, it is rich in calcareous taxa, predominantly cation of faithful stratigraphic marker events in cor- planktonics. The lower part of the zone harbors relation, but also points to events that are time acmes or LCO levels of Rugoglobigerina rugosa transgressive, for example as a function of gradual andror Globigerinelloides Õolutus which may con- paleoceanographic or paleobathymetric change. stitute 50±90% of specimens observed. These levels The method proceeds as follows: Individual well may constitute a subzone. More study, particularly of sequences are compared to theŽ. scaled optimum cores is desirable to understand the successive records sequence using curve fitting techniques to calculate a of events in this zone. line of correlation, and obtain estimates of the spread It is peculiar that Abathomphalus mayaroensis, of the events Ž.sdeviation , relative to the best fit where observed does not seem to occur at the top of line. For example, if an event occurs in 15 wells, a the zone, but rather at its base or even lower. It is not best fit line is calculated for the individual event clear from the data if such occurrences are due to sequence in each of the fifteen wells relative to the caving, or indeed represent an older record. Di- optimum sequence. Hence, 15 event deviations to the noflagellate cysts present in the zone include Cero- best fit line are known, one for each well in which dinium diebeli and Palynodinium grallator LO, in- the event occurs. These 15 deviations are combined dicative of upper MaastrichtianŽ Costa and Davey, in an average event variance. Or to say it in a more 1992. . formal manner: The frequency distribution of events Age: Late Maastrichtian. may be computed by measuring the differences be- Environment: Deep neritic to upper bathyal. tween the knownŽ. observed event positions and Occurrence: The P. elegans zone is largely rec- their line of correlation Ž.scurve expected values, ognized in the southern part of the area studied, and yields the variance and standard deviation offshore Norway. As may be seen from Fig. 2, a ŽD'Iorio and Agterberg, 1989; Gradstein and Agter- widespread Maastrichtian±Danian hiatus is present berg, 1998. . in part of the study area, particularly in its northern A small standard deviation indicates a good part, offshore mid-Norway. We postulate that this marker event in correlation, and a large standard hiatus is due to shoulder uplift during `break-up', deviation a bad one. This is because an event with prior to the onset of Paleogene seafloor spreading in small standard deviation is close to its expected the Norwegian Sea. position on the lineŽ. curve of correlation in all Correlation: The P. elegans zone correlates to wells. It would be possible to correlate an event with the North Sea wide P. elegans zone of King et al. zero mean and zero standard deviation with absolute Ž.1989 , and the GaÕelinella danica and P. elegans certainty between wells. On the other hand, an event zones of KochŽ. 1977 in NW Germany, correlative with large variance occurs much lower or higher to the junior and casimiroÕensis belemnite zones than expected in one or more wells. Graphical repre- Ž.Late Maastrichtian . sentation of differences between observed and expected positions at well locations, e.g., on a geographic map, may show that the large variance of an 6. Variance analysis and paleoceanography event is due to time transgressive behaviour. Thus variance analysis can be useful for tracking the time Variance analysis of fossil events enhances in- transgressive behaviour of events. sight in their regional occurrences. The analysis Application of RASC variance analysis to a fore- compares the relative position of fossil events in runner of the present biozonation, was used by Grad- individual wells to their average position in the stein and AgterbergŽ. 1998 to demonstrate that the RASC optimum sequence, while using that average lower Cenomanian Lange sands, and the middle level as a stratigraphic reference. With this reference Cenomanian to Turonian Lysing sands, offshore level, it is possible to trace events over all wells, and mid-Norway, are not seismic markers, or well log find out if they become systematically younger or `sheet sands' in a correlative sense, but showed a F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 69 more complex correlation patterns than hitherto as- much lower. Our original data, prior to re-analysis sumed. The conclusion is in line with the sedimento- showed well 20 to be in line with the trend of other logical interpretation that the sands are debris flow southern wells. This selective picking of events prac- and turbidite sandsŽ. T. Saether, pers. comm., 1996 . tise appears unwarranted, since biostratigraphers may In this study, we will again look at some fossil `know' the age before the zone, turning stratigraphy events associated with these sands, and also group up-side down, and hampering detailed and reliable the Cretaceous zonal events in four broad groups, correlations. using variance analysis to rate potential isochronous The question is why this time transgressive be- correlation. haviour of these taxa, and here answers are scarce. One possibility might be that both dinoflagellate taxa 6.1. Lithosphaeridium siphoniphorum thrive in a more open marine, pelagic carbonate environment, as found in western Europe throughout The optimum sequence of Fig. 9 allows differenti- Cenomanian±Turonian. According to Costa and ation between more reliable, and less reliable events DaveyŽ. 1992 E. spinosa in western Europe extends for well to well correlation. To the left in Fig. 9 is well into middle Cenomanian and L. siphoniphorum the optimum sequence of Cretaceous microfossil in early Turonian. Offshore Norway, the flood of events, where each event occurs in at least seven out calcareous planktonic foraminifers only extends from of 31 wells; N is the number of wells sampled to late middle Albian into early CenomanianŽ. Fig. 12 . calculate the S.D. per event Ž.N) or s7 , and S.D. Possibly, the distribution of the dinoflagellate cysts is the standardized deviation from the line of correla- is linked to the calcareous flux and has limited the tion in each well. The average standard deviation of ecological niche of the two dinocysts taxa from 1.8903 is the sum of all S.D.'s, divided by the total middle Cenomanian time onward. It led to a drastic number of events Ž.s72 in the optimum sequence. reduction in their population density, and makes An asterisk behind events indicates an event with an detection of the upper part of their total stratigraphic S.D. that is smaller than the average S.D. for an range spotty. For well stratigraphy, emphasis on the optimum sequence of events. last consistent stratigraphic occurrenceŽ. LCO event The first item that stands out in Fig. 9, is that of these taxa might be in order. Lange and Lysing reservoir sand intervals from E. spinosa in lower Cenomanian to Bulbobaculites problematicus in Turonian created higher S.D. val- 6.2. Hedbergella delrioensis LCO ues; this is to be expected, if we take into account increased frequency of reworking, and problems in The first and last common, and consistent pres- sampling complete stratigraphic ranges where sandy ence of the planktonic foraminifer Hedbergella del- intercalations occur In this respect, it is not surpris- rioensis Ž.Plate I, Figs. 1±12 , and the last common ing that presumed regional marker dinoflagellates and consistent occurrence of H. planispira ŽPlate II, like E. spinosa, L. siphoniphorum have high S.D. Figs. 1±12.Ž. have well below average S.D.s Fig. 9 . values, and non-normal histograms of stratigraphic The local flood of specimens reflects considerable deviationsŽ. Fig. 10a ; the same is true for M. mem- marine transgression, with slow sedimentation, and braniphorum. One contributing factor, other than influence of Atlantic surface watermass along the frequently reworked tops, is that L. siphoniphorum, eastern side of the proto Norwegian Sea. On the observed in 19 wells, appears to be time transgres- other hand, a perusal of samples we collected in sive, ranging into younger strata southwardŽ Fig. Aptian through Albian dark shale levels in NW 10a. ; the same may be true for E. spinosa, observed Germany also shows many levels with monotypic in 13 wellsŽ. Fig. 10a . The single well where this planktonic floods of Blefuscuina, Blowiella, Glo- time transgressive behaviour appears reversed is well bigerinelloides and Hedbergella. It suggest that these 20Ž. 35r3±4 , but in this well palynology consul- simple, non-keeled planktonics thrive in relatively tants, being made aware of this time transgressive small bathyal, boreal basins, as long as salinity is `problem', re-analysed the well and picked the events normalŽ there are many ammonites in the NW Ger- 70 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 man basin. , sedimentation rates low, and watermass evidently is a lull in sand sedimentation. The LCO fertility enhanced by abundant organics input, hence event was observed in 14 wells, has a low S.D. of the dark shales. As long as the basins are connected 1.118 and a normalŽ. Gaussian distribution of well to the Tethys and Atlantic oceans to enhance pelagic deviationsŽ. Fig. 10c . In the 35 block area, offshore incursions, will these simple planktonics invade. Such SW Norway, the H. delrioensis FCO event occurs invasions also are known from the austral Gearle closely above the top Albian as defined from the LO shales, Aptian of NW Australia, and the mid-Creta- of OÕoidinium scabrosum, whereas the H. delrioen- ceous of the Western Interior, northern USA. Niches sis LCO event marks the top of the H. delrioensis for these simple planktonics may have been less LCO zoneŽ. lower Cenomanian , that here also in- oceanic and more continental margin watermasses, cludes the LO's of Rhombodella paucispina, Plec- possibly in response to too high salinity of open torecurÕoides alternans and LingulogaÕelinella oceansŽ. W. Hay, pers. comm, 1998 in mid-Creta- jarzeÕae. In terms of local sands, the H. delrioensis ceous. FCO event in the south appears abruptly above It is interesting that another simple planktonic, massive Albian sands, also named Agat sands, laid Globigerinelloides gyroidinaeformis, that from its down under dysaerobic, bathyal conditionsŽ see Sec- smooth wall and slightly irregular planispiral coiling tion 7. , and the LCO event occurs at the top of lower might be a benthic during part of its life cycle, in Cenomanian, above some more local lower Cenoma- fact is common in one well, offshore NorwayŽ Fig. nian sands. Hence, the stratigraphic range of com- 8.Ž. just below also cored levels where H. planispira mon to abundant Hedbergella delrioensis is above and H. delrioensis appear. Why this taxon is not Agat sands, and below Lysing sandsŽ. Fig. 14 . known from NW Germany is unclear; it is frequent What is insightfull, is to compare the planktonic during a brief interval ŽG. gyroidinaeformis zone, ranges in UK, NW Germany and offshore Norway mid Albian; Fig. 6a. in the Viking Graben and also Ž.Fig. 11 . The boreal planktonic foraminiferal acmes, known from more Tethyan localities in France and offshore mid-Norway, correlate to similar acmes in offshore Eastern Canada. Its short stratigraphic range NW Germany and UKŽ. Hart, 1993; Prokoph, 1997 . and wide distribution are arguments in favour of it Also shown are the standard ammonite and plank- being planktonic. tonic foraminiferal zonations for the interval, and the In Gradstein and AgterbergŽ. 1998 , we first regional RASC zonation. The prominent Globiger- brought forward that H. delrioensis LCO, offshore inelloides bentonensis acme in NW Europe is barely mid-Norway is useful to separate more scattered recognizable further north, offshore Norway, which Lange sands, assigned to lower Cenomanian, from region is peripheral to its paleogeographic distribu- more massive Lysing sands, assigned to middle tion. Why the hedbergellids dramatically decline Cenomanian±Turonian. The planktonic LCO event abundance near the boundary of lower and middle

Fig. 10.Ž. a Deviations from expected stratigraphic position and histograms of stratigraphic deviations for dinoflagellate cysts events Litosphaeridium siphoniphorum and Epelidosphaeridia spinosa. These events have high S.D. values and non-normal frequency distributions which indicate low value as zonal markers. One factor, other than common reworking of these events in the often sandy Cenomanian interval that makes it difficult to pick them in wells, is that the LO's of L. siphoniphorum and E. spinosa maybe time transgressive, ranging younger southwardŽ.Ž. see text . b Deviation from expected stratigraphic position and histogram of stratigraphic deviations for Hedbergella delrioensis LCO, a calcareous planktonic LCO events that reflect oxic watermass conditions, relatively high fertility and slow sedimentation. The event, observed in 14 wells, has a low S.D. 1.118 and a tendency to a normal histogram of stratigraphic deviations. Other planktonic and some calcareous benthic eventsŽ. of similar stratigrahic importance with low standard deviations and a normal histogram are from stratigrahically younger to older, Rugoglobigerina rugosa, Globigerinelloides Õolutus, Reussella szajnochae, Red coloured planktonics, Inoceramus needles LCO, Stensioeina polonica and Dicarinella imbricata.Ž. c Deviation from expected stratigraphic position and histogram of stratigraphic deviations for agglutinated benthic foraminiferal fossil events that reflect dysaerobic watermass conditions and fine grained, low carbonate, mudstone substrate. These events are Tritaxia dubia, Deep water agglutinated foraminifers LCO, and UÕigerinammina una Ž.not shown , with low standard deviations of 1.254, 1.358 and 1.445, respectively, and normal histograms, which indicates their value as zone markers. The Campanian deep water agglutinated foraminifer event, although easy to recognize in wells, probably is time transgressive within that stage. F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 71 72 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Fig. 10Ž. continued . F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 73

Fig. 10Ž. continued . 74 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Fig. 11. Boreal planktonic foraminifera acmes, offshore mid-Norway, correlated to similar acmes in NW Germany and UKŽ Hart, 1993; Prokoph, 1997. . Also shown are the standard ammonite and planktonic foraminifer zonations for the interval, and the regional RASC zonation. The prominent Globigerinelloides bentonensis acme in NW Europe is barely recognizable further north, offshore Norway, which region is peripheral to its distribution. Reasons for the acmes are discussed in the text.

Cenomanian is not certain, but several lines of evi- the subsequent hiatus or lag represents a rise after a dence bear on the issue. sudden lowstand. Hence, we propose that this hiatus Firstly, in the 35 block area the abrupt reduction is coeval with the Rouen hardground complex in in hedberghellidsŽ. the H. delrioensis LCO event is France, the mid-Cenomanian non-sequence in south- followed by a level with abundant brown, sideritic ern UKŽ. Hardenbol et al., 1993 , and the large hiatus concretions. The latter suggests that a local hiatus or at the boundary of lower and middle Cenomanian in a condensed interval is present at that level, probably NW Germany, e.g., in the Baddeckenstedt areaŽ Mut- of early middle Cenomanian age. Although no re- terlose et al., 1997. . The hiatus may be linked to a gional sequence stratigraphic analysis is done, we tectonic uplift andror tilt of basin margins around postulate it is reasonable to infer that the H. delri- the early to middle Cenomanian boundary, followed oensis LCO event is indicative of the top of a by renewed gravity-flow sand deposition, offshore transgressive or highstand sequence interval, and that mid-Norway from middle Cenomanian onward. The F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 75

Fig. 12. Foraminiferal trends in the cored interval of Albian to earliest Cenomanian age in well 35r3±4, Agat area, offshore Norway.

sand lithology severely dilutes the planktonic record ceanographyŽ. Figs. 2, 5 and 11 . Firstly there are in samples, but other, not understood reasons might calcareous planktonic LO and LCO events that re- prevail to curtail proliferation of planktonics in mid- flect oxic watermass conditions, relatively high fertil- dle to late Cenomanian. Detailed studies of cores ity and slow sedimentation. These events include may reveal global dysaerobia to play a role in the Rugoglobigerina rugosa and Globigerinelloides Õo- seaway, as surmised also from the CrT boundary lutus, red coloured planktonics, Inoceramus needles gamma spike event in the brittonensis zoneŽ see LCO, Dicarinella imbricata, and Hedbergella delri- above. . Not until early to middle Turonian time do oensis LCOŽ. Fig. 5 . All of these events occur in rich, and more diverse planktonic assemblages re-ap- many wellsŽ except `Red coloured planktonics' that pear, offshore Norway. is confined to eight of the southern wells, and D. imbricata., have low standard deviations compared 6.3. Four groups of eÕents to the average S.D. of 1.8903Ž. Fig. 9 , and histograms of stratigraphic deviations that are relatively Before we discuss correlation of low variance normal in shapeŽ. Fig. 10b . The same holds for the events, we like to present some thoughts on a broad benthic foraminiferal events Reussella szajnochae classification of zonal events relative to paleo- and Stensioeina polonica. Hence, these commonly 76 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 observed, oxic watermass events are considered reli- siphoniphorum, M. membraniphorum, and E. able zone markers. spinosa. The latter four events have high S.D. values Secondly, there are agglutinated benthic events of 2.068, 2.066, 3.024, and 2.531, respectivelyŽ Fig. that reflect dysaerobic watermass conditions, and 9. , and skewed, and not normal histograms of strati- fine grained, low carbonate, mudstone substrate. graphic deviations. This indicates low value as zonal These events are Tritaxia dubia, coarse agglutinated markers. As discussed above, a factor, other than deep water foraminifers LCO, and UÕigerinammina common reworking of these four events in the often una, with low S.D.'s of 1.254, 1.358 and 1.445, sandy Cenomanian interval that makes it difficult to respectivelyŽ. Fig. 9 , and normal histograms of pick them in wells, is that the LO's of L. si- stratigraphic deviations, which indicate their value as phoniphorum and E. spinosa may be time transgres- zone markers. The Campanian coarse agglutinated sive, ranging younger southward. foraminifers LCO event generally is easy to recognize in wells. It may be slightly time-transgressive, 6.4. Correlation but stratigraphic resolution is limited in the upper part of Campanian. As discussed earlier under the In geologic correlation it is common practise to Tritaxia dubia zone, the coarse agglutinated assem- evaluate stratigraphic resolution in terms of the num- blage reflects an Atlantic-wide drop in the level of ber of events per stratigraphic interval. If a zonation the carbonate compensation depth. Active watermass is made up of many closely spaced events, or if wells communication through the Scotland±Greenland are tied with many closely spaced parallel lines we gatewayŽ. Fig. 1b , existed between the proto Norwe- assume high resolution in relative geologic time. gian sea and the North Atlantic Ocean. This evaluation ignores the fact that stratigraphically Thirdly, there are siliceous planktonic events that successive individual events or tie lines might have reflect high watermass fertility. These events are stratigraphic uncertainties attached far in excess of Fenestrella bellii n. sp. and sphericalrlenticular ra- the displayed stratigraphic distance between them. diolarians, with fairly low S.D. values of 1.341 and True resolution comes from an evaluation of strati- 1.521Ž. Fig. 9 . The histograms of stratigraphic devia- graphic distances between events, and an estimation tions are normal, which suggests that the events are of stratigraphic standard devations on individual coeval over the many wells where they are observed. event positions. The radiolarian bloom event may be difficult to pick Fig. 13 shows correlation in eight wells of some in wells, since scattered radiolarians occur also in zonal events, with well below variance, of Albian stratigraphically younger levels that may be mistaken through Maastrichtian age. The wells are arranged for this event. Differences in sedimentation rates from northŽ. right to south Ž. left . Errorbars on calcu- between wells also tend to obscure the event. In the lated most likely event positions in the wells show North Atlantic, greenish radiolarian-rich sediments 95% confidence limit. The correlation diagram is appear near the Santonian±Campanian boundary, flattened on event 16ÐH. delrioensis LO. This event suggesting that it is a useful regional stratigraphic occurs in the W. brittonensis zone, upper middle to marker, offshore Norway, particularly if sediments upper Cenomanian, just below the CrT boundary would be cored. gamma spike, discussed under the W. brittonensis A fourth category of events are dinoflagellate zone in the previous section. Other events in the cysts that are extensively used for Cretaceous well diagram include from younger to older: 29ÐReus- stratigraphy, but are of variable stratigraphic quality. sella szajnochae, 255ÐTrithyrodinium suspectum These events include Trithyrodinium suspectum LCO, 370ÐFenestrella bellii n. sp., 330ÐInoc- LCO, Heterosphaeridium difficile LCO, Endocer- eramus needles LCO, 82ÐHeterosphaeridium diffi- atium dettmaniae, Litosphaeridium siphoniphorum, cile LCO, 212ÐHedbergella delrioensis LCO, 93 Maghrebinia membraniphorum, Epelidosphaeridia ÐOÕoidinium scabrosum, and 61ÐUÕigerinam- spinosa, OÕoidinium scabrosum and Apteodinium mina una n. sp. These events have low S.D. values grande. The events have low S.D. values and normal and normal histogramsŽ. Figs. 9 and 10 ; the length of frequency distributions, except for E. dettmaniae, L. the errorbars on most likely event position in Fig. 13 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 77 - LO. Hetero ons in the wells and event Hedbergella delrioensis needles LCO, 82Ð orway. Wells are arranged from Inoceramus n. sp. These events have low S.D. values and n. sp., 330Ð igerinammina una Õ U Fenestrella bellii , and 61Ð LCO, 370Ð oidinium scabrosum Õ O LCO, 93Ð Trithyrodinium suspectum , 255Ð Hedbergella delrioensis Reussella szajnochae LCO, 212Ð Ž. Ž. Ž. normal histograms Fig. 9 ; the length of the errorbars on most likely event position is a function of the original stratigraphic scatter of event positi variances. Other events include: 29Ð sphaeridium difficile north right to south left . Errorbars on most likely event positions in the wells show 95% confidence limits. The diagram is flattened on event 16, Fig. 13. Albian through Maastrichtian biostratigraphic correlations, using foraminifer and dinoflagellate events in eight wells, offshore mid-N 78 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 LCO level, are ty flow sands. The reen and red coloured Hedbergella c levels; black lines are from ith slow sedimentation. The sands levels, the Lange sands, and the sands above the LCO event Santonian are coloured red, and are considered flooding surfaces FS . Hedbergella Inoceramus Ž. FCO and LCO events Lower Cenomanian , and the FCO level are the Agat sands; the sands between the two Ž. Ž . Ž. Ž. Hedbergella correlation lines are from events that have below average stratigraphic standard deviation, and are thought to each track best the same stratigraphi Fig. 14. Correlation of events in the optimum sequenceevents and zonation that of have Figs. 5 above and average 6 in stratigraphic Albian through standard Santonian deviation strata in five and wells, offshore hence Norway. are G less certain in correlation, and show some cross-overs ; yellow-gravi Lysing sands. Hedbergella delrioensis These events represent reliable regional correlation levels, with below average S.D., that reflect considerable marine transgression, together w below the F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 79 is a function of the original stratigraphic scatter of Log traces are gamma ray, and sonicrneutron den- event positions in the wells, and event variances. sity. The first and last common to abundant occur- In most cases, the error bars are relatively small, rences of the planktonic foraminifer H. delrioensis and indicate that the events are well constrained in Ž.FCO and LCO events , and Inoceramus LCO also the wells. In few cases were error bars are larger, have well below average S.D., and are coloured red this reflects scarcity of fossil data in the wells, with on Fig. 14. The red events reflect considerable ma- considerable scatter in that data also. Other parame- rine transgression, together with slow sedimentation. ters, like well logs and lithologic trends will be In Fig. 13, the Hedbergella LCO event is 212, and needed to further constrain correlations, but with the the Inoceramus LCO event 330. RASC program initial fossil correlations are easily It may be readily observed in Fig. 14 that sand and rapidly accomplished, and the simultaneous correlations are relatively complex, but are tracked colour graphics display allows to evaluate principal by green and red markers. None of the green and red correlation trends, prior to import in well log, and markers cross-over, although some black ones doŽ as seismic subsurface displays. expected. . At the outset of this exercise geologists In Fig. 14, variance data on fossil events are used had stratigraphically lined up the sands between to create a different, but effective type of correlation wells much more than appears likely from the micro- plot. Here variance analysis data are utilized to fossil correlation data. Hence, prospectivity may have correlate the Cretaceous turbiditic sands in five wells, degraded but the correlation trends are more in line offshore mid and southwestern Norway. These sands of what is expected with turbiditic sands It is beyond are difficult to track on seismic, and regionally have this study to enlarge on the geologic implications of a complex architecture. The stratigraphic interval these findings, but the point may be made that displayed in the figure covers upper middle Albian correlation of low S.D. events from RASC analysis through lower Campanian. Initially, correlation of all enhances insight in well to well correlation, in search zonal events as observed in the wells produced a of stratigraphic traps. diagramŽ. not shown with many reasonably concor- dant correlation lines, but also a number of lines that crossed each other, suggesting uncertainty in local 7. Paleobathymetry and sequence breaks point correlations. It would be possible to calculate most likely event positions from a crossplot between In this section, we will outline principal trends in zonation and well data, as achieved in Fig. 13. lower and middle Cretaceous paleobathymetry, its Correlation of such interpolated event positions pro- underlying reasons, and microfossil criteria utilized duces parallel tie lines between wells. The problem to assign paleo waterdepth in exploration wells. De- with such a procedure is that considerable geologic tails of upper Cretaceous paleobathymetry await more information must be taken into account to avoid core data, including information from the Voering `nonsense' correlations across hiatusses and uncon- Basin, where massive Campanian gravity flow sands formities not readily seen from event data only. indicate `central' depocentres in the seaway between Also, events are not ranked as `good and bad' track- Norway and Greenland. ers of the same stratigraphic level, unless additional information is taking into account, like event variance, shown in Fig. 13 as error bars. 7.1. Lyr formation, upper HauteriÕian±lower Bar- A simpler and more direct manner of proceeding remian with event correlation between the wells is to tie the wells together with the observed rather than interpo- One of the most outstanding features of the Lower lated depth of the fossil events, and indicate with a Cretaceous microfossil record, offshore southwest colour which events have below average S.D. values. and mid Norway is the abrupt appearance of diversi- In Fig. 14, these low S.D. events are coloured green fied foraminiferal assemblages that characterise the and red, whereas events with above average S.D. reddish, calcareous sediments of the Lyr Formation, values are in black. Gravity flow sand are in yellow. assigned to the Protomarsonella kummi, Falso- 80 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 gaudryinella praemoesiana and F. xenogena zones, tomina caracolla, of shallow marine and oxic water- upper Hauterivian through lower Barremian. The Lyr mass character. This well was not included in the sediments follow upon an extensive hiatus separating RASC zonation due to the presence of many strati- middle or late Jurassic from early Cretaceous strata graphic gaps, and poor fossil recovery. Ž.Figs. 2 and 3 , during which Ž. hiatus period we postulate much land existed between Greenland and 7.2. Aptian±Albian shales and sands Norway. Multicoloured microfossil assemblages assigned Stratigraphically upwards in lower Cretaceous to the zones cited above and the Lyr Formation are well sections, in strata assigned to Aptian and Al- known from Andoya as mentioned earlier, and have bian, the microfossil assemblage changes dramati- now also been observed by us on Eastern Greenland. cally from below. It includes well-known deep-water The assemblages are generally fairly rich in calcare- agglutinated taxa like Caudammina crassa, Kalam- ous benthics like lenticulinids and other nodosariids, opsis grzybowski, Cribostomoides nonioninoides, Re- spirrilinids, Patellina, calcareous cemented aggluti- curÕoides spp., PlectorecurÕoides spp., and rare nated forms like Falsogaudryinella and textulariids. PseudoboliÕina. The assemblages also contains a fair Epistomina and Trocholina are mostly rare, while proportion of tubular, deep water agglutinated taxa smooth ostracods are common, and so are macrofos- such as Rhabdammina, Rhizammina, and Bathy- sil fragments. A more complete microfossil listing is siphon. There is little doubt that such assemblages, in Appendix A. known as they are from the Carpathian Trough, other This type of microfossil assemblage is typical for flysch basins and oceanic environments, are indica- relatively shallow marine, neritic and photic zone tive of bathyal conditions. Sediments are dark shales conditions, with oxic watermass. Dominant forms with minor amounts of carbonate, and gravity flow like Falsogaudryinella and Lenticulina possess in- sands during Albian time, in the southern part of the faunal morphologies that in modern oceans are dom- region. inant on the outer part of the neritic zone, passing Lower Cretaceous planktonic foraminifers are into upper bathyal. Few endemic taxa have been generally rare, but locally and temporally occur in observed. Water circulation must have been largely floods in Albian timeŽ and also in Aptian time anti-estuarine, allowing flushing of fresh-water input, southward, probably because of fewer hiatusses and keeping oxygenation high. Hence, the sediments there. , discussed in the previous chapter. The upper of the Lyr Formation represent a major circum Nor- part of middle and upper Albian locally also harbour wegian Sea transgression in Hauterivian to Bar- calcareous benthic taxa with Osangularia, GaÕe- remian time, with marine connections opening to linella, Pleurostomella, Epistomina and Gyroidina. both the Atlantic via the Scotland±Greenland gate- Again, the occurrence of these taxa fits in the inter- ways, and via the Viking Graben into NW Germany pretation that we are dealing with bathyal assem- Ž.Fig. 1a . blages. In few northern sites, it was observed that the The question is what caused the change from typical calcareous and oxic Lyr Formation assem- neritic to bathyal conditions, in mid-CretaceousŽ Fig. blages in Barremian time change into an almost 1a,b. . Hauterivian to Aptian sediments are mostly monotypic assemblage with Spirrilina, some am- thin, at maximum hundred meter or so thick, proba- modiscids, and common pyrite. Hence, we postulate bly reflecting slow, thermal subsidence, following that the open marine, oxic conditions locally may Jurassic graben formation between Greenland and have locally changed to become enclosed, lagoonal Norway, and further compaction of massive underly- with abundant organics input limiting oxygenation of ing Jurassic strata. It is possible that the limited bottom waters. sedimentation, in a slowly subsiding basin, might In one updip well site, 36r1±1, in the southwest- have sufficed to increase paleo waterdepth, as ob- ern portion of the study region, the benthic served. Mid-Cretaceous block-faulting is thought to foraminiferal assemblage correlative to Lyr Forma- have played an important roleŽ see below; Guy, tion assemblages northward, consists largely of Epis- 1992. , but another factor contributing to the increase F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 81 in sediment accommodation space, was the rise in benthic taxa, and the assemblage is interpreted as eustatically controlled sealevel in early through mid- reflecting dysaerobic conditions in a restricted basin. dle Cretaceous time. Estimates vary, but an increase The basin is open marine, but the lower water col- in paleo waterdepth in excess of 250 m may have umn is restricted, and beyond the influence of storm been the result from global sea-level riseŽ W. Hay, wave base. An bathyal, slope setting is likely, the pers. commun., 1996. . Hence, even if the sediment upper depth limit probably being upper bathyal as basins between Greenland and Norway were tectoni- generally interpreted for flysch-type assemblages cally passive, and without much sediment input, Ž.Gradstein and Berggren, 1981 . paleo waterdepth would have increased from neritic From 3507 to 3480 m, the agglutinated fora- to upper bathyal. With minor sediment input as miniferal assemblage decreases in diversity, and from observed, ongoing thermal subsidence, and the com- 3480 to 3473 mŽ. upper Albian , minor calcareous paction of underlying Jurassic strata, upper bathyal benthics appear, including rare Pleurostomella, tol- paleo waterdepths in Aptian to Albian time are in erant to dysaerobic conditions. Also at 3473 m hy- line with what we postulate independently from the drodynamic sorting of the assemblage is observed, microfossil assemblage. with either largely tubular, or largely discoidal An interesting feature in the Albian bathyal set- foraminiferal tests. This trend from 3507 m upward ting is the dramatic change from dysaerobic to oxic is interpreted as a decrease in waterdepth, decrease basin, clearly observed in several southern wells, in watermass restriction, and shallowing to wave-base e.g., in the 35 block areaŽ. Agat . There, Albian level. reservoir sand deposits were mapped by J. Nystuen It is not clear why from 3464 through 3411 m, Ž.pers. comm., 1995 as mass-flow deposits, including across the Albian±Cenomanian boundary, shale sam- turbidites, from several easterly point sources. The ples are barren of shelly microfossils; pyritisation paleo waterdepth may be interpreted from the does not seem to be an active cause of shell destruc- foraminiferal assemblages in the core samples of tion in this well site. Above 3411 m to the top of the dark shales interbedded with the sands in wells cored interval at 3400 m, lowermost Cenomanian, 35r3±2 and 35r3±4. Fig. 12 summarizes the the microfossil assemblage in the dark shales is 99% foraminiferal trend in the more proximal well 35r3± planktonic foraminifers, consisting of Hedbergella 4, during middle to late Albian, and earliest Cenoma- delrioensis, with rare H. planispira. Dark shales are nian time. less laminated than below, and we conclude that the The foraminiferal assemblage in dark, and often youngest shale sediment was laid down in an oxy- laminated shales between the mass-flow sands, are genated, open marine basin setting that might be dominated by agglutinating benthic foraminifers, re- deep neritic at maximum wave base level. sembling flysch-type fauna. Over 30 taxa are recog- As discussed earlier, such monotypic planktonics nized, and the assemblage is diverse in genera and flood also are reported from NW Germany, southern species, with many tubular taxa, like Rhabdammina, North Sea and UK, representing the same transgres- Rhizammina and Bathysiphon, and varying propor- sive, maximum flooding interval when watermass tions of Haplophragmoides, Cribrostomoides, Glo- conditions in the basins changed from dysaerobic to mospira, Ammodiscus, RecurÕoides, Psammo- oxic. sphaera, Reophax, PlectorecurÕoides, Falsogaudry- In the 35r3±2 well, seismically basinward of ina, Caudammina, Saccammina, Dorothia, Trocham- 35r3±4, the middle to late Albian reservoir sands minoides and Lituotuba. and interbedded shales also have a rich and diversi- In Fig. 12, it may be seen that from 3587 to 3507 fied ABF assemblage. From 35r3±4 to 35r3±2 m, upper middle to lower upper Albian, the aggluti- calcareous benthics all but disappear, diversity of nated benthic foraminiferal assemblage is of high ABF increases, their test size decreases, and an diversity, with a diversity that increases upwards. It increase takes place in the frequency of Falso- differs from the agglutinated assemblages in the gaudryinellla, RecurÕoides, Reophax, Plectorecur- Polish Carpathians, that fewer PlectorecurÕoides and Õoides, Gaudryina and Saccamina. There is no obvi- PseudoboliÕina are present. There are no calcareous ous hydrodynamic sorting in the samples studied 82 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 from 35r3±2. The change in test size from larger in or disk-shaped forms, including Psammosphaera, 35r3±4 to smaller in 35r3±2, in conjunction with a Bathysiphon, Ammodiscus, and sideritic and pyritic higher diversity is interpreted as reflecting more concretions that maybe tiny burrows. The environ- optimal conditions for the flysch-type assemblage, as ment of deposition probably was largely dysaerobic, found in lower energy, deeper marine, more distal semi-restricted, and of high energy due to turbidite conditions. This agrees with the more distal basin scouring, and on average unfavourable to a diversi- setting from seismic interpretationŽ B. Torudbakken, fied benthic life. A bathyal setting is most likely, in pers. comm., 1995. . agreement with the fairly common presence of tubu- The conclusion from the paleoecologic interpreta- lar agglutinated taxa, like Bathysiphon. In discussion tion is that the Agat reservoir sands in 35r3±4 were with W. Kuhnt and T. SñtherŽ. pers. comm., 1996 , laid down in an upper bathyal, dysaerobic environ- the possibility was raised that such a benthic ment, that slightly shallowed upward, and became foraminiferal assemblage might represent overbank better oxygenated across the Albian±Cenomanian deposits at bathyal depth, to the side of a mass-flow boundary interval. sand conduit. Where sands were sampled, presumably in these conduits, no foraminiferal assemblage 7.3. Lysing formation, upper Cenomanian±Turonian was recovered, also not shallow marine taxa that could be considered transported down slope. A poorly understood assemblage of agglutinated Another scenario is that the common Psammo- foraminifers occurs in Cenomanian, and particularly sphaera component, found as dominant form in many in Turonian sand-prone mudstone strata, offshore Lysing samples in the region, was an early seafloor mid Norway, north of the Agat area discussed above. colonizer after a mas-mortality event, reflecting a The interval includes gravity flow sands assigned to disturbed environment, due to repeated sand scour in the brittonensis and Dicarinella zones and part of a `fan sand delta'. A low oxygen watermass imping- the Marginotruncana zones, middle-late Cenoma- ing on the slope would keep benthic diversity low, nian and Turonian or slightly younger. The unit may further threatened by repeated erosional events from be over 1000 m thick, and is relatively poor in sand scour. Such an environment would favour microfossils. Sparse planktonic foraminifers indicate Psammosphaera as an opportunistic, early seafloor normal salinity,Ž. fairly open marine conditions; the settler, in a bathyal environment. poor benthic assemblage with few calcareous taxa Ž.Dentalina, Gyroidinoides, Pleurostomella , and few 7.4. Middle and upper Cretaceous breaks in the coarse agglutinated ones like Bathysiphon, Psammo- fossil record sphaera, Trochammina and Ammodiscus might reflect restricted bottom conditions in a bathyal setting, As mentioned earlier, the scaled optimum se- with some hydrodynamic sorting of test shapes, dur- quence of Fig. 5Ž. left shows major breaks between ing sediment transport in deeper water. Small pillbox several successive zones, including between the una diatoms are common and pyritized, pyritized radio- and schloenbachi zones, delrioensis LCO and brit- larians occur rarely, but testify to normal marine tonensis zones, Marginotruncana and polonica salinity, and bathyal conditions. A high sedimenta- zones, bellii and dubia zones, and particularly be- tion rateŽ. see Section 8 , under restricted bottom tween dubia and szajnochae zones. In trying to conditions, together with some sorting, and diage- answer what the meaning is of these large breaks in netic loss of taxa due to dissolution, probably com- the RASC scaling solution, it is useful to consider bined to yield the `impoverished' microfossil assem- how RASC scaling of relative interevent distances blage. The reason for a barren interval with the CrT operates. The relative distance between events in the boundary gamma spike, was touched upon under the optimum sequence is calculated from the frequency Dicarinella zone. of cross-over of all possible direct and indirect pairs Of interest is that several levels in wells, poor in of events in the optimum sequence. Hence, large microfossils, give the impression being sorted hydro- distances between successive events in the scaled dynamically, with a prevalence of spherical, tubular optimum sequence reflect strongly diminished re- F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 83 gional cross-over between the majority of events more condensed and more marly. Again, just as below and above the breaks. Reasons for these re- below the previous break, there is a LCO event just gional breaks must be thought in stratigraphic gaps below this RASC zonal break, in this case the and paleoenvironmental changes, related to sequence widespread Heterosphaeridium difficile LCO event, stratigraphic breaks, and will be discussed below. which may represents maximum transgressive flood- The una±schloenbachi break reflects a latest Al- ing, prior to the turn-around point in the eustatic bian lithofacies change, and hiatus. An uppermost sealevel cycle. Albian hiatus, assigned in some of the wells, may The significance of the bellii±dubia break in the truncate part or all of this zone, possibly related to RASC zonation is not obvious to us, but it may be the pronounced eustatic offlap cited by Hardenbol et significant that again a widely recognized LCO event, al.Ž. 1993; in press , and by Rohl and Ogg Ž. 1996 , at this time of Trithyrodinium suspectum isŽ. near or at the base of the Tethyan Mortoniceras inflatum zone. the RASC zonal break. Hence, a maximum flooding The hiatus is visualized by the large interfossil dis- horizon occurs likely at this level in the lower part of tance below A. grande, at the base of the RASC the Campanian; it approximates the transition from interval zone in Fig. 5Ž. left . In boreal NW Europe the early Campanian biosiliceous assemblage to the this level frequently is a disconformity, separating coarse agglutinated deep water foraminifer assem- upper Albian depositsŽ. not uppermost of the Stolc- blage in the North Atlantic and Tethys, discussed skaia dispar ammonite zone from the lowermost earlierŽ see Fenestrella bellii and Tritaxia dubia Cenomanian transgressive deposits of the lower N. zones. . carcitanense ammonite subzone The combined se- The dubia±szajnochae break reflects the abrupt quence boundary and transgressive surface is known change from siliciclasts to marly sediment at the as the Octeville transgressive surface in Normandy Campanian±Maastrichtian boundary, only noted in Ž.Hardenbol et al., in press . the southern part of the region. The delrioensis LCO±brittonensis break reflects In detail, individual well sedimentology and the mid-Cenomanian lithofacies change, and hiatus. stratigraphy may show more complexity than out- The hiatus is visualized by the large interfossil dis- lined here, but such will need local well log, lithol- tance in Fig. 5Ž. left below Batioladinium jaegeri,at ogy and possibly seismic input, and is beyond the the base of the brittonensis interval zone. The top of scope of this study that represents a first pass at the the zone extends above the sands of the Lange data. Formation, offshore mid-Norway, and is below or in sand of the basal Lysing Formation. Since recognition of the zone is dependent on suitable, shaly 8. Subsidence and sand sedimentation lithologyŽ the widespread gravity flow sands not being fossiliferous. , the full stratigraphic extent of Although speculative, we postulate that the the hiatus remains to be determined. The break widespread Barremian±Aptian disconformityŽ Fig. probably incorporates a maximum flooding horizon 2. may be linked to Atlantic rift-onset unconformi- with Hedbergella delrioensis LCO near the turn- ties, e.g., recognized offshore eastern Canada, north around position in the eustatic sealevel cycle, in late of the Figueiro Fracture zone and Newfoundland early Cenomanian. This level is than truncated by the Seamounts, prior to oceanisation just after M0 time mid-Cenomanian non-sequence, like the Rouen hard- Ž.Jansa and Wade, 1975 . As argued above, ongoing ground of northern FranceŽ Hardenbol et al., 1993; in block-faulting, coupled to weak thermal subsidence, press. . and first order global sea level rise, increased water The considerable Marginotruncana-polonica depth in Aptian±Albian time from neritic to upper break at the level of H. difficile may reflect the bathyal, and created sedimentary clastics accommo- lowstand between two major tectono-eustatic cycles dation space, in a dysaerobic, restricted setting. Just in middle ConiacianŽ. Hardenbol et al., in press . above the Albian±Cenomanian boundary, watermass There is no doubt that above the break, at the end of conditions in the SW part of the study regionŽ e.g., Lysing sand deposition time, the section is generally Agat region. changed from dysaerobic to normal 84 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Fig. 15. Schematic illustration of Cretaceous chronostratigraphy and gravity flow sand pulses in the seaway between Norway and Greenland; slightly modified after Dore et al.Ž. 1997 . For details, see text. oxygenated marineŽ. Fig. 12 , the cause of which on a westward prograding, slope to basin apron must lie in more widespread palaeoceanographic and Ž.Saether et al., 1997 . As we have discussed earlier, tectonic changes, as discussed earlier. turbidity currents are not uncommon, and agree with The Cenomanian±Turonian sand facies geneti- an upper bathyal, flysch-type agglutinated forami- cally are grouped as gravity flows, which operated niferal assemblage that is locally hydrodynamically

Fig. 16. Airy compensated tectonic subsidence and uplift plot for well 6406r2±2Ž. bargraph in lower part of figure , and the decompacted burial curves for 6406r2±2, and well 35r3±4Ž. respectively middle and upper part of this figure . The two wells are several hundred km apart. Four successive stages of tectonic subsidence and subsequent sedimentation clearly stand out. The first stage operated from 200 to 160 Ma, Jurassic, and may be conventionally described as an early to middle Jurassic rifting event followed by thermal relaxation and some sediment loading. The second tectonic stage operated in middle Cretaceous, 100±80 Ma, and may have been enhanced by subsequent sediment loading. The third tectonic stage was active around 60 Ma, related to the opening of the Norwegian sea, while the fourth tectonic stage operated in the late Neogene, and may be ongoing today. Comparable subsidence and burial patterns are also seen in many other wells throughout the region under study, between 608 and 678 N. The combination of a brief hiatus plus shallowing in the uppermost Albian appears as a rapid uplift, which might be expected regionally, just prior to Lower Cenomanian sand deposition. A tenfold increase in subsidence and sedimentation took place in Cenomanian through Coniacian time, during about 15 m.y., creating considerable deep marine sand deposition potential. F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 85 86 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 sorted. In Fig. 15, which is slightly modified after Albian in the 35r3±4 well discussed earlier. Subsi- Dore et al.Ž. 1997 , these authors have tried to sum- dence modelling of the observed mid-Cretaceous marize the spatial and chronostratigraphic distribu- burial trends with local airy isostatic compensation tion of conjugate sand units, off east Greenland and Ž.lower part of Fig. 16 , leaves no doubt the mid- off western Norway. The figure, albeit sketchy, Cretaceous trend is tectonic. The tenfold increase in clearly shows the Albian±middle Campanian distri- subsidence and sedimentation raised sand deposition bution of reservoir sand targets in exploration, off- potential. Reasons for this dramatic increase in sedi- shore Norway. ment accommodation potential, offshore Norway are The question if local block faulting generated not well understood, but tentatively are linked to local or widespread uplift for sand erosion, and basinal extension and basin margin uplifts during simultaneously increased accommodation space in mid-Cretaceous plate-tectonic re-organisation. For the basins to deposit the sands, is an interesting one example, one scenario links such uplifts and surge in that may be looked upon in a geodynamic context. sedimentation are due to an `intra-Cenomanian' tec- Take for example the airy compensated tectonic tonic event. This event could be related to the fact subsidence and uplift plot for well 6406r2±2Ž lower that in mid-Cretaceous time, a significant change in part of Fig. 16. , and the decompacted burial curves stretch was modelled in the Rockal area from SW± for that well, and for well 35r3±4, in the upper part NE to SE±NW. Prior to Cenomanian, conjugate of Fig. 16, southwesternŽ. Agat area. The two wells Grand BanksrIberiaŽ south of the Charlie Gibbs are several hundred km apart. Four successive stages fracture zone. underwent transition to drifting, of tectonic subsidence and subsequent sedimentation whereas north of this fracture zone, between stand out clearly. The first one operated from 200 to LabradorrGreenland and between GreenlandrNW 160 Ma, Jurassic, and may be conventionally de- Europe, this drifting is post-Cenomanian in age. scribed as a Early to Middle Jurassic rifting event This relatively briefŽ. less than 20 m.y. tectonic followed by thermal relaxation, and sediment loading episode, known widespread offshore Norway, and of basement. The second tectonic stage operated in not only in the two wells shown makes the mid- mid-Cretaceous, 100±80 Ma, and may have been Cretaceous attractive in the search for stratigraphic enhanced by subsequent sediment loading, the third traps. It is striking that the stratigraphic distribution one around 60 Ma is related to the opening of the of the Norwegian deep marine sand targets in Fig. Norwegian sea, while the fourth one operated in the 15, from Albian through middle Campanian, almost late Neogene and may be ongoing today. From the exactly coincide with the 105 through 75 Ma, Albian literature it is not known if detailed geodynamic through middle Campanian high burial rate in the modelling has been performed on the second and mid-Norway well of Fig. 16. Although it is quite fourth tectonic episodes. possible that on a local scale sequence stratigraphic What may be surmised from the mid-Cretaceous episodes played a role in the sand distributionŽ cf. tectonics? After a modest increase of burial rate in Dore et al., 1997. , the overall control on the sand the Albian, Cenomanian±Turonian time sedimenta- deposition potential is related to the still enigmatic tion rates increased 10-fold, but paleo waterdepth did mid-Cretaceous tectonic phase. not deepen noticeably, as shown in decompacted A widespread upper Maastrichtian±Danian hiatus, burial curves. Enough sediment `rushed forward to accompanied by some upliftŽ. Figs. 2 and 15 , reflects fill the hole', at least in the study area, but more `break-up', prior to the onset of Paleogene seafloor distal parts of the seaway may have subsided to spreading in the Norwegian Sea. This plate tectonic middle bathyal paleo waterdepths. driven opening changed the Cretaceous epicontinen- The combination of a brief hiatus plus shallowing tal, bathyal seaway into an abyssal oceanic basin. in the uppermost Albian, appears in the models of Fig. 16 as a rapid uplift, which can be expected 9. Conclusions regionally, just prior to lower Cenomanian sand deposition in aŽ. suddenly rapidly subsiding basin. This The narrow seaway between Greenland and Nor- is in line with shallowing observed in the uppermost way, in Cretaceous time was over 1500 km long and F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 87

300q km wide, and partly of bathyal water depth tion served as a template to build a Cretaceous zonal during Aptian through Campanian. It received a model with 19 assemblage and interval zones. The large volume of fine-grained siliciclastic sediments, zones are: with intercalated, gravity-flow sandstone wedges. As Protomarsonella kummi zone, early to middle a conduit for heat transport between the low latitudes Hauterivian; and polar region, Atlantic watermasses particularly Falsogaudryinella praemoesiana zone, late Hau- affected the eastern, Norwegian margin of this sea- terivian±earliest Barremian; way. Despite its high-latitude setting, calcareous and Falsogaudryinella xenogena zone, early Bar- few siliceous planktonic microfossils thus play an remian; important role in regional stratigraphy and facies GaÕelinella barremiana zone, Barremian; analysis, and a majority of fossil events correlate to Verneuilinoides chapmani zone, late Aptian±early NW European basins. Cosmopolitan, agglutinated Albian; deep water foraminifers also are widespread, and RecurÕoidesrGlomospira zone, middle Albian; assist with the biozonation. An agglutinated UÕigerinammina una zone, late middle to early foraminiferal bloom occurs in Campanian time, relate Albian; lated to a similar bloom in the Atlantic Ocean. Many Osangularia schloenbachi zone, late Albian; Cretaceous fossil events can be correlated to the Sigmoilina antiqua zone, early Cenomanian; Atlantic and west Tethys regions. Three new micro- Hedbergella delrioensis LCO zone, late early fossil taxa include UÕigerinammina una, Ammoanita Cenomanian±early middle Cenomanian; globorotaliaeformis, and Fenestrella bellii. Whiteinella brittonensis zone, late middle to early The eastern margin sedimentary succession may late Cenomanian; be subdivided in several broad lithologic units;Ž. 1 Dicarinella zone, latest Cenomanian±middle Tur- Thin, multicoloured, marly sediments of Hauteriv- onian; ian±Barremian age, with a shallow marine Falso- Marginotruncana zone, late Turonian±Coniacian; gaudryinellarnodosariidrostracod assemblage;Ž. 2 Stensioeina polonica zone, early to middle Santo- Dark mudstones and minor sands, Aptian-early nian; Cenomanian in age, with an upper bathyal, aggluti- Inoceramus LCO zone, late Santonian; nated assemblage, and monotypic Hedbergella Fenestrella bellii zone, early Campanian; floods;Ž. 3 Thick mudstone facies with thin, slope- Tritaxia dubia zone, middle to late Campanian; apron turbidite sands, and an impoverished benthicr Reussella szajnochae zone, early Maastrichtian; planktonic assemblage of late Cenomanian±Conia- Pseudotextularia elegans zone, late Maastrichtian. cian age, deposited in an upper bathyal, oxicrdys- Planktonic flood events occur in late Albian aerobic environment. Where Turonian sedimentation through early Cenomanian, early±mid Turonian, late rates are low, a planktonic foraminiferal assemblage Santonian±earliest Campanian and mid-Maastrich- with Whiteinella, Hedbergella, Dicarinella, and tian, the result of northwards shifts of warmer water Marginotruncana occurs;Ž. 4 Grayish, laminated masses, and disruptions in water stratification in the mudstones, Santonian±Campanian in age, with local dysaerobic basins. sands in the north, a low diversity, middle to upper The combination of deterministic and probabilis- bathyal benthicrplanktonic foraminiferal assem- tic biostratigraphic models enhances reproducibility blage, and an Inoceramus prisms and radio- of the results, and brings out stratigraphically impor- larianrdiatom flood; a Campanian agglutinated tant properties of the data, not otherwise accessible, foraminiferal bloom also is known from the Atlantic including estimates from variance analysis on the oceanic realm;Ž. 5 More marly sediments of Maas- reliability of correlation for 72 of the zonal events. trichtian age, with a low diversity planktonicrben- Using variance analysis, four groups of events stand thic foraminiferal assemblage. out. Using the distribution of 1755 foraminiferal and Firstly, there are calcareous planktonic LO and dinoflagellate microfossil events in over 30 explo- LCO events that reflect oxic watermass conditions, ration wells, a RASCŽ. Ranking and Scaling zona- relatively high fertility and slow sedimentation. These 88 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 events include Rugoglobigerina rugosa and Glo- near the Santonian±Campanian boundary, suggesting bigerinelloides Õolutus, red coloured planktonics, In- that it is a useful regional stratigraphic marker, off- oceramus needles LCO, Dicarinella imbricata, and shore Norway, particularly if sediments would be Hedbergella delrioensis LCO. All of these events cored. occur in many wellsŽ except `Red coloured plankton- A fourth category of events are dinoflagellate ics' that is confined to eight of the southern wells, cysts that are extensively used for mid-Cretaceous and D. imbricata), have low standard deviations in well stratigraphy, but are of variable stratigraphic correlation, and histograms of stratigraphic devia- quality. These events include Trithyrodinium suspec- tions that are relatively normal in shape. The same tum LCO, Heterosphaeridium difficile LCO, Endo- holds for the benthic foraminiferal events Reussella ceratium dettmaniae, Litosphaeridium siphonipho- szajnochae and Stensioeina polonica. Hence, these rum, M. membraniphorum, Epelidosphaeridia commonly observed, oxic watermass events are con- spinosa, OÕoidinium scabrosum and Apteodinium sidered reliable zone markers. grande. The events have low S.D. values and normal Secondly, there are agglutinated benthic events frequency distributions, except for E. dettmaniae, L. that reflect dysaerobic watermass conditions, and siphoniphorum, M. membraniphorum, and E. fine grained, low carbonate, mudstone substrate. spinosa. The latter four events have high S.D. val- These events are Tritaxia dubia, Coarse Aggluti- ues, and not normal histograms of stratigraphic devi- natedŽ. Deep Water Foraminifers LCO, and UÕigeri- ations, indicative of low value as zonal markers. A nammina una, with low standard deviations, and factor, other than common reworking of these four histograms of stratigraphic deviations, which indicate events in the often sandy Cenomanian interval that their value as zone markers. The Campanian Coarse makes it difficult to pick them in wells, is that the Agglutinated LCO event generally is easy to recog- LO's of L. siphoniphorum and E. spinosa maybe nize in wells. It may be slightly time-transgressive, time transgressive, ranging younger southward. but stratigraphic resolution is limited in the upper The quantitative zonation Žsscaled optimum se- part of Campanian. quence. shows major breaks between several succes- Thirdly, there are siliceous planktonic events that sive zones, including between the una and schloen- reflect high watermass fertility. These events are bachi zones, delrioensis LCO and brittonensis Fenestrella bellii n. sp. and sphericalrlenticular ra- zones, Marginotruncana and polonica zones, bellii diolarians, with fairly low standard deviations. The and dubia zones, and particularly between dubia histograms of stratigraphic deviations are normal, and szajnochae zones. We postulate the following which suggests that the events are coeval over the reasons for the stratigraphic breaks between zones. many wells where they are observed. The radiolarian Ž.1 The una±schloenbachi break reflects a latest bloom event may be difficult to recognize in wells, Albian lithofacies change and hiatus, connected to since scattered radiolarians occur also in stratigraphi- the Octeville hiatus in NW Europe. cally younger levels that may be mistaken for this Ž.2 The delrioensis LCO±brittonensis break re- event. Differences in sedimentation rates between flects the mid-Cenomanian lithofacies change and wells also tend to obscure the event. In the North hiatus, connected to the mid-Cenomanian non-se- Atlantic, greenish radiolarian-rich sediments appear quence, and Rouen hardground.

Plate III. Fenestrella bellii Gradstein and Kaminski, n.sp. Figs. 1±3, well 6507r6±2, Fenestrella bellii zone, cts. 2320 m, offshore mid-Norway; holotype in Fig. 1. Specimens were pyritized during burial. UÕigerinammina una Gradstein and Kaminski, n.sp. Fig. 4a,b Ž.holotype , UÕigerinammina una zone, well 6507r6±2 at cts. 3110 m, offshore mid-Norway. The specimen in Fig. 5 is from cts. 3040 m in the same well. AmmoanitaŽ. Trochammina globorotaliaeformis Gradstein and Kaminski, n.sp. Figs. 6±8 Ž same specimen, holotype . UÕigerinammina una zone, well 6507r6±2 at cts. 3110 m, offshore mid-Norway. F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 89 90 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Ž.3 The Marginotruncana±polonica break, above Acknowledgements the level of Heterosphaeridium difficile LCO, which represents a maximum flooding surface, may be the This manuscript grew out several invited presenta- turn-around in the middle Coniacian tectono-eustatic tions in Norway and abroad onŽ. bio stratigraphy and phase, near the end of the Lysing sand deposition paleoceanography of the Cretaceous seaway between phase. Norway and Greenland. It was written in honour of Ž.3 The bellii±dubia break, significantly is again the 75th birthday of Prof. C.W.Ž. Cor Drooger, Ž.near or at a maximum flooding event, this time Utrecht University, who with his staff, vigorously correlated to the LCO of T. suspectum in the early taught stratigraphy, and stimulated more objective, middle Campanian, above the change from marly quantitative approaches in micropaleontology. We sediments to siliciclastic sediments at the base of the thank the Geological Survey of Canada and Saga Campanian. Petroleum for support with continued development Ž.4 The dubia±szajnochae break reflects the of the quantitative stratigraphic methods, and Quim- abrupt change from siliciclastic to marly sediment at ing Cheng for creative graphics programming. the Campanian±Maastrichtian boundary, noted in the This study benefitted from pleasant cooperation, southern part of the region. manuscript review, andror discussions with many A widespread earliest Cretaceous hiatus separates colleagues, of which we particularly like to mention Jurassic from Cretaceous strata. Ongoing block-fault- Tormod Saether and Joerg Mutterlose. The authors ing, coupled to thermal subsidence and global alone are responsible for the scientific opinions ex- sealevel rise increased water depth in Aptian±Albian pressed in this study. time from neritic to bathyal, and created sand accommodation space in dysaerobic, restricted settings. In Cenomanian±Coniacian time, sedimentation rates in the `central basin' increased 10-fold, whereas paleo waterdepth did not deepen. This relatively briefŽ less than 10 Ma. tectonic episode, resulting in deposition Appendix A of deep water sands, is tentatively linked to stress re-orientation in the Rockall area. A widespread Catalogue of approximately 250 foraminiferal upper Maastrichtian±Danian hiatus, the result of taxa, and some miscellaneous forms, observed by us `shoulder' uplift, reflects `break-up', prior to the in the Cretaceous, offshore mid Norway. The taxa onset of Paleogene seafloor spreading in the Norwe- have been grouped in four broad time slices that gian Sea. This plate tectonic driven opening changed reflect broad evolutionary turnover, and biofacies the Cretaceous epicontinental, bathyal seaway into development, offshore Norway. Relative abundance: an abyssal oceanic basin. rÐrare, xÐcommon, oÐfrequent, ooÐabundant.

Agglutinated Benthics Raresr Frequentso Calcareous Benthics Raresr Frequentso Commonsx Abundantsoo Commonsx Abundantsoo HAUTERIVIAN±BARREMIAN Rhizammina sp. r Globospirillina neocomiana xo Saccammina compressa r Spirillina spp. x Ammodiscus spp. x o Patellina subcretacea x Reophax spp. x Trocholina infracretacea r Pseudonodosinella troyeri x Lagena hauteriÕiana x Glomospira charoidesr xo Lingulina semiornata r gordialis F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 91

Agglutinated Benthics Raresr Frequentso Calcareous Benthics Raresr Frequentso Commonsx Abundantsoo Commonsx Abundantsoo HAUTERIVIAN±BARREMIAN Glomospirella gaultina x Pseudonodosaria sp. r Haplophragmium aequale x Citharina harpa r Bulbobaculites sp. x Saracenaria spp. r Ammobaculoides carpathicus r Lenticulina munsteri oo Haplophragmoides sp. x o L. aff. subalata r Cribrostomoides nonioninoides x L. heiermanni r RecurÕoides spp. x L. guttata r Protomarsonella kummi x L. ouachensis wisselmanni r Trochammina spp. x I. aff. nodosa r Textularia bettenstaedti x L. saxonica r Falsogaudryina xenogena xo L. cf. busnardoi r F. praemoesiana x Planularia crepidularis r F. tealbyensis r Marginulina bettenstaedti r Verneuilinoides neocomiensis x GaÕelinella sigmoicostata r GaÕelinella barremiana x Conorboides lamplughi r Epistomina tenuicostata r E. hechti r Miscellaneous E. ornata r Small planktonic foraminifera x E. chapmani r Ž.sBlefuscuiana E. caracolla x OstracodaŽ. mostly smooth x o Conorotalites bartensteini r

APTIAN±ALBIAN Rhizammina sp. x o Lenticulina spp.Ž. smooth x Rhabdammina spp. x o Pleurostomella barroisi r Kalamopsis grzybowskii r GaÕelinella intermedia x Hippocrepina depressa r GaÕelinella sp. x Psammosphaera spp. x o Osangularia schloenbachi x Ammodiscus spp. x o Epistomina spinulifera gr. r Caudammina crassa r Gyroidinoides x infracretaceus Reophax spp. x o G. sp. r Pseudonodosinella troyeri r Polymorphinidae r Glomospira charoidesr xoo Dentalina sp. r gordialis Glomospirella gaultina xo Sigmoilina antiqua x Cribrostomoides nonioninoides x ValÕulineria gracillima x Haplophragmoides spp. x o Eponides sp. r H. kirki r H. minor x H. concaÕus x Ammosphaeroidina sp. r Planktonic Foraminifera Ammoanita globorotaliaeformis xo Hedbergella infracretacea o n.sp. Trochammina sp. r Hedbergella planispira oo T. abrupta r H. delrioensis xo T. quinqueloba r Globigerinelloides x bentonensis 92 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Agglutinated Benthics Raresr Frequentso Calcareous Benthics Raresr Frequentso Commonsx Abundantsoo Commonsx Abundantsoo APTIAN±ALBIAN RecurÕoides spp. x o PlectorecurÕoides irregularis r P. alternans r Thalmannammina neocomiensis r Miscellaneous PseuboliÕina Õariabilis r pyritized radiolarians r UÕigerinammina una n.sp. x o Inoceramus needles x Ž.pink, white Falsogaudryinella alta xo Textularia foeda r T. bettenstaedti r Gaudryina filiformis r Verneuilinoides chapmani x Arenobulimina sp. r ClaÕulina gaultina r

CENOMANIAN±TURONIAN Rhizammina sp. x o Allomorphina pyriformis x Rhabdammina spp. x oo A. halli r Psammosphaera spp. x oo Pleurostomella obtusa r Ammodiscus tenuissimus xoo Lenticulina spp.Ž. smooth r Reophax spp. x o GaÕelinella intermedia x Caudammina oÕulum r G. sp. XŽ. unpublished x C. oÕuloides r G. sp. r Glomospira charoidesr xo GaÕelinopsis cenomanica r gordialis Glomospirella gaultina x LingulogaÕelinella r jarzeÕae Bulbobaculites problematicus r Globorotalites spp. r Arenoturrispirillina sp. r Gyroidinoides nitida x Haplophragmoides spp. x o ValÕulineria gracillima x RecurÕoides imperfectus r Stensioeina humilis r Trochammina spp. x o Rzehakina spp. r Ž.including R. minima Psamminopelta sp. r Planktonic Foraminifera PlectorecurÕoides alternans r Globigerinelloides x bentonensis Thalmanammina neocomiensis r Hedbergella delrioensis xoo PseudoboliÕina sp. r H. planispira xo UÕigerinammina() pre- jankoi r H. paradubia x Gerochammina spp. x H. hoelzi x Gaudyrina filiformis x H. sigali r Eggerinella mariei r ClaÕihedbergella simplex r Ammosphaeroidina sp. r Whiteinella brittonensis x Dorothia spp. x W. inornata r Textularia foeda r Praeglobotruncana x stephani T. sp. 1 B and B81 r P. delrioensis x F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 93

Agglutinated Benthics Raresr Frequentso Calcareous Benthics Raresr Frequentso Commonsx Abundantsoo Commonsx Abundantsoo CENOMANIAN±TURONIAN T. chapmani r P. praehelÕetica r T. pyramidata r Dicarinella hagni indica x Pseudotextularia cretosa r D. inbricata x Marsonella ozawaiqspp. r D. primitiÕa x Spiroplectammina cf. carinata r Marginotruncana xo marginata Arenobulimina adÕena r Globotruncana linnneiana gr. r Heterohelix globulosa r

CONIACIAN± MAASTRICHTIAN Rhizammina sp. x o Eponides beisseli x Rhabdammina spp. x oo GaÕelinella sp. r Psammosphaera spp. x oo Pullenia sp. x Ammodiscus spp. x oo GaÕelinella usakensis r A. bornemanni r G. beccariiformis x Reophax spp. x o Conorbina supracretacea x Caudammina oÕulum x Nuttalina florealis x C. oÕuloides r Globorotalites multiseptus x Glomospira charoidesr xo G. micheliniana r gordialis Rzehakina spp. r Stensioeina granulata r Ž.including minima polonica Psamminopelta bowsheri r S. pommerana r Haplophragmoides spp. x o Brizalina ex. gr. incrassata x H. walteri excaÕatus x Reussella szajnochae x H. aff. walteri sensu x Kuhnt and Kaminski RecurÕoides sp. r Planktonic Foraminifera Trochammina spp. x o Globotruncana arca r Paratrochamminoides x G. linneiana gr. x olszewska P. mitratus x G. fornicata x Trochamminoides x G. bulloides x subcoronatus T. spp. x G. mariei r Spiroplectammina dentata r Rosita Ž.Globotruncana r contusa S. naÕarroana r Rugoglobigerina rugosa xoo Gaudryina filiformis xo R. rotundata r Karrerulina conÕersa x G. Õolutus xoo Gerochammina spp. x Dicarinella concaÕata r Remesella Õarians D. carinata r Marsonella crassa Abathomphalus x mayaroensis Tritaxia dubia Globotruncanella r intermedia G. haÕanensis x 94 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Agglutinated Benthics Raresr Frequentso Calcareous Benthics Raresr Frequentso Commonsx Abundantsoo Commonsx Abundantsoo CONIACIAN± MAASTRICHTIAN Miscellaneous Pseudoguembelina excolata r Fenestrella bellii n.sp. oo Racemiguembelina Õarians r lenticularrspherical radiolarians oo Whiteinella archeocretacea x

Appendix B Dimensions: Specimens range between 150 and 300 micrometer in size. Genus: UÕigerinammina. Remarks: The nominate taxon, UÕigerinammina Species: UÕigerinammina una Gradstein and una, apparently is a boreal species restricted to the Kaminski, new species. Norwegian and North Sea regions. It appears not to Illustrations: Plate III, Fig. 4a,b, Fig. 5. possess calcareous cement, therefore it cannot be Synonymy: 1981ÐUÕigerinammina sp. 1 Burn- assigned to the genus Falsogaudryinella. Most likely hill and Ramsay. it belongs in the genus UÕigerinammina, as origi- Derivation of name: Latinisation of the original nally reported by Burnhill and RamsayŽ. 1981 . It has open nomenclature name UÕigerinammina sp. 1 not been found in the Albian of the Kirchrode-1 Burnhill and Ramsay, 1981. Borehole, NW GermanyŽ Jaroslaw Tyszka, personal Diagnosis: Test rounded triserial, rapidly expand- communication. , or in deep-sea deposits. The acme ing in width, with last whorl occupying most of test. of UÕigerinammina una itself often forms a narrow Holotype: Housed in the Micropaleontology Col- zone, but the species also is found in low numbers in lection of the British Museum of Natural History, both the immediately overlying and immediately un- London. derlying zones. Material, localities and horizons: The type level The species differs from co-occurring UÕigeri- is the interval of 3040±3130 m in greenish mud- nammina alta in its much wider test; U. alta is stones in well 6507r6±2, offshore mid Norway. The relatively long and slender. species is known from the UÕigerinammina una zone, late middle Albian to early late Albian. Auxil- iary material is in the UK North Sea well 21r1A±10 at 2765 m, assigned by Burnhill and RamsayŽ. 1981 Genus: Ammoanita. to upper Albian. Species: Ammoanita globorotaliaeformis Grad- Additional occurrences of this new taxon, off- stein and Kaminski new species. shore Norway are in wells 6507r2±1 at 3580 m, Illustrations: Plate III, Figs. 6±8. 6507r2±3 at 3450 m, 6506r12±5 at 3727.50 m, Derivation of name: Based on resemblance of 6406r2±2 at 4260 m, 6406r2±3 at 4578 m, the Ammoanita specimens to a high conical, many 6506r12±4 at 3784 m; 35r3±2 at 3639.10 m, chambered planktonic foraminifer of the genus 35r3±4 at 3542.10 m, 35r12±1 at 2310 m, 35r11±2 Globorotalia. at 2712 m, and 34r7±21 A at 2852 m. Diagnosis: Planoconical, high spired with nine or Description: Test triserially coiled, with three more chambers in last whorl; chambers strongly whorls, the last one of which occupies most of the overlap; sutures swing backward. test and widens rapidly; the greatest width of the Holotype: Housed in the Micropaleontology Col- semicircular test is halfway up the last whorl. Su- lection of the British Museum of Natural History, tures slightly depressed. Test smooth, shiny, fine London. The holotype is registered in slide PF 66923. grained agglutinated with organic cement. Aperture a Material, localities and horizons: The type level elongate opening, bordered by a rim, at the top of is the interval of 3040±3140 m in greenish mud- last chamber. stones in well 6507r6±2, offshore mid Norway. F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98 95

This interval belongs in the UÕigerinammina una During final stages of this study, we became zone, late middle Albian to early late Albian. The aware of a study by TairovŽ. 1961 , in which the species appears to be restricted to this zone. Addi- author described and illustrated several conical taxa tional occurrences of this new taxon, offshore Nor- of Trochammina from the Cretaceous of Adzerbay- way are in wells 6507r2±3 at 3450 m, 6406r2±2 at dzhan. Taxa include T. planuliformis and T. globoro- 4280 m, 35r3±5 at 3476 m, and 34r7±21A at taliforma. It is not clear at this stage if any types are 2852.22 m. preserved, andror available for study. Description: Test trochospirally coiled, with two to four whorls; spiral side flat; umbilical side highly Genus: Fenestrella. convex, with no or only a narrow umbilical depres- Species: Fenestrella bellii Gradstein and Kamin- sion; periphery acute. Outline circular to slightly ski, new species. lobate. Chambers are numerous, increasing rapidly in Illustrations: Plate III, Figs. 1±3. height, nine or more in the last whorl; last chamber Synonymies: Unpublished well completion re- may tower over previous ones. Sutures limbate, and ports for the offshore Norway area report this taxon can be slightly depressed or smooth; on the umbilical either as Diatom sp. H. Stratlab, or as Diatom sp. 17 side the sutures are curved backward; on the spiral Robertson Research. side the sutures are tangentially situated. Wall agglu- Derivation of name: Named after Dr. Graham tinated, silicified. Aperture extraumbilical, poorly Bell, Stratlab, Norway in recognition of his detailed visible, a slit at the base of the final chamber. well research with stratigraphic palynology, offshore Dimensions: Specimens range between 125 and Norway. 300 micrometer in diameter. Diagnosis: A small and pyritized diatom test that Remarks: We place this species in the genus is disk shaped with sharp periphery. Ammoanita Seiglie and Baker, rather than in Holotype: Housed in the Micropaleontology Col- Trochammina because of its angular chambers and lection of the Department of Botany of the British acute periphery. According to our observations Am- Museum of Natural History, London. The holotype moanita globorotaliaeformis has a tighter coil than is registered in slide BM 100179. the Paleocene A. ingerlisae Gradstein and Kaminski, Material, localities and horizons: The type level with chambers increasing more rapidly in height, and is in mudstones at 2320 m in well 6507r6±2. Addi- more chambers in the last whorl. In local well com- tional types are from 2330 m in well 34r7±7, also pletion reports such specimens are referred to as offshore Norway. The type level is the Fenestrella Trochammina globorotaliaformis, and constitute a bellii zone, lower Campanian. Additional occur- useful mid±upper Albian index. rences of this taxon, widespread and common off- Charnock and JonesŽ. 1990 mention occasional shore Norway are in wells 6610r3±1 at 2245 m, specimens of their Trochammina subÕesicularis in 6607r5±2 at 4134 m, 6607r5±1 at 3172 m, Albian mudstones, offshore mid Norway, which 6507r2±2 at 2220 m, 6507r2±3 at 2400 m, probably belong in the new taxon Ammoanita 6507r7±1 at 2330 m, 6507r7±2 at 2091 m, globorotaliaeformis. 6506r12±4 at 2449 m, 6406r2±1 at 2700 m, and Trochammina abrupta Geroch of the middle Cre- 34r7±24 s at 2630 m. taceous Verovice Beds of Poland is less planocon- Description: Test small, always pyritizedŽ due to vex, has more radial sutures, far fewer and wider depth of burial below the stability level of siliceous chambers and a wider spire than A. globorotaliae- tests. and shiny. The tests are disk shaped, with a formis. circular equatorial outline, a rather sharp periphery, T. subÕesicularis Hanzlikova, of the Albian of and a low conical side view, giving rise to the Czechoslovakia has fewer chambers in the last whorl distinctive oval or low-conical cross-section when and is more strongly planoconvex, with a lobate viewed perpendicular to the equatorial plane. Some periphery. Its chambers increase more rapidly in specimens show a small dimple in the cone. height than A. globorotaliaeformis Žsee Gradstein Dimensions: Specimens range between 80 and and Kaminski, 1997. . 150 micrometer in diameter. 96 F.M. Gradstein et al.rEarth-Science ReÕiews 46() 1999 27±98

Remarks: This species also occurs stratigraphi- Charnock, M.A., Jones, R.W., 1990. Agglutinated foraminifera cally in lower zones than the F. bellii zone. Its total from the Palaeogene of the North Sea. In: Hemleben et al., Ž. stratigraphic range has not been determined, but it Eds. , Paleoecology, Biostratigraphy, Paleoceanography and Taxonomy of Agglutinated Foraminifera, Nato ASI Series, C. may range down from the F. bellii zone into the 327, Kluwer Academy Publ., pp. 139±244. Marginotruncana zone. The last occurrence and last Coccioni, R., Galeotti, S., Gravili, M., 1995. Latest Albian±earliest common occurrence are stratigraphically distinct and Turonian deep-water agglutinated foraminifera in the Botta- key indicators for the F. bellii zone, assigned to cione sectionŽ. Gubbio, Italy Ðbiostratigraphic and palaeoeco- lower Campanian. logic implications. Rev. Espanola Paleont., 135±152. Costa, L.I., Davey, R.J., 1992. Dinoflagellate Cysts of the Creta- ceous System. 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Erratum Erratum to: Biostratigraphy and paleoceanography of the Cretaceous seaway between Norway and Greenland wEarth-Science Reviews 46ž/ 1999 27±98xq

F.M. Gradstein a,), M.A. Kaminski b, F.P. Agterberg c a Saga Petroleum ASA, KjorboÕeien 16, P.O. Box 490, N-1302 SandÕika, Norway b KLFR, 3 Boyne AÕenue, Kendon, NW4 2JL, UK c Geological SurÕey of Canada, Ottawa, Ontario, Canada

In the original article a previous version of Plate 3 has been printed. The correct version is given here. The publisher apologizes for any inconvenience caused.

q PII of original article S0012-8252Ž. 99 00018-5 ) Corresponding author. Tel.: q47-67-126-141; fax: q47-67-126-585. E-mail address: [email protected]Ž. F.M. Gradstein .

Plate 3. Fenestrella bellii Gradstein and Kaminski, n.sp. Figs. 1±3, well 6507r6-2, Fenestrella bellii zone, cts. 2320 m, offshore mid-Norway; holotype in Fig. 1. Specimens were pyritized during burial. UÕigerinammina una Gradstein and Kaminski, n.sp. Fig. 4a,b Ž.holotype , UÕigerinammina una zone, well 6507r6-2 at cts. 3110 m, offshore mid-Norway. The specimen in Fig. 5 is from cts. 3040 m in the same well. AmmoanitaŽ. Trochammina globorotaliaeformis Gradstein and Kaminski, n.sp. Figs. 6±8 Ž same specimen, holotype . UÕigerinammina una zone, well 6507r6-2 at cts. 3110 m, offshore mid-Norway.