Biostratigraphy of a Lower Cretaceous section from Sklinnabanken, Norway, with some comments on the Andøya exposure
NILS AARHUS, JACOB VERDENIUS & TOVE BIRKELUND
Aarhus, N., Verdenius, J. & Birkelund, T.: Biostratigraphy of a Lower Cretaceous section from Sklinnabanken, Norway, with some comments on the Andøya exposure. Norsk Geologisk Tidsskrift, Vol. 66, pp. 17-43. Oslo 1986. ISSN 0029-196X.
Ryazanian black shales in a core dose to the eastern margin of the Trøndelag Platform offshore Hel geland, northern Norway are overlain by a condensed latest Ryazanian-Barremian sequence of grey and red Utvik Formation equivalent marls and mudstones. Palaeontological studies show that the 'Late Cimmerian Unconformity' represents only a minor hiatus in the Upper Ryazanian. Upper Val anginian-Lower Hauterivian beds seem to be absent. The generalized model for the North Sea and adjacent areas (Rawson & Riley 1982) thus seems applicable to more northern areas, as would be ex pected if sedimentation was mainly controlled by eustatic sea level changes. The section is compared to the Lower Cretaceous sequence at Andøya, the stratigraphy of which is revised.
N. Aarhus & J. Verdenius, Inst. for kontinentalsokkelundersøkelser og petroleumsteknologi AlS, Post boks I883, 7001 Trondheim, Norway. T. Birkelund, Inst. for hist. geo/. og palæont., Københavns Universitet, Øster Voldgade JO, DK-1350, København K, Denmark.
The major break interpreted from seismic pro Wire line coring with 100% recovery started at files and lithology at the base of the Valhall For 9.2 m and continued to the base at 28.55 m. The mation in the North Sea and adjacent areas also palynological slides with the figured palyno occurs on seismic profiles offshore Helgeland morphs are housed in the Paleontologisk Mu (Fig. l) in equivalent stratigraphic position. This seum, Oslo (PMO). 'Late Cimmerian Unconformity' appears on Fig. 2 as an erosional surface with no angular dis cordance between the two units. During the sum Core description mer of 1982 the beds around the boundary were cored at 65°06.0'N, 10°17.3'E by the drilling ship The interval 28.55-11.00 m in core 7B (Fig. 3) 'Pholas' in a shallow drilling programme along consists of black homogeneous organic-rich E-W seismic profiles in the area. The strata are claystones. Neither sedimentary structures nor dipping gently to the west. This drilling pro bioturbation were observed. Some specimens of gramme is part of a mapping programme run by the bivalve genus Buchia occur. Smectite is the IKU (Maisey & Wøien 1983, Bugge, Knarud & dominant clay mineral. The total organic carbon Mørk 1984). content varies from 4 to 11%, and the rock has a rich hydrocarbon potential. Immature unstruc tured organic material is dominant, but palyno Material morphs and woody material also occur. At 11.00 m there is an abrupt lithological l'wo cores were recovered from the same site due change at a planar boundary (as seen in a core 5 to technical problems in the first hole. The tech cm in diameter) to an approximately 20 cm thick nique involves sampling by mechanical hammer light grey and grey intraformational conglomer ing through the outer drill string. Wire line coring atic limestone. The clasts and matrix are differen can start when reasonably well consolidated tiated on their colours, but interfinger and may strata have been reached. Only three hammer be difficult to distinguish. samples are available from the 5. 1 m deep core Above there are 25 cm of calcareous mudstone hole 7. Seven hammersamples were collected below another more well cemented micritic lime from the upper part (4.5-9.2 m) of corehole 7B. stone without intraclasts at 10.55 m. The calcite
2 Geologisk Tidsskr. 1/86 18 N. Aarhus et al. NORSK GEOLOGISK TIDSSKRIFT 66 (1986)
Fig. I. Sketch map showing location of boreholes in !KU shallow drilling programme 1982. Cores 7 and 78 (same location) are here studied. Roman numerals indicate seismic units. The location of Andøya is also shown. content is 90% at 10.45 m and decreases to 75% grey to redbrown associated with the disappear at 10.20 m from where it is further reduced to 15- ance of pyrite. 40%. Siderite and dolomite do not occur. At 7.30 Calcareous fossil fragments are few both in the m there is a colour change of the marl from light limestones and marls. A few Inoceramus frag-
w 150 E
Fig. 2. Shallow seismic line 878-103 with location of studied coreholes. Seismic interpretation by Tom Bugge. NORSK GEOLOGISK TIDSSKRIFT 66 (1986) Biostratigraphy Lower Cretaceous, Sklinnabanken 19
ments are found, some of them bored probably Gochteodinia vi/losa and Scriniodinium pharo by sponges (?Clionia). Fungal borings are pres which all are in accordance with a Ryazanian dat ent in woody fragments from all the nine very ing. S. grossii is common to abundant in the up small (except at 10.10 m) organic residues recov permost metre of the black shale, at 11.25 m to ered from the interval 10.30-9.35 m. These gether with Hysterichodinium voigtii. This is woody fragments may well be reworked from the probably a result of change in environment; the Ryazanian, whereas the rest of the reworked or luxuriance of these species is associated with the ganic material was less resistant and has not been incoming of a bivalve bottom fauna which pos preserved. sibly reflects improved circulation of water. Sam The redbrown calcareous claystone in the two ples at 12.60 and 11.51 m, however, do have high lower hammersamples (4.00-4.30 m and 5.00- proportions of phytane. Some workers take this 5.10 m) from corehole 7 is similar to that above as an indication of reducing depositional environ 7.30 m in corehole 7B. Reduction spots and In ment. The rich content of organic material (al oceramus fragments occur. There is a thin grey though unstructured) also suggests that reducing bed around 4.24 m. The redbrown hammersam or oxygen-poor bottom conditions still prevailed. ple at 2 m in hole 7 contains pebbles icedropped Possibly Buchia or some species of this genus in calcareous ela y similar to that below and repre could live in water with low oxygen content. But sents Quatemary cover consisting mostly of in we will not completely exclude the possibility situ or nearly in situ weathering products. that these shells may have been dropped into the sediment.
28.55-10.85 m Ryazanian Nannofossils Palynology Samples in the black claystone proved to be bar The occurrences of Batioladinium pomum (lam ren. The interval 10.95-10.85 m yielded a spe plughii zone, eastem England, but younger in the cies-poor nannofossil association dominated by Haldager borehole no. l) and B. radiculatum Ellipsagelosphaera spp. Of biostratigraphic sig (runctoni-icenii zones, eastem England) (Davey nificance is the presence of Palaeopontosphaera 1982) throughout the black shale unit point to an sa/ebrosa, Nannoconus colomi, Nannoconus glo age no older and hardly younger than Ryazanian. bu/us and Nannoconus steinmanni. Systematophora palmula, Stiphrosphaeridium ar Nannoconids have not been reported before bustum and Kleithriasphaeridum porosispinum from earliest Cretaceous strata of north-western from 23.32 m and upwards support a Ryazanian Europe. According to Deres & Acheriteguy dating. (1980), the above-mentioned nannoconids and Egmontodinium expiratum from the base to the absence of younger forms are characteristic 16.65 m, according to Davey, would restrict the for a Berriasian age. A remarkable element in age to the runctoni zone (earliest Ryazanian). both samples is Sol/asites arcuatus. In the Spee Other species in the core which occur consis ton Clay, this species is restricted to bed D6 (Ber tently and have extinctions similar to that of E. riasian) according to Black (1971) and our own expiratum are Stiphrosphaeridium dictyophorum observations. and Dingodinium spinosum. They are, however, not found below 25.60 m. We think they have Macrofossils some stratigraphic potential in the area. This is A fragment of an ammonite has been found at also the case for Systematophora palmula (pres 13.20 m and in the interval from 12.00-11.95m a ent in the albidum Zone in the Speeton Clay ac number of heavily crushed buchiid bivalves oc cording to Davey (1982)). In contrast to in Eng cur. In spite of the poor preservation, the mate land, it has a partly overlapping range with that rial gives a due as to the age of this part of the of E. expiratum and occurs to the top of the black core. shale. The recorded species thus conflict with some of the ranges in Davey (1982). Based on Surites sp. cf./aff. tzikwinianus (Bogoslovsky, macrofossil evidence, a middle Late Ryazanian 1897) tzikwinianus zone age seems likely at 13.20 m. 1897 0/costephanus tzikwinianus Bogoslov The unit is otherwise characterized by consis sky, p. 59, 141, pl. 2, figs. 6a-d. tently occurring Tubotuberel/a apate/a, Chlamy 1964 Surites tzikwinianus (Bogoslovsky): Do dophorella membranoidea, Sirmiodinium grossii, novan, p. 31, pl. 7, fig. l.
2' --- - <�C -�� �og�� !:5 g:�gM:co � RYAZANIAN >�:g����m � il"- "' l� ��l zm mm " � � ??: � � .� � � /!! .;;; ... :;: jO_ p .;; -;- "' �:D �"'... "" � �§� ""'-! eo ex l'l'':!il 1 1 1 1 1 1 , 1 li'i'i!:' !i':J' j l lllllll'llli!l ll jllll�l!ll'''lllll'''lllll'lll illill i'':j'':1 ! ::.:... w"'''''1111111!l!ilim:1111 111 1111 1111 ,11liii!i'1111111111!ii1111 1111l111111111111111!1�lli ll111111 1 11111fll11111 11111ll!liliiii'i1i!i!11111111111111111:i� 11,111!11:1:ww �ll><1Xll l l ::. 1 1 1 1 1 >< !��terii<: 6\ () Cl Cl ;;. �ru� � Rf2"'�i:>!l_ ��a� �h � � Black Grey --+ Redbrown -i 1 2-� il � "3 . . . . - . s."•• � . o . Cribroperidinium gn�nuløtum (Kiement) Stover& Evitt 1978 ...... ()o X Tubotubørwlla .,ute/a (Cookson & EiSØf'JM:k) loannidøs er al. 1977 . . . . Egmontodinium expin�tum O.vey 1982 . . . •O . . . o . . Bøtio/IKiinium pomum Davey 1982 ...... Dingodiniumr:tlf'viculum Cookson & Eisenøck 1958 . . . Cttlnidodinium 1p.
. • " lsthmocystis distincta Duxbury 1979 " . . . . . o . o o . . . Scriniodinium pharo (Duxbury) Davøy 1982 .. . . . o o . . . . . o() . . .. . Hystrichodinium pu/chrum/voigtii group . . . Cribropt�ridinium pøriorans (Cookson & EistJniiCk) Below 1981 ...... AptwxliniumIP· A Davey 1982 ...... O «:l . - Sirmiodinium grossii Alberti 1961 . . o o . o ...... X Sttntusidinium spp. � . . o . . . . o . . . X ChiMnydophorøllø m�mbranoidøa Vozzhennikova 1967 ...... BøtioiiKiinium r« . . . Fromuamphont Cookson & Eisenack 1958 . . Møndicodiniurn grottnl•ndicum (Pocock & Sllrjunt) Dllwty1979 z . Pøi'(J()(/ini•IP· 1 O.wty 1982 o . Sysrøm•tophontsp. 1 Dawty 1982 . . .. c; . . . o o o X X GochttiOdini• viiiOSII (Vozzhønnikova) Norris1978 ::0:: ...... X Egmontodinium torynum (Cookson & Eisenack) Oøvey 1979 o ...... rn X Dingodiniumspin0$Um (Duxbury) Davey 1979 o . . . . . X . bptodiniumspp ...... Oavey o Kløithriasph.øridium porosispinum 1982 o5 ...... (Cookson Stiphrophøridium dictyophorum & Eiænack) D11vey 1982 til . . -- Pai'(J()(/inia verrucosa (Vozzhennikova) Wiggins 1975 ::0:: ...... X WallodiniumkrotzSJChii (AibertiJ Habib 1972 . ::l Occiwcysta t.ntoria Duxbury 1977 o . Vl GochttiOdlni• cf. mutøbilis Vl . . ::0:: Sy•r.møtophora sp.2 DIIVfl'l 1982 ---- :>a . . . . Cøaicul01phøridiø m.,nø O.vey 1974 . . C.nningiø comphl Oavey 1982 . • Splniføriffll 11Jni0$US (Ehrenberg) Loøblich & Loeblich 1966 � . � . Gonyaulacysta diutina Duxbury 1977 . • . Pa�nyaulacysta borealis (Bridf!aux & Fisher) Stoll'llr & Evitt 1978 � :!l z � Gony.ul«ystø hølicoidøa (Eisenøck & Cookson) Sørjeønt 1966 o Systemøtopho,. pølmu/11 Dsvey 1982 ;.:l ,.., Vl l • Apreodinium conjunctum EiSIIrNICk & Cookson 1960 "C � a. Stiphrof()hMridium ørbustum D•vey 1982 Cl '<" Cleisrcuphøridium tribulihrum (SarjtNmt) Dsvey et øl. 1969 tTl o 0/igt»p/J..,.idlum dilucu/um Davey1982 o o r Egmontodinium polyp/.:hophorum Git�Mz & Sarjeant 1972 o �· . a. l o Cleistosphøridium .".�tum Mclntyre & BridHux 1980 Cl .... Gony.u/.:ysra-tp. A BrldNux 1977 v; ;>:: § Mu�rongiø timpløx ·AI�rti 1961 '\"l KleithriMPhøridium corruø-tum Døvey 1974 ::l n o .... Gonywl.:ym .""_ Zøhiri 1981 Vl "' � 1978 Vl :l o o Ch81mydoph /la trøbøculou (Gocht) Davey � a 0/igorphøridiumpørlmatum (Gocht) Oøvey & Williøms 1969 � 3 Pr!lludoc.ratiumpøllifMJm Gocht 1957 � Ctenidodinium .t.-ntulum Millioud 1969 n � Nelchinoplis kOitromitmsis(Vozzhttnnikova) Wiggins 1972 � � 1975 ..... Bøtio/Miinium longicomutum (Aibørti) Bridtlwx "' B.micropodum (EiS#n«k & Cookson} Briduux1975 f " Apr.odlnium gtMullltum Eiønack 1958 Q...... P.IWOdin;.tp. ((Jf'Bnul•rJ 0:1 Spinit.ritrn dflntørus (GochtJ Løntin & Willillml 1973 . Trichodinh.Jm c.r.n.um (D�fl•ndn} CIBrkø & V�rdier 1967 o Cyclon.phølium diltinchJm O.fl•ndre & Cooklon 1955 Cribf'OIWridinium mudørongøn• (Cookson& EisenackJ DaVf!y 1969 tx:l Aldorf;. spongloa (Mclntyrø & BrideauxJ Davey 1982 §' Sys�m•tophora si/yl» Oavey 1979 � CøsicuiOI{)hMJridi• røticul•t11 DaWiy 1969 �· Lirhodini•stowri (MillioudJ Duxbury 1977 .... CltliltOSPhMJridium hu(IUoniotii fV•I�nsi) Davev1969 {5 • St.,Niodinium spinu/osum Duxbury 1983 o Trichodinium cifi•tum (GochtJ Eisen«k 1964 � Gonywi«Yitll !Ntiøi•t• Duxbury 1977 t""' o o OligoiPhøridium complttx (White) Daww & Williams 1966 Aptøodinium cf. rtlticulatum � • ?Chytroeisphllflridia sp . Cløistotlphøridium •ncoriftlrum (Cookson & Ei•n.ck) Davey øt •1. 1966 !? ProtoellipiOdinlum spinosum Dawy & Vtlrdiør1971 æ:; Gonyaulacysta pørlorobtusø Duxbury 1977 AdnatCJtiPhøridium sp. § o o 8 T.".,.,Mtitrn F o o � Ptttrrnpermøll• o Solitph•ridium � ScoltJCodonts s= Forwnini� linin11 ;:: CymBriOIPh•,.. spp. 1:) fP. "" CiclltricOiiiPOritft l:) Boring�in woody ".."".nrs ;:: � N ..... � � Hauteriv�n l Upper Hl!uterivian - Lower Barremian 'fl' HilV•�f��� l ;5 "' m m m m � .. "' o u. l o Ul u. o "' o "' o z ;<: § -· eo 00 o o . ••• • •• •• Eflip�losphatN"II Spp � " o. •• • •• ••-+ O.LIIppiHWit1931 •• Nannocrxws colomi l:> .g o •• 00 .. . . P•l�ntosp/IMI'Iul� (BI«k 1971} Prim& SJJSingh 1977 ;;. i» • •• • ••• • ••. •••• o 8/.clc 1911 " . Rør«:� •ngusrifor11t11 o o. . .. • • o • . �· o � 0000 o o o 00 •• o o S�ph#nolithion lllfittt'li Not!/ 1956 � § . C r11tar1Ybdus conicvs Bnmløtt11& M11rtini 1964 So/IMitn horricus (Str»dtwr,A tUmikK & MIIIWCh 1966) 8/«k 1968 � ... lo o .. Sollll5itn arcu11tus 8/.ck 1911 � Gram11rh11bdus mflddii Bl«k 1971 � N•nnoconus globulus Brånninvnn 1955 " N11nnoconus srøinmanni KMnptMr 1931 :r .. ••O• • S111urolithn C/lJ)( (!Hflllndrf1954} C..tini 1963 ::l BrurudosphHr.J r�l11ris BfiiCk 1973 a Nannoconus kamptl1flri BrOnnimMm 1955 • Nannoconus btlrmucMzi Br6nnirrJMII'I 1955 3 o • Nannoconus boflf!ti T�o 1959 8 Ntlflnoconusneinmanni minor OøtBAchiri�y & 1980 Greenland it is confined to a leve! between Sur ites analogus and Bojarkia mesezhnikovi (Surlyk 1978). The occurrence of this fragment seems thus to indicate the presence of Upper Ryazanian at this leve!. Buchia cf. volgensis (Lahusen, 1888) 1888 Aucella volgensis Lahusen, p. 16, pl. 3, figs. 1-1 7. 1978 Buchia volgensis (Lahusen): Birkelund, Thusu & Vigran, p. 56, pl. 4, figs. 1-4; pl. 5, figs. 4-6. 1978 Buchia volgensis (Lahusen): Surlyk, p. Fig. 5. Fragment of Surites sp. cf./aff. tzikwinianus (Bogos lovsky, 1897) at 13,20 min core 7B. PMO 113.363. 32, pl. 6, figs. 1-5. 1981 Buchia volgensis (Lahusen): Zakharov, p. 125, pl. 37, figs. 5-7; pl. 38, figs. 1-3; ?1965 To /lia (To/lia?) aff. simplex (Bogoslov pl. 39, figs. 1-4; pl. 40, figs. 1-2; text-fig. sky): Jeletzky, p. 38, pl. 8, fig. 8. 23. 1978 Surites tzikwinianus (Bogoslovsky): Sur 1981 Buchia volgensis (Lahusen): Zakharov, lyk, p. 32, pl. 7' fig. l. Surlyk & Dalland, p. 264, pl. l, fig. 5. 1979 Surites cf. tzikwinianus (Bogoslovsky): 1982 Buchia volgensis (Lahusen): Surlyk & Mesezhnikov et al., p. 68, 70, pl. l, fig. Zakharov, p. 740, pl. 75, fig. 2. 10. 1984 Buchia (Buchia) volgensis (Lahusen): Kelly, p. 58, pl. 10, figs. l, 3, 4, 7, 8. The single fragment from 13.20 m (Fig. 5) is heavily distorted. Coiling is fairly evolute. The The Buchia material consists of a few crushed ribbing pattern is best seen on a east of the im specimens from the 12.00-11.95 m interval. The print. The ribs are sharp and bifurcate or, in a only fairly well preserved specimen shows a few cases, trifurcate on the middle of the flanks. slightly crushed right valve with part of the umbo They seem to show a forward bend ventrally and of the left valve preserved. Another heavily dis a single constriction is developed. torted specimen has a convex left valve and a The coiling and the ribbing pattern are in good much less convex right valve. agreement with representatives of the genus Sur Buchia volgensis is widely distributed in the ites from the S. tzikwinianus Zone. The fragment Boreal Realm and is known as far south as the compares well with material referred to S. tzik southern Caspian Sea in Asia and as far south as winianus from East Greenland by Donovan California in the Pacific (see distribution map in (1964) and Surlyk (1978). A Surites sp. from the Zakharov 1981, p. 130). same leve! as S. tzikwinianus described from East The stratigraphy of B. volgensis has most re Greenland by Donovan (1964, p. 32, pl. 7, figs. cently been discussed by Zakharov (1981), Zak 2-5) shows occasional constrictions, as does the harov et al. (1981), Surlyk & Zakharov (1982), present species. There is also a similarity with the Kelly (1984) and Jeletzky (1984). specimen figured by Mesezhnikov et al. (1979) In most parts of the Boreal Realm the species from the Petshora River Basin. has its first occurrence in the Hectoroceras kochi Surites tzikwinianus is a Boreal species, known Zone. It reaches its main abundance in the Sur from East Greenland, the Russian Platform, Si ites analogus Zone and has its last appearance in beria (Taimyr, Anabar-Katanga, Petshora) and the Bojarkia mesezhnikovi Zone. possibly also from Vancouver Island, Canada This is in good accordance with the occurrence (see discussion in Saks et al. 1972, p. 114 and Je of Surites sp. cf./aff. tzikwinianus 1.20 m below. letzky 1984, p. 217). Surites tzikwinianus characterizes the S. tzik JO. 75-10.20 m Lower Valanginian winianus Zone of the Russian Platform and de fines a leve! above the Surites analogus Zone of Palynology Siberia (see Mesezhnikov et al. 1979). In East We have recorded no marine palynomorphs in 24 N. Aarhus et al. NORSK GEOLOGISK TIDSSKRIFf 66 (1986) the Iimestones at 11.00 and 10.40 m. However, a striata is probably a combination of the ranges of poor assemblage with Scriniodinium pharo is Cretarhabdus loriei (sensu Sissingh 1977) with present at 10.36 m. According to Duxbury (1977) Polypodorhabdus madingleyensis and Cretarhab and Davey (1979, 1982), S. pharo ranges no dus striatus as mentioned by Taylor (1982). Based higher than earliest Valanginian. on the work of Sissingh and on experience from the North Sea, we assume that the lowest occur Nannofossils rence of this form in the Lower Cretaceous is of At 10.75 m, a nannoflora of mainly nannoconids stratigraphic significance. lts taxonomic situation and Ellipsagelosphaera spp. is met. The deepest and relation to the Jurassic Polypodorhabdus occurrence of Nannoconus kamptneri, Nannoco madingleyensis have to be checked, however. nus bermudezi and Nannoconus boneti and the Coccoliths are poorly represented in the deeper presence of Nannoconus steinmanni minor are part of the interval, but Nannoconus spp. are evidence of a Valanginian age. In the overlying very numerous. Nannoconus biicheri is abundant limestone unit (samples 10.40 m and 10.20 m) the at 10.00 m. This species occurs at a few localities nannoconids lose their predominance, but in in the Hauterivian, but has a more extended dis other aspects there is no change in the nannofos tribution during the Barremian and Aptian sil association. (Deres & Acheriteguy 1980). Nannoflora diversity increases markedly at 9.80 m. At this leve! the deepest occurrence of 10.20-9.00 m Hauterivian Conusphaera mexicana and Actinozygus geome Palynology tricus is logged. In the South European province, A diverse dinocyst flora with Batioladinium long these species occur from the earliest Cretaceous icornutum, B. micropodum, Muderongia sim and Late Jurassic respectively, whereas in Great plex, Pseudoceratium pelliferum, Gonyaulacysta Britain they occur from the Early Hauterivian ang/ese, Nelchinopsis kostromiensis and Chlamy noricum Zone (Taylor 1982). dophorella trabeculosa as the most age-significant species occurs at 10.10 m and indicates a regale Zone or younger Hauterivian age. M. simplex 8.20-4.00 may, according to Davey (1979), restrict the age m Upper Hauterivian - Lower Barremian to the middle part of the Hauterivian (regale-gott schei Zones). Palynology Thus a hiatus representing Late Valanginian An assemblage with Sirmidodinium grossii occurs and Early or earliest Hauterivian may be located at 8.00 m and points to an age no younger than between 10.10 and 10.36 m, probably at the lith Barremian. S. grossii is also present at 4.13 and ological change at 10.20 m. 4.00 m in core 7. The recovery in the samples above 10.10 m is The assemblage at 8.00 m includes Lithodinia much reduced. Nine samples between 10.00 and stoveri, Gonyaulacysta ang/ese and G. fastigiata. 8.00 m are barren or nearly so with respect to Duxbury (1977) found L. stoveri only in latest palynomorphs. Hauterivian strata, but may occur higher (Rene ville & Raynaud 1981). G. ang/ese occurs in the Nannofossils Hauterivian and in the earliest Barremian in the In grey marl that is found immediately over the Barremian stratotype (Zahiri 1981). previous sample at 10.20 m, Ellipsagelosphaera The assemblages of most samples from the red spp. and Palaeopontosphaera salebrosa are domi brown marls of both core 7 and 7B are character nant or very numerous in all samples. Nannoco ized by Oligosphaeridium complex (grading into nus biicheri at 10.00 m and Retecapsa striata at O. asterigerum), Trichodinium ciliatum, T. cas 9.90 m give evidence of a Hauterivian age. We taneum, Cyclonephelium distinctum, Apteodi prefer, however, to situa te the stratigraphic nium granulatum (occasionally tabulated), Ellip boundary at the lithological break at 10.20 m, un soidictyum imperfectum and Systematophora sil der the assumption that the absence of index yba. Most of these species are not very age sig forms in the deepest samples has been caused by nificant, although T. ciliatum according to Davey less favourable conditions in the early stage of a (1979) does not range above early Barremian. new sedimentary cycle. The more diverse assemblage at 4.20 m in hole The range of the species logged as Retecapsa 7 includes several pre-Aptian elements such as NORSK GEOLOGISK TIDSSKRIFT 66 (1986) Biostratigraphy Lower Cretaceous, Sklinnabanken 25 Ctenidodinium elegantulum, Occisucysta tentoria reason we assume that the sections between the and Gonyaulacysta fastigiata. breaks each represent a sedimentary cycle. The The presence at 4.20 m also of Muderongia logged earliest occurrences do not lead to a simplex does, according to Davey (1979, 1982), straightforward age conclusion. It is possible that indicate an early Late Hauterivian age to the top the nannofossil association variations of these cy of the core. Additional evidence suggestive of the cles largely testify to reworking and resedimenta Hauterivian is the presence of Gonyaulacysta tion. Several earliest occurrences of taxa are perforobtusa, which Duxbury (1977) found only noted that occur in the Hauterivian according to in the Hauterivian, and the lack of exclusively Ta ylor (1982), e.g. Chiastozygus striatus, Tegu Barremian and younger species such as Odon mentum stradneri and Tranolithus gabalus. Part tochitina operculata. of the evidence is consistent with a Barremian or The earliest Valanginian and older Scriniodi younger age, e.g. the earliest occurrence of a nium pharo at 4.03 min core 7 and Gochteodinia characteristic Nannoconus assemblage (Perch villosa (forms very similar to those recorded from Nielsen 1979, Deres & Acheriteguy 1980). On the Ryazanian strata below) at 7.03 and 5.25 min the other hand, the presence of an assemblage of 7B suggest reworking. Braarudosphaera spp. and isolated occurrences of Rucinolithus irregularis and Cribrosphaerella Nannofossils primitiva might imply an even younger age, e.g. Three samples from the hammer-core at 8.20- Aptian. 8.00 m yielded numerous 5-7 sided discs of There are several possibilities for error, be slightly irregular symmetry. These objects are cause of the character of the studied section and strongly reminiscent of fragments of Nannoconus our imperfect knowledge of Early Cretaceous abundans, but undamaged specimens have not nannofossils and their ranges. At present we as been found. In Great Britain, Nannoconusabun surne that the best nannofossil evidence is in fa dans is mentioned from the latest Hauterivian vour of a Late Hauterivian -Barremian age. and Barremian (Perch-Nielsen 1979, Ta ylor Several features deserve comment. Braarudos 1982). According to Deres & Acheriteguy phaera spp., which is encountered from 7.25 m (1980), the full range of this species is Barremian upward, occurs nearly exclusively in the form of and Aptian. The presence of Palaeopontosphaera segment fragments. These fragments were ini salebrosa in the same samples necessitates some tially related to Braarudosphaera hockwoldensis, comment. According to Taylor (1980), the latest implying an Aptian age (Perch-Nielsen 1979). occurrence of this species is situated in the ear Because of the predominance of fragments, we liest Barremian. However, Sissingh (1977) gives suppose that the form of the pentalith segments a latest occurrence in the Lower Hauterivian could very well be an artifact. Common Braaru (zone 4a). Black (1971) and Perch-Nielsen (1979) dosphaera as observed may be related to mar did not find this species in the Speeton Clay in ginal marine conditions and may have little bio strata younger than Hauterivian. In our corehole stratigraphic significance. 7B, this species is common to abundant from 9 m Nannoconus spp. are well preserved in the in downward, but clearly less common in the 8.20- terval under discussion. Nannoconus grandis, N. 8.00 m interval. It is possible that this species is aquitanicus, N. truitti frequens and N. truitti truitti reworked he re. Similarly, reworking could have occur simultaneously at 7.36 m. The correlation affected the range of this species elsewhere in the of this assemblage with other sections reveals North European basins, where sedimentation some discrepancies. It is probable that a typical breaks are not uncommon in the Lower Cretace Nannoconus assemblage developed in the Early ous. Barremian (Perch-Nielsen 1979). According to The interval from 7.36 m to 4.50 m consists of Deres & Acheriteguy (1980), the Nannoconus four hammer-cores separated by unsampled in truitti group has its earliest occurrence in the Ap tervals. The nannofossil distribution chart shows tian. Ta ylor (1982) mentions no Nannoconus at a pattern of earliest occurrences that is suggestive all before the Late Hauterivian in Great Britain. of several minor breaks, e.g. one below 7.36 m, In the Barremian, she logs Nannoconus abun one between 7.36 m -7.30 m, one below 6.17 m dans as only representative, whereas an enriched and one between 4.80 m - 4. 70 m. In-between assemblage that also contains Nannoconus truitti, these breaks, the nannofossil associations of con reappears in the Late Aptian. secutive samples are quite homogeneous. For this The discrepancies that are mentioned may ::s ,....,....r.J'JQ)""' O 50m N o 0\ �=-l'fa-· =Q.c:>:> ::1. "' DRAGNESET Fm K �r.fl� "'1 ('b ..... � NYBRUA Fm S ARSTEIN Fm L ' Sk·erm r ithostratigraphy :<: Ratjønna Mb Leira Mb v · ordelva M t ��8Qo-i'fo t kenMb h t:Q1ellneMb 1 = � ..... � ,....1=1 (l) o· � �Q,) r-. � ""TT"T"T11"'1'l"nt""'T""TT'1 ,.,..,.,�o 1:> � = o ... Ul � � g i � � 3- -· :;;: a · a g"' c:» �o s � l:; :;.� o Q. �..,.,...... , ,....,"""'T �m ... ��� 3��23' ..... - U)(IO....,Ø) U1 3 � Scriniodinium crystallinum (Deflandrtl) Klamønt 1960 å El8, respectively. The latter is indicative of the Discussion Lower Valanginian. The recovery in the upper part of the Nybrua Most workers have used the term 'Late Cimmer Formation is poor. Samples ElO and F9 are bar ian regional Unconformity' in the North Sea for ren. Ell, Fl and ES contain only age undiagnos the Kimmeridge ClayNalhall Formation bound tic Lower Cretaceous species. The presence of ary. The 'unconformity' represents everything Lagenorhytis delicatula (Fig. 8j) in F13 supports a from a latest Ryazanian or earliest Valanginian Valanginian age at this level (Duxbury 1977). F13 facies change, possibly induding a small hiatus in is located within an interval with Buchia sublaevis the Danish part of the Central Graben (Birke present in most samples and a left valve very lund, Clausen, Hansen & Holm 1983, Jensen, dose to Buchia crassicollis in sample Fl4 (Zak Heilmann-Clausen & Michelsen 1985) to a Kim harov, Surlyk & Dalland 1981). They stated that meridgian - Barremian (Johnson 1975) or even these two species do not occur together below the longer non-sequence in parts of the northern Upper Valanginian. North Sea. Chlamydophorella trabeculosa in sample Fl9 Rawson & Riley (1982) daimed that although points to a late Early Hauterivian or younger age a condensed sequence or a hiatus may occur at from this level (Duxbury 1977, Davey 1979, Pia basin margins or above structural highs over most secki 1981 ). Gonyaulacysta fastigiata is additional of the North Sea, the base of the Valhall Forma post-Valanginian evidence. Due to the recovery tion is conformable with underlying strata. Hes of an Upper Hauterivian - Lower Barremian as jedal & Hamar (1983) found no unconformity in semblage with Muderongia staurota and M. tetra the Norwegian-Danish Basin and centrally in the cantha in F21 and the Jack of Barremian evidence Central Graben. But condensed sequences or in Fl9, a Hauterivian age is likely for this sample. non-deposition occur towards the end of the Rya According to our experience Aptea anaphrissa zanian at the flanks of the Central Graben (Ha (common in F21) in northern areas probably has mar, Fjæran & Hesjedal 1983). a somewhat longer range than daimed by Dux In areas with continuous sedimentation, Raw bury (1977) and Davey (1979). The cooccurrence son & Riley (1982) and Hesjedal & Hamar in Andøya with M. tetracantha supports this. (1983) thought that the base of the Valhall For Odontochitina operculata in sample E3 indi mation represents an isochron. The abrupt cates a Barremian, probably Late Barremian or change seen on seismic profiles and in lithology younger age. In the Barremian stratotype Rene may be caused by a latest Rayzanian transgres ville & Raynaud (1981) found only scattered sion. Rawson & Riley (1982) also stressed the im specimens of this in the Lower Barremian, portance of eustatic sea-level changes for under whereas they recorded it consistently in the Up standing Lower Cretaceous sedimentation. per Barremian. We cannot exdude an Aptian age In the Sklinnabanken area, black shales were for this sample. deposited in the Upper Ryazanian prior to a re The recovery in sample El from the lower part gression which led to non-depostion and some of Nordelva Member is consistent with a late erosion down into tzikwinianus Zone beds. Re Barremian-Aptian age. Sample Gl from the newed sedimentation of marls seems to have Hellneset Member is Iocated about 165 m above started in latest Ryazanian. The depositional pat El and is out of scale in Fig. 6. It contains Mude tern is thus a dose parallel to that seen at basin rongia asymmetrica, Palaeoperidinium creta margins and structural highs in the North Sea. ceum, Apteodinium granulatum and Batioladi Zakharov, Surlyk & Dalland (1981), on the ba nium micropodum and common Chlamydopho sis of negative evidence, daimed that Lower and rella trabeculosa, Cribroperidinium muderon lower Upper Ryazanian were not represented in gense and Canningia cf. colliveri. This assem the Andøya section. Our data suggest that the blage is most likely Aptian in age although the Ryazanian sequence may be more complete. We evidence is not condusive. have not been able to document any definite in tra Ryazanian break in sedimentation, but there may well be one between samples 0163 and 0164. The unmappable unconformity in Figure 6 of Oalland (1981) below the few metres of Upper Ryazanian shales may be related to this level. These shales may well have been deposited sim- 30 N. Aarhus et al. NORSK GEOLOGISK TIDSSKRIFT 66 (1986) ultaneously with the intraformational conglomer otherwise sandy sequence may have been deposi atic limestone interval 11.00-10.80mi n core 7B. ted during this same transgressive phase. In J ameson Land (East Greenland) the kochi In Sklinnabanken we have assigned a Late Zone sediments (Hesteelv Formation) include Hauterivian- Early Barremian age for the lower both black shales ( coarser marginally in the ba part of clayey redbeds whereas they are Early sin), a sandy shell conglomerate and light mas Aptian in the Ling sub-basin and middle Albian sive or crossbedded sandstones at the top (Sur in the Rødby Formation of the North Sea (Raw lyk, Callomon, Bromley & Birkelund 1973). This son & Riley 1982). This shows that similar de sequence is slightly too old for being equivalent positional environments were developed at dif to the hiatus in other areas. Deposition of kochi ferent times in different areas. Such sediments Zone sediments in Jameson Land may therefore were probably not only deposited on the tilted have taken place in a relatively small basin which fault-block crests of Surlyk (1978). They may also was gradually filled by sediments of increasing well be related to transgressions at basin margins coarseness. in periods when sediment supply was low (Sklin Deposition of clay in Andøya in the uppermost nabanken). Both the Middle - Late Valanginian Ryazanian mesezhnikovi Zone continued across redbeds of Wollaston Forland, the Late Valan the RyazanianNalanginian boundary. Samples ginian-Hauterivian of Andøya, the Late Haute D172, D173 and E19 from the uppermost part of rivian-Barremian of Sklinnabanken and the mid Ratjønna Member are Valanginian in age. Albian redbeds of the North Sea may be asso Later in the Valanginian, deposition of sand ciated with transgressions. commenced in Andøya. Valanginian sandstones Palaebiogeographically the Ryazanian dinocyst are also known from Forth Approaches Basin floras from Sklinnabanken are closely related to (Devils Hole Formation), Wollaston Forland those from the North Sea area. The diversity in (Surlyk 1978), Trænabanken and Kong Karls the Ryazanian assemblages of Andøya is reduced Land (Bliithgen 1936). Surlyk linked his sand compared to that of Sklinnabanken and may sug stones to the major transgression at the Ryaza gest it is an assemblage transitional between nian/Valanginian transition, but according to our North Sea assemblages and the low diversity bo evidence at !east some of the sandstone unit in realis assemblage from the Ryazanian of Arctic Andøya correlates with the late Valanginian - Canada (Brideaux & Fisher 1976, Brideaux early Hauterivian hiatus on Sklinnabanken. 1976). Paragonyaulacysta borealis is present both Lower Cretaceous redbrown hematitic mud at Sklinnabanken and Andøya. stones occur both in East Greenland (Rødryggen Ryazanian assemblages from Tromsøyflaket Member of Surlyk (1978) in Wollaston Forland), seem to have characters in common with those in Andøya (Skjermyrbekken Member of Dalland from Andøya, but are poorly preserved. (1975)), in Trænabanken, Sklinnabanken and Håkansson, Birkelund, Piasecki & Zakharov Haltenbanken. Surlyk interpreted Rødryggen (1981) found a low diversity from poor to diverse Member as deposited in an oxidized environment dinocyst assemblages around this same strat on a submarine crest of a tilted fault-block. He igraphic leve! in Svalbard. assigned a Middle- Late Valanginian age. Zakharov, Surlyk & Dalland (1981) found Bu chia sublaevis in similar beds in Andøya. In northern Siberia this species ranges into the ear Conclusion liest Hauterivian bojarkensi Zone (Saks & Shul gina 1974). Palaeontological studies of a core from Sklinna Chlamydophorella trabeculosa in the upper banken and of Lower Cretaceous samples from most part of Skjermyrbekken Member in An Andøya show that the geology of these areas fit døya may according to evidence from eastern into a geological model governed by eustatic sea England (Davey 1979) suggest a mid Hauterivian leve! changes and tectonics. Sklinnabanken was or younger age. A transgression at about this more or less unaffected by structural movements leve! (Simbirskites inversum Zone) is in north and is therefore particularly useful for study of west Europe documented by mixing of boreal eustatic sea leve! changes. The latest Ryazanian and Tethyan ammonites (Kemper, Rawson & and mid-Hauterivian rises in sea leve! are best Thieuloy 1981). The Hauterivian shale in Milne documented. Land (East Greenland) of Piasecki (1979) in an Sedimentation at Andøya was more influenced NORSK GEOLOGISK TIDSSKRIFT 66 (1986) Biostratigraphy Lower Cretaceous, Sklinnabanken 31 by tectonic activity. The Ryazanian sequence is Cretaceous chalk deposits. Nettleton, Lincolnshire, England. more complete than hitherto considered. Deposi Rev. Esp. Micropaleontologie 8, 279--300. tion of marl on some structural highs commenced Casey, R. 1973: The ammonite succession at the Jurassic-Cre taceous boundary in eastern England. In Casey, R. & Raw before deposition of marine Valanginian sand son, P. F. (ed.), The Boreal Lower Cretaceous. Geo/. J. started in some structural basins. The Skjermyr Spee. Iss. 5, 193-266. bekken Member at Andøya seems to include Dalland, A. 1975: The Mesozoic rocks of Andøy, northern both Upper Valanginian and Hauterivian strata. Norway. Nor. geo/. unders. 316, 217-287. Dalland, A. 1979: The sedimentary sequence of Andøya, The Upper Hauterivian-Lower Barremian se northern Norway - depositional and structural history. In quence is thin, leading to Upper Barremian-Ap Norwegian Sea Symposium, Tromsø, NNS 26, 1-31. Norsk tian sediments already in the lower part of the Pf(roleumsforening. Dalland, A. 1981: Mesozoic sedimentary succession at Andøy, Nordelva Member and continuing into the Hell northern Norway and relation to structural development of neset Member. the North Atlantic Area. In Kerr & Fergusson (ed.), Geol Ryazanian dinocyst assemblages from Andøya ogy of the North Atlantic Borderlands. Can. Soc. Petro/. and Tromsøyflaket seem transitional between Geo/. Mem. 7, 563-584. those recorded in North Sea areas/Sklinnabanken Davey, R. J. 1979: Thestratigraphic distribution of dinocysts in ' the Portlandian (la test Jurassic) to Barremian (Early Creta and the 'borealis assemblage of Arctic areas. ceous) of northwest Europe. AASP Contr. ser., 5b, 49--81. Davey, R. J. 1982: Dinocyst stratigraphy of the latest Jurassic to Early Cretaceous of the Haldager no. l borehole, Den mark. Danm. geo/. unders., ser. B, 6, 1-56. Acknowledgements. The studied cores were obtained on a NPD scientific licence issued for shallow drilling offshore Helgeland Davies, E. H. 1983: The dinoflagellate Oppel-zonation of the in 1982. Several oil compaines financed this mapping pro Jurassic-Lower Cretaceous sequence in the Sverdrup Basin, gramme. NTNF supported publishing (10.15241). We appre Arctic Canada. Geo/. Surv. Can. Bull. 359, 59 p. ciate the technical assistance and critical reading of colleagues Deres, F. & Acheriteguy, J. 1980: Biostratigraphie des Nanno at !KU. conides. Centr. Rech. Exploration-Production Elf-Aquitaine, Bull. 4, 1-53. Donovan, D. T. 1964: Stratigraphy and ammonite fauna of the Volgian and Berriasian rocks of East Greenland. Meddr. Grønland 154 (4), 34 p. Duxbury, S. 1977: A palynostratigraphy of the Berriasian to References Barremian of the Speeton clay of Speeton, England. Pal aeontographica B 160, 17-67. Birkelund, T., Clausen, C. K., Hansen, H. N. & Holm, L. Griin, W. & Allemann, F. 1975: The lower Cretaceous of Car 1983: The Hectoroceras kochi zone (Ryazanian) in the North avaca (Spain): Berriasian calcareous nannoplankton of the Sea Central Graben and remarks on the Late Cimmerian un Miravetes section. (Subbetic zone, Prov. of Murcia). Ec/. conformity. Danm. Geo/. Unders. Årbog 1982, 53-72. Geo/. Heiv. 68, 147-211. Birkelund, T., Thusu, B. & Vigran J. O. 1978: Jurassic-Creta Hamar, G. P., Fjæran, T. & Hesjedal, A. 1983: Jurassic strati ceous biostratigraphy of Norway, with comments on the Brit graphy and tectonics of the south-southeastern Norwegian ish Rasenia cymodoee zone. Pa/aeontology 21, l, 31-63. offshore. Geo/. Mijnb. 62, 103-114. Black, M. 1971: Coccoliths of the Speeton Clay and Sutterby Hesjedal, A. & Hamar, G. P. 1983: Lower Cretaceous strati Mari. Yorkshire geo/. Soc. Proe. 38/3, 381-424. graphy and tectonics of the south-southeastern Norwegian Black, M. 1972: British Lower Cretaceous coccoliths. 1.: Gault offshore. Geo/. Mijnb. 62, 135--144. Clay. Monogr. palaeontogr. Soc. (London) 12611 (Publ. Nr. Håkansson, E., Birkelund, T., Piasecki, S. & Zakharov, V. 534), 1-48. 1981: Jurassic-Cretaceous boundary strata of the extreme Black. M. 1973: British Lower Cretaceous coccoliths. I.: Gault Arctic (Peary Land, North Greenland). Geo/. Soc. Denmark Clay. Monogr. pa/aeontogr. Soc. (London), 127 (Publ. Nr. Bull. 30, 11-42. 537), 49--112. Jeletzky, J. A. 1%5: Late Upper Jurassic and early Lower Cre Bliithgen, J. 1936: Die Fauna und Stratigraphie des Oberjura taceous fossil zones of the Canadian Western Cordiellera, und der Unterkreide von Konig Karl Land. Grimmen (Pom British Columbia. Geo/. Surv. Canada Bull. 103, 70 p. erania), 75 p. Jeletzky, J. 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Fig. 7 a Apteodinium conjunctum 7B, Ryazanian 15,85 m PMO 113.309/1 Z30 500 X b Apteodinium granulatum 7, U.Haut.-L.Barr. 5,12 m PMO 113.310/1 V36 500 X c Oingodinium spinosum 7B, Ryazanian 11,47 m PMO 113.3ll/l H38/4 800 X d Occisucysta sp. A Oavey 1982 7B, Ryazanian 21,95 m PMO 113.31211 R35/2 800 X e Chlamydophorella nyei 7, reworked 2,20 m PMO 113.313/1 F38/3 800 X f Oingodinium spinosum 7B, Ryazanian 18,33 m PMO 113.314/1 H22 800 X g Chlamydophorella trabeculosa 7, U.Haut.-L.Barr. 4,20 m PMO 113.315/1 P25 800 X h Chlamydophorella membranoidea 7B, Ryazanian 21,95 m PMO 113.316/1 Z29 800 X Chlamydophorella trabeculosa 7, U.Haut.-L.Barr. 4,20 m PMO 113.315/2 034/1 800 X Fig. 8 a Apteodinium cf. reticulatum 7, U.Haut.-L.Barr. 5,12 m PMO 113.36211 R34/2 500 X b Apteodinium cf. reticulatum 7, U .Haut.-L.Barr. 5,00 m PMO 113.31711 U20 500 X c Cribroperidinium sp. Andøya, Valanginian E18 PMO 113.318/1 R13/1 500 X d Occisucysta tentoria 7B, Ryazanian 23,32 m PMO 113.319/1 021 500 X e Cribroperidinium granulatum Andøya, Ryazanian 0157 PMO 113.320/1 F27/2 500 X f-g Gonyaulacysta perforobtusa 7, U.Haut.-L.Barr. 4,20 m PMO 113.315/3 023/3 800 X h Leptodinium sp. 7B, Ryazanian 25,60 m PMO 113.321/1 R3212 800 X Gonyaulacysta diutina 7B, Ryazanian 21,95 m PMO 113.31212 L 35 800 X Lagenorhytis delicatula Andøya, Valanginian Fl3 PMO 113.32211 K39/2 500 X Fig. 9 a Trichodinium ciliatum 7B, U.Haut.-L.Barr. 5,00 m PMO 113.323/1 J28 800 X b Cribroperidinium muderongense Andøya, Valanginian El1 PMO 113.324/1 039/3 500 X c Occisucysta sp. A Oavey 1982 7B, Ryazanian 18,25 m PMO 113.325/1 F 35/2 500 X d Cribroperidinium sepimentum Andøya ES PMO 113.326/1 S27/4 500 X e Cribroperidinium perforans 7B, Ryazanian 21,95 m PMO 113.31213 X33 800 X f Apteodinium sp. A Oavey 1982 7B, Ryazanian 21,95 m PMO 113.31214 Fl7/2 800 X g Occisucysta sp. A Oavey 1982 7B, Ryazanian 21,95 m PMO 113.31215 037 800 X h cf. Gonyaulacysta sp. A Oavey 1979 7B, Ryazanian 18,33 m PMO 113.31412 020 800 X Fig. JO a Canningia cf. colliveri Andøya, U.Barr.-Apt. G1(E) PMO 113.327/1 T26/l 500 X b Sentusidinium cf. pilosum 7 4,10 m PMO 113.328/1 Z21/l 500 X c Kallosphaeridium agglutinatum Andøya 0171 PMO 113.329/1 034 500 X d Apteodinium sp. Andøya Fl9 PMO 113.330/1 U47 500 X e Canningia cf. colliveri Andøya, U.Barr.-Apt. Gl(E} PMO 113.327/2 034/3 500 X f Canningia cf. colliveri Andøya, U.Barr.-Apt. G1(A) PMO 113.33111 041 500 X g Cleistosphaeridium sp. (note 7B, Ryazanian 28,28 m PMO 113.33211 U25 500 X shape of archeopyle and bifurcate process in the upper left) h Cleistosphaeridium sp. 7B, Ryazanian 28,28 m PMO 113.33212 P2213 500 X Canningia attadalica Andøya, U.Barr.-Apt. El PMO 113.333/1 033/1 500 X i Muderongia cf. staurota Andøya F13 PMO 113.32212 B4012 300 X k Cleistosphaeridium sp. 7B, Ryazanian 25,60 m PMO 113.321/2 R35/2 500 X l Sentusidinium sp. 7B, Ryazanian 15,66 m PMO 113.334/1 L31/3 800 X m Muderongia asymmetrica Andøya, U.Barr.-Apt. G1(E) PMO 113.327/3 R33/2 300 X n ?Chytroeisphaeridia sp. 7B, U.Haut.-L.Barr. 5,00 m PMO 113.335/1 035 800 X o Muderongia simplex 7, U.Haut.-L.Barr. 4,20 m PMO 113.315/4 119 670 X p ?Chytroeisphaeridia sp. 7B, U.Haut.-L.Barr. 5,00 m PMO 113.335/2 V26 800 X Fig. 11 a Sentusidinium sp. 7B, Ryazanian 24,76 m PMO 113.336/1 F35/2 800 X b ?Leberidocysta sp. Andøya, U.Barr.-Apt. El PMO 113.33312 C25/l 500 X Canningia compta 7B, Ryazanian 18,33 m PMO 113.337/1 G25/2 800 X d Fromea complicata Andøya, U.Barr.-Apt. GI{A) PMO 113.33112 W39 500 X e Sentusidinium sp. 7B, Ryazanian 15,66 m PMO 113.334/2 W14/4 800 X f Sentusidinium sp. 7B, Ryazanian 21,95 m PMO 113.31216 Z28 800 X g Cleistosphaeridium sp. 7B, Ryazanian 11,57 m PMO 113.338/1 E39 500 X h Sentusidinium sp. 7B, Ryazanian 25,60 m PMO 113.321/3 S33 800 X 3 Geologisk Tidsskr. 1186 34 N. Aarhus et al. NORSK GEOLOGISK TIDSSKRIFT 66 (1986) Fromea sp. 78, Ryazanian 25,60 m PMO 113.32114 El5 500X i Cassiculosphaeridia reticulata 7, U.Haut.-L.8arr. 4,20 m PMO 113.339/1 Y2213 800X k Undescribed dinocyst 78, Hauterivian 10,10 m PMO 113.340/1 Y29/l 800X l Cassiculosphaeridia sp. Andøya, U.8arr.-Apt. E3 m PMO 113.34111 03811 500X m Fromea amphora Andøya, U.8arr.-Apt. Gl( A) PMO 113.331/3 L42 500X Fig. 12 a 8atioladinium radiculatum 78, Ryazanian 23,32 m PMO 113.319/2 K35 800X b Pareodinia sp. 78, Ryazanian 24,76 m PMO 113.34211 02212 800X c Paragonyaulacysta borealis Andøya, Valanginian El8 PMO 113.343/1 F2814 500X d 8atioladinium radiculatum 78, Ryazanian 23,32 m PMO 113.344/1 014/2 670X e 8atioladinium pomum 78, Ryazanian 19,55 m PMO 113.345/1 Cl9/l 800X f Paragonyaulacysta sp. Andøya, Ryazanian 0163 PMO 113.346/1 83112 500X g 8atioladinium micropodum Andøya, U.8arr.-Apt. Gl(E) PMO 113.327/4 G35 500X h Pareodinia verrucosa 78, Ryazanian 18,33 m PMO 113.314/3 E24/3 800X 8atioladinium micropodum Andøya, U.8arr.-Apt. Gl( A) PMO 113.33114 U23 500X i Paragonyaulacysta borealis 78, Ryazanian 18,33 m PMO 113.314/4 Z3811 800X k Stephodinium spinulosum 78, U.Haut.-L.8arr. 5,00 m PMO 113.335/3 S20/3 800X l 8atioladinium micropodum Andøya, U.Haut.-L.8arr. F21 PMO 113.347/1 H3112 500X Fig. 13 a Callaiosphaeridium asymmetricum 7, U.Haut.-L.8arr 4,20 m PMO 113.34811 R37/3 800X b Oligosphaeridium complex 7, reworked 2,20 m PMO 113.349/1 C34/4 500X c Cleistosphaeridium separatum 78, Ryazanian 13,40 m PMO 113.350/1 W38 800X d Cyclonephelium distinctum 7, U.Haut.-L.8arr. 5,00 m PMO 113.317/2 C29/4 800X e Solisphaeridium sp. 78, Ryazanian 18,25 m PMO 113.35111 X31/4 800X f Lithodinia sp. Andøya, U.8arr.-Apt. Gl(A) PMO 113.331/5 U2312 500X g Cicatricosisporites sp. 78, Ryazanian 23,32 m PMO 113.319/3 Xl6 800X h Woody fragment bored by fungi 78, Hauterivian 10,10 m PMO 113.340/2 J4112 500X Fig. 14 a Stiphrosphaeridium arbustum 78, Ryazanian 18,25 m PMO 113.35112 E30 500X b Systematophora palmula Andøya, Valanginian El8 PMO 113.31812 V25/l 500X c Systematophora palmula 78, Ryazanian 16,65 m PMO 113.35211Xl4/3 500X d Protoellipsodinium spinosum 7, U.Haut.-L.8arr. 4,20 m PMO 113.315/5 022 800X e Systematophora palmula Andøya, Valanginian 0174 PMO 113.353/1 W2214 500X f Oligosphaeridium diluculum 78, Ryazanian 15,66 m PMO 113.354/1 R27/l 500X g Kleithriasphaeridium porosispinum 78, Ryazanian 18,33 m PMO 113.314/5 V2113 500X h Systematophora palmula 78, Ryazanian 15,85 m PMO 113.355/1 M36/4 500X Systematophora silyba 7, U.Haut.-L.8arr. 5,00m PMO 113.317/3 Y24 800X i Systematophora sp. l Oavey 1982 78, Ryazanian 25,60 m PMO 113.321/4 V2012 500X k Aptea anaphrissa Andøya, U.Haut.-L.8arr. F21 PMO 113.356/1 P20/l 500X Kleithriasphaeridium porosispinum 78, Ryazanian 11,57 m PMO 113.357/1 K29/2 500X Fig. 15 a Systematophora palmula 78, reworked 5,25 m PMO 113.3581 Zl8 500X b cf. Surculosphaeridium sp. l 78, Ryazanian 18,25 m PMO 113.351/3 W3113 500X Oavey 1982 c Exiguisphaera plectilis Andøya, U.8arr.-Apt. El PMO 113.333/3X28/2 500X d Systematophora sp. 2 Oavey 1982 78, Ryazanian 16,65 m PMO 113.35212 W13/2 800X e Cleistosphaeridium ancoriferum 7, U.Haut.-L.8arr. 4,20m PMO 113.315/6 J2814 800X f-g Cleistosphaeridium huguoniotii Andøya ES PMO 113.359/1 N40/3 500X h Stiphrosphaeridium dictyophorum Andøya, prob. Ryaz. 0156 PMO 113.360/1 H29/2 500X Cymatiosphaera pachytheca 78, Ryazanian 16,65 m PMO 113.361/1 G34 800X i 8otryococcus 78, Ryazanian 16,65 m PMO 113.36112 800X k Tasmanites 78, Ryazanian 16,65 m PMO 113.361/3 F33/3 800X NORSK GEOLOGISK TIDSSKRIFT 66 (1986) Biostratigraphy Lower Cretaceous, Sklinnabanken 35 3' 36 N. Aarhus et al. NORSK GEOLOGISK TIDSSKR!Ff 66 (1986) NORSK GEOLOGISK TIDSSKRIFT 66 (1986) Biostratigraphy Lower Cretaceous, Sklinnabanken 37 38 N. Aarhus et al. NORSK GEOLOGISK TIDSSKR!Fr 66 (1986) NORSK GEOLOGISK TIDSSKRIFT 66 (1986) Biostratigraphy Lower Cretaceous, Sklinnabanken 39 40 N. Aarhus et al. NORSK GEOLOGISK TIDSSKRIIT 66 (1986) k NORSK GEOLOGISK TIDSSKRIFT 66 (1986) Biostratigraphy Lower Cretaceous, Sklinnabanken 41 g h 42 N. Aarhus et al. NORSK GEOLOGISK TIDSSKRIIT 66 (1986) NORSK GEOLOGISK TIDSSKRIFf 66 (1986) Biostratigraphy Lower Cretaceous, Sklinnabanken 43