Geological Survey of Denmark and Greenland Bulletin 31, 2014, 31-34 31 Calcareous nannofossil and foraminifer biostratigraphy of the Campanian–Maastrichtian chalk of the Femern Bælt (Denmark–Germany) Emma Sheldon, Caterina Morigi and Sarah D. Møller A new study based on calcareous nannofossil and benthic and planktonic foraminifer biostratigraphy is presented for the upper Campanian – Maastrichtian chalk of the Femern Bælt (Denmark and Germany; Fig.1). The results are consist- ent with recent studies of the Danish chalk for this interval, allowing correlation across the Danish Basin and forming the basis for correlation further afield within the Boreal Realm. Numerous studies have been carried out recently on the up- per Campanian – Maastrichtian chalk of the Danish Basin, covering aspects such as sedimentology, depositional envi- ronment, macrofossil biostratigraphy, carbon isotope strati- graphy as well as nannofossil and dinoflagellate biostrati- graphy. However, very few published studies on foraminifers exist across this interval in this area. The 09.A.006, 09.A.007 and 09.A.008 boreholes (Fig. 2) were drilled in 2009 in prep- aration for construction of a fixed link across the Femern Bælt, which will connect Denmark to Germany (Rambøll Arup JV 2011). The boreholes penetrated glacial till, Pale- ocene–Eocene clay and chalk (Sheldon et al. 2012). Here, for the first time, the Boreal foraminifer biostratigraphy of the late Campanian – Maastrichtian interval is investigated and presented alongside nannofossil biostratigraphy. Geological setting and palaeogeography The Femern Bælt area is located to the south of the Ring- købing–Fyn High and is part of the German Basin (Fig. 1). During the Late Cretaceous the Danish area was part of the extensive epicontinental sea where cool-water carbonate dep- osition dominated. The Maastrichtian chalk was deposited at depths of 100–250 m (Surlyk 1997). Chalk distribution patterns are affected in the Danish area by folding, salt dia- pirism, non-deposition and erosion, especially in the south- ern region (Lieberkind et al. 1982). In the Maastrichtian to Danian, the area was situated at 44°–46°N (Smith et al. 1994). In the upper Maastrichtian of this part of the Danish area, two main facies types dominate: (1) relatively deep wa- ter basinal sediments comprising coccolith and foraminfera- rich pelagic chalk, and (2) shallow marine chalk with high diversity faunas dominated by bryozoans, echinoids, bivalves and brachiopods (Surlyk 1997; Hart et al. 2004). The upper Campanian – Maastrichtian chalk of onshore Denmark was until recently referred to the Tor Formation equivalent. The Tor Formation was established by Deegan & Scull (1977) as a Maastrichtian (locally upper Campanian) chalk unit in the Norwegian and Danish sectors of the North Sea. A new holostratigraphic analysis of the upper Creta- ceous chalk of eastern Denmark resulted in a lithostrati- graphic subdivision of the onshore chalk (Surlyk et al. 2013). However due to local facies variations this new subdivision cannot be applied to the chalk of the Femern Belt area with- © 2014 GEUS. Geological Survey of Denmark and Greenland Bulletin 31, 31–34. Open access: www.geus.dk/publications/bull Fehmarn South North Lolland09.A.006 09.A.00809.A.007 3 km 0 m 50 100 150 Quaternary deposits Folded and faulted Palaeogene clay Palaeogene Cretaceous Fig.1. Map of Denmark and northern Germany showing the location of the planned fixed road and rail link across Femern Bælt. L: Lolland, F: Fehmarn, FB: Femern Bælt. Fig. 2. Sketch south–north cross-section of the Femern Bælt area and the location of the boreholes (from Sheldon et al. 2012). 55° 10°E 100 km 14°E 57° Sweden Denmark Germany German Basin Danish Basin Norway L F FB 54° 56°N 58° Poland Ringkøbing–Fyn High 3232 out sedimentological analysis and the term ‘Tor Formation equivalent’ is retained here. Biostratigraphy From the 09.A.008 and 09.A.006 boreholes nannofossils and foraminifers from the Campanian–Maastrichtian were analysed; from the 09.A.007 borehole nannofossils from the upper Maastrichtian were examined. The southern North Sea foraminifer zonation of King et al. (1989) and the Bo- real nannofossil scheme of Burnett (1998) were applied (Fig. 3). Marker species are shown in Fig. 4 and biostratigraphic results on Fig. 5. Nannofossil zones – The co-occurrence of Orastrum campanen- sis and Eiffelithus eximius indicates the presence of UC15dBP at the base of core 09.A.008. Subzone UC15eBP is absent. UC16BP was defined by Burnett (1998) but recent studies of Danish Campanian–Maastrichtian chalks (Sheldon 2008; Thibault et al. 2012) question the reliability of the UC16BP marker spe- cies in the Danish area. The top of UC16aBP is defined by the last occurrence (LO) of Heteromarginatus bugensis. In the pre- sent study and in the Stevns-1 borehole, eastern Denmark, the LO of H. bugensis is below the LO of Tortolithus caistorensis (marker for top UC16bBP). Other studies (e.g. Fritsen et al. 1999) assign the LO of H. bugensis to the top of UC16cBP. The top of UC16bBP is defined by the LO of T. caistorensis, which is very rare in the Danish area. UC16aBP and b are not easily subdivided in the Danish area and alternative markers are sug- gested for the top of UC16bBP: the LO’s of Tortolithus hallii and Tortolithus pagei were successfully applied in the present study, positioned prior to the LOs of Broinsonia parca parca and Zeugrhabdotus praesigmoides (markers for the overlying UC16cBP). The top of UC16cBP is defined by the LO of Mono- marginatus quaternarius. The LO of B. parca parca as a top UC16cBP marker is a more reliable marker in this study. The LO of Z. praesigmoides as an additional top UC16cBP marker is confirmed in this study. The top of subzone UC16d BP is de- fined by the LO of Broinsonia parca constricta. The first occur- rence (FO) of Prediscosphaera mgayae as an additional marker C am pa ni an M aa st ri ch tia n Southern North Sea foraminifer zonation Boreal calcareous nannofossils FC S2 3 FC S2 2 La te C re ta ce ou s FC S2 1b a a b c a b c U C 16 U C 20 U C 15 d d B. draco B. miliaris N. frequens A. maastrichtiana C. daniae Cretaceous taxa L. quadratus R. levis T. orionatus B. parca constricta M. quaternarius T. caistorensis H. bugensis E. eximius A. bettenstaedti B. decoratus G. monterelensis b Palaeogene Epoch/ageAge (Ma) UC19 UC18 UC17 70 75 65 72.1 E M Lt Lt Lt 66.0 A B C D E F G H I J K L M N O P Q R S T U V W Fig. 3. Nannofossil and foraminifer zonations. The timescale is accord- ing to Gradstein et al. (2012). UCBP: Upper Cretaceous Boreal Province nannofossil zones of Burnett (1998), FCS: Cretaceous southern North Sea Foraminfers, shelf facies, including chalk, zones of King et al. (1989). Nannofossil and foraminifer zonations correlated using Fritsen (1999). Fig. 4. Sselected nannofossils and foraminifers from the Femern Bælt. A: Arkhangelskiella maastrichtiana. B: Prediscosphaera  stoveri. C: Neph- rolithus  frequens. D: Reinhardtites levis. E: Tranolithus orionatus. F: Prediscosphaera mgayae. G: Broinsonia  parca constricta. H: Monomargi- natus  quaternarius. I: Zeugrhabdotus praesigmoides. J: Tortolithus cai- storensis. K: Heteromarginatus bugensis. L: Orastrum campanensis. M: Bolivinoides draco. N: Pseudouvigerina cristata. O: Brizalina incrassata. P: Hagenowella paleocenica. Q: Bolivinoides draco giganteus. R: Bolivi- noides  decoratus.  S: Stensioeina pommerana. T: Angulogavelinella betten- staedti. U: Globotruncana arca. V: Gavelinella monterelensis. W: Globoro- talites micheliana. Scale bars, nannofossils: 5 µm, foraminifers: 0.1 mm. 33 in the middle of UC16d BP (Thibaut et al. 2012) is confirmed in this study. The LO of Tranolithus orionatus marks the top of UC17 BP. In the present study, the LO of this species occurred after the LO of Reinhardtites levis (the LO of which marks the top of the overlying UC18 BP). In Stevns-1 these species also occur in the ‘reverse’ order. The LO of R. levis marks the top of UC18BP, but in this study its LO is before that of T. orionatus. It is suggested that in the Danish area, UC17BP and UC18BP should be combined, using either the LO of T. orionatus or the LO of R. levis to mark the zone top. The LO of P. mgayae has been suggested as an additional marker for the top of this zone (Thibaut et al. 2012); this is confirmed in this study. UC19BP comprises the interval from the LO of Reinhardtites levis to the FO of Lithraphidites quadratus. The FO of L. quadratus defines the base of UC20aBP. The base of UC20bBP is defined by the FO of Nephrolithus frequens. The base of UC20cBP is defined by the FO of Arkhangelskiella maastrichtiana. The un- certainties surrounding the use of the FO of A. maastrichtiana as a marker are well-documented (e.g. Thibault 2010) and the two subzones are merged here. The first common occurrence of A. maastrichtiana is used to mark the base of UC20b-cBP in this study. The base of the Prediscosphaera stoveri acme within this combined subzone is also applied successfully in this study. The LO of Helicolithus trabeculatus was suggested as a supple- mentary marker for this level (Sheldon 2008) and is confirmed here. The FO of Cribrosphaerella daniae marks the base of UC20dBP, the uppermost subzone of the Maastrichtian. The co-occurrence of Chiasmolithus edentulus, Coccolithus pelagi- cus, Cyclagelosphaera alta and Neochiastozygus saepes assigns the base of the overlying Danian in borehole 09.A.008 to the upper Danian subzone NNTp4F (Varol 1998). Lower – up- per Danian subzones NNTp1A-4F are missing or were not sampled. Danian chalk in the Femern area was documented for the first time recently (Sheldon et al. 2012). Previously the southern limits of Danian deposits were thought to be farther to the north (Håkansson & Pedersen 1992). Foraminifer zones – The top of FCS23 is defined by the LO of Pseudotextularia elegans. Bolivinoides draco (s.s.) is an index species. The top of subzone FCS23a is defined by the FO of P. elegans. P. elegans is not seen in the present study, but rare occurrences of Bolivinoides draco were noted, indicating the Fig. 5. Nannofossil and foraminifer biostratigraphic correlations of the three boreholes at the Femern Bælt. 20 25 30 35 40 45 50 55 60 65 70 75 80 85 22 a- c 21 b 23 90 95 100 20 b- c 20 a Present 09.A.006 09.A.007 09.A.008 FO LO ForaminifersF N common A. maastrichtiana common A. maastrichtiana C. daniae and Danian flora L. quadratus T. orionatus, R. levis P. mgayae P. mgayae B. parca constricta Z. praesigmoides Tortolithus spp. H. bugensis O. campanensis, E. eximius N. frequens, common A. maastrichtiana P. cristata Total depth 100.6 m Total depth 50.1 m Total depth 99.9 m B. draco giganteus B. draco, Spirillina spp. A. bettenstaedti G. arca barren P. cristata S. pommerana H. paleocenica (black) H. paleocenica (black) N. frequens N. frequens L. quadratus L. quadratus T. orionatus, P. mgayae B. parca constricta R. levis P. mgayae M. quaternarius Tortolithus spp. Z. praesigmoides H. bugensis 20 b- c 20 a 19 17/18 16 d 16 c 16 b 23 FC S 22 a- b 21 -b 20 b- c 20 d 20 a 19 17 -1 8 16 c 16 b 16 a 15 d 16 d UCFCS F N F NN UC UCFCS Depth (m) B. draco, H. paleocenica (black) H. paleocenica (black) P. cristata Spirillina spp. B. draco giganteus,S. pommerana P. cristata barren G. arca, ? R. szajnochae G. monterelensis G. arca Globotruncana spp., A. bettenstaedti B. miliaris, A. bettenstaedti B. draco giganteus Nannofossils (First occurrence) (Last occurrence) 3434 presence of FCS23. In upper FCS23 the range of Hagenow- ella paleocenica and the FO of Spirillina spp. are additional markers in the present study. The LO of Stensioeina pommer- ana occurring towards the bottom of FCS23 (corresponding to the base of nannofossil subzone UC20aBP) in this study may also prove useful. The range of Pseudouvigernina cristata within FCS23 may prove to be another useful marker. The absence of P. elegans means that it is not possible to subdivide FCS23 in this study. The top of FCS22 is defined by the LO of Bolivinoides miliaris. FCS22 is divided into FCS22b, the top of which is defined by the LO of B. miliaris, and FCS22a, the top of which is defined by the LO of Angulogavelinella bettenstaedti. The LOs of A. bettenstaedti and B. miliaris oc- curred in the same sample suggesting the presence of only FCS22a, but the range of A. bettenstaedti within FCS22 could be useful. The top of FCS21 is defined by the LO (often a flood occurrence) of Reussella szajnochae. FCS21 is divided into FCS21b, the top of which is defined by the LO of R. szajnochae, and FCS21a, the top of which is defined by the LO of Gavelinella usakensis. G. usakensis was not found in the present study, indicating the presence only of FCS21b. The LO of Globotruncana arca at the top of FCS21 is an ad- ditional marker, as are the LOs of Gavelinella monterelensis and Globorotalites micheliana and FO of Brizalina incrassata at a slightly lower stratigraphic level. Conclusions The Campanian–Maastrichtian chalk of the Danish area has recently been studied intensively using calcareous nannofos- sils, applying the UCBP scheme. The studies underline the need for an amendment of the UC scheme for the Danish area. The present study highlights the need to reconsider the subdivi- sion of UC20bBP and UC20cBP based on the FO of Arkhan- gelskiella maastrichtiana. It is recommended for the Danish area to use the FO of common A. maastrichtiana to mark the base of UC20CBP. It may also be practical to merge UC17BP and UC18BP. Additionally the subdivision of UC16BP cannot be reliably applied in the Danish area. The Danian nannofos- sil assemblage in borehole 09.A.008 provides further evidence for the southerly encroachment of the Danian sea. The foraminifer zonation of the Late Campanian – Maas- trichtian is for the first time correlated with the nannofossil zonation based on the 09.A.006 and 09.A.008 cores (Fig. 5). In the absence of certain established FCS marker foraminif- era for the North Sea chalk, new zonal markers, e.g. Hagen- owella paleocenica, Pseudouvigerina cristata, Globotruncana arca, Gavelinella monterelensis and Globorotalites micheliana are used here in addition to conventional taxa for the Cam- panian–Maastrichtian chalk of Denmark, perhaps allowing correlation with the North Sea area, and further afield. References Burnett, J.A. 1998: Upper Cretaceous. In: Bown, P.R. (ed.): Calcareous nannofossil biostratigraphy. British Micropalaeontological Society Se- ries 5, 132–199. Deegan, C.E. & Scull, B.J. 1977: A standard lithostratigraphical nomen- clature for the central and northern North Sea. The Institute of Geo- logical Sciences Report 77/25, 36 pp. Fritsen, A. (ed.) 1999: A joint chalk stratigraphic framework. In: Joint chalk research program topic V 1. 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E-mail: es@geus.dk http://store.elsevier.com/The-Geologic-Time-Scale-2012-2-Volume-Set/isbn-9780444594259/ http://store.elsevier.com/The-Geologic-Time-Scale-2012-2-Volume-Set/isbn-9780444594259/ mailto:obe@geus.dk