Geological Survey of Denmark and Greenland Bulletin 31, 2014, 35-38 35 Palynological and microfossil biostratigraphy and palaeo- ecology over the Paleocene–Eocene transition, Femern Bælt, northern Germany Patrick Alexander Richardt and Emma Sheldon A palynological and micropalaeontological biostratigraphic and palaeoecological investigation has been carried out on the Paleocene–Eocene transition of core 10.A.057 from the Femern Bælt (Fig. 1). Initial investigations of boreholes from the Femern Bælt indicated that core 10.A.057 included a thick succession of Upper Paleocene – Lower Eocene clay (Sheldon & Nøhr Hansen 2010; Rambøll Arup JV 2011; Fig 2). Complete Paleocene–Eocene sections have been de- scribed from Jylland and the Storebælt (Heilmann-Clausen 1985, Laursen & Andersen 1997; Laursen & King 2000, Nielsen et al. 1986), but no detailed studies have been pub- lished on these successions from the Femern Bælt. Boreholes were drilled on Lolland in Denmark, under the Femern Bælt and on Fehmarn island, Germany from 2009 to 2011 as part of geological and geophysical investigations performed in preparation for the construction of a fixed road and rail link connecting Denmark and Germany. The boreholes penetrat- ed Campanian – Upper Eocene strata, overlain by Quater- nary deposits. Borehole 10.A.057 is located in the southern part of the Femern Bælt (Figs 1, 2). Geology and palaeoecology The Femern Bælt is located in the German Basin south of the Ringkøbing–Fyn High. During the Late Cretaceous, the Danish area was characterised by an epicontinental sea resulting in chalk deposition. The sea became more restricted in the early–middle Paleocene and several highs bordered the marine area (Clausen & Huuse 2002). Transgression during the Selandian resulted in clastic marine sedimentation and the North Sea, Denmark and the German Basin formed a partially enclosed shelf area. During the late Paleocene and Early Eocene, sediment deposition occurred in a relatively deep marine basin, at some distance from the shore. Intense volcanic activity caused by the opening of the North Atlantic resulted in deposition of ash and tuff layers during this pe- riod. The present distribution of the upper part of the Palaeo- gene sediments is a result of erosion and glaciotectonic defor- mation during the Quaternary (Fig. 2). In the 10.A.057 core, the very fine-grained clays of the Upper Paleocene Holmehus Formation and Østerrende Clay (informal lithostratigraphic unit of Nielsen et al. 1986) are overlain by the Lower Eocene Ølst Formation, which is characterised by dark grey clay with abundant layers of black volcanic ash (Heilmann-Clausen et al. 1985). © 2014 GEUS. Geological Survey of Denmark and Greenland Bulletin 31, 35–38. Open access: www.geus.dk/publications/bull Ringkøbing–Fyn High 100 km 14°E 57°N 55° Sweden Denmark Germany German Basin Norway Lolland Fehmarn Femern Bælt 10°E 10.A.057 Viborg-1 Bovlstrup Jylland Store- bælt North Sea Stolle Klint Fig. 1. Map of Denmark and northern Germany showing the location of the planned fixed road and rail link across the Femern Bælt and the loca- tion of borehole 10.A.057 at 54°31.8´N, 11°15.9´E. Fehmarn Lolland10.A.057 3 km 0 m 50 100 150 Quaternary deposits Folded and faulted Palaeogene clay Palaeogene Cretaceous Fig. 2. Sketch south–north cross-section of the Femern Bælt area showing the location of borehole 10.A.057. 3636 Biostratigraphy A total of 19 samples were analysed for dinocysts, diatoms, foraminifers and radiolarians (Figs 3, 4). The Danish Pale- ocene–Eocene zonation of the Viborg-1 cored borehole (Heilmann-Clausen 1985) and the North Sea zonation of Mudge & Bujak (1996) were used for the dinoflagellate cyst stratigraphy. The North Sea Cenozoic zonation of King (1989) was used for microfossils. Dinocysts The samples from 100.49 to 90.31 m are assigned to the Areoligera gippingensis Acme Subzone P5a (Mudge & Bujak 1996; Fig. 3). This subzone represents the uppermost part of zone V4 (Heilmann-Clausen 1985) and is equivalent to the uppermost part of the Holmehus Formation (Mudge & Bu- jak 1996). P5a is characterised by an acme of A. gippingensis and the presence of Eisenackia margarita. The top of P5a is defined by the top of the A. gippingensis acme. Nielsen et al. (1986) found low abundances of Deflandrea oebisfeldensis in V4 in a borehole from the Storebælt but Heilmann-Clausen (1985) did not find this species in V4. The boundary between V4 and the overlying V5 is tentatively placed, since relatively high abundances of A. gippingensis continue into V5. The samples from 90.31 to 79.42 m are assigned to the E. margarita Subzone P5b (V5) based on the last occurrence (LO) of E. margarita (Mudge & Bujak 1996). E. margarita has its LO in the Østerrende Clay (Nielsen et al. 1986). Zone V6, which is characterised by a dominance of the warm-water genus Apectodinium and an acme of Apecto- Fig. 3. Range chart showing the distribution (number of specimens) of dinocysts, diatoms, foraminifers and radiolarians from borehole 10.A.057. P: pyrite, A: ash layer. Observed outside counting Very rare (1) Rare (2–4) Common (5–14) Abundant (15–49) Dominant (>50) C hr on os tr at ig ra ph y Ea rl y Eo ce ne La te P al eo ce ne Li th os tr at ig ra ph y Ø lst F or m at io n H ol m eh us F or m at io n Ø st er re nd e C lay D an ish V ib or g di no cy st z on at io n V7 E1 b V5 V4 P5 a P5 b N or th S ea m ic ro fo ss il zo ne s M ud ge & B uj ak 1 99 4, B uj ak & M ud ge 1 99 6 N SP 4 / N SA 2 N SP 3 / N SA 1b Ac ho m os ph ae ra s pp . Co rd os ph ae rid iu m s pp . D ef la nd re a oe bi sfe ld en sis D in oc ys t s pp . M icr od in iu m c f. or na tu m Pa la eo te tra di ni um m in us cu lu m Sp in ife rit es ra m os us Sp in ife rit es s pp . H ys tr ich os ph ae rid iu m tu bi fe ru m Im pa gi di ni um s pp . O lig os ph ae rid iu m c om pl ex Th al as sip ho ra d el ica ta Ac ho m os ph ae ra c ra ss ip el lis Gl ap hy ro cy st a or di na ta Gl ap hy ro cy st a sp p. Gl ap hy ro cy st a di va ric at a H ys tr ich os ph ae rid iu m tu bi fe ru m b re vis pi nu m Al iso cy st a sp . 2 Cr ib ro pe rid in iu m s pp . O pe rc ul od in iu m s pp . Cr ib ro pe rid in iu m te nu ita bu la tu m U ni nd en tif ie d pe ri di no id c ys ts Ac ho m os ph ae ra a lci co rn u Ar eo lig er a gi pp in ge ns is Ac hi lle od in iu m la tis pi no su m Ei se na ck ia m ar ga rit a Pa la eo cy st od in iu m li di ae Ar eo lig er a sp p. Dinoflagellate cysts D ia to m s pp . Fe ne st re lla a nt iq ua Co sc in od isc us m or sia nu s m oe lle ri Th al as sio rir op sis w itt ia na Au la co di sc us a llo rg ei D ia to m s pp . f la t s ilic eo us H em ia ul us s pp . Tr in ac ria re gi na D ia to m s pp . f la t p yr iti se d Fe ne st re lla a nt iq ua (s m al l) Diatoms Sp iro pl ec ta m m in a sp ec ta bi lis Sp iro pl ec ta m m in a sp p. Ag gl ut . f or am in ife ra in de t Am m od isc us c re ta ce us Gl om os pi ra c ha ro id es Rh ab da m m in a sp p. Ba th ys ip ho n m icr or ha ph id us Ba th ys ip ho n sp p. Cy cla m m in a am pl ec te ns Cy cla m m in a ro tu nd id or sa ta Cy st am m in a pa uc ilo cu la ta H ap lo ph ra gm oi de s sp p. H ap lo ph ra gm oi de s wa lte ri H or m os in a sp p. La br os pi ra s cit ul a M ar ss on el la o xy co na Re cu rv oi de s sp p. Re op ha x sp p. Rh ab da m m in a ro bu st a Agglutinating benthic foraminifers Ra di ol ar ia ns Ce no di sc us s pp . 100 95 90 85 80 75 70 65 60 55 P P P P P P P P P P A A A P D ep th (m ) 37 dinium augustum, was not found in this study. A missing core section from 79.42 to 73.36 m could represent Zone V6, but V6 has not been observed previously in the Femern Bælt area (C. Heilmann-Clausen & H. Nøhr-Hansen, personal communication 2013). However, V6 is present in the Stolle Klint Clay, north-western Jylland. The base of the Apecto- dinium acme in the earliest Eocene is a global event and is coupled with a carbon isotope excursion denoting the start of the Paleocene–Eocene Thermal Maximum (PETM). The samples from 73.36 to 51.81 m are referred to Early Eocene D. oebisfeldensis Acme Subzone E1b (upper V7; Bu- jak & Mudge 1994). The interval from 66.18 to 51.81 m is characterised by a minor acme of Glaphyrocysta divaricata and a high abundance of Microdinium cf. ornatum (Fig. 3). Zone V7 is found in the upper part of the Ølst Formation (Heilmann-Clausen 1985). Foraminifers and diatoms The assemblages mainly consist of poorly preserved agglu- tinating benthic foraminifers and diatoms. Samples from 100.49 to 79.42 m are assigned to zone NSA1b. Most sam- ples only contain few foraminifers, but two samples from the upper c. 2 m contain rich faunas with Spiroplectammina spectabilis, Labrospira scitula, Ammodiscus cretaceus, Glomo- spira charoides, Marsonella oxycona, Cystammina paucilocu- lata, Recurvoides spp., Hormosina spp., Rhabdammina robu- sta, Cyclammina rotundidorsata, Haplophragmoides walteri, Bathysiphon spp. and Cyclammina amplectens. This assem- blage is known as the ‘Rhabdammina biofacies’. The shift from low to higher diversity benthic assemblages in NSA1b was also noted in the Bovlstrup borehole, eastern Jylland (Laursen & Andersen 1997) and was interpreted as a shift from very poor to slightly improved life conditions on the sea floor. A low-diversity diatom flora with pyritised Fenestrella antiqua (var. small) and Diatom spp. (flat) is also present, in addition to sponge debris and radiolarians (Cenodiscus spp.). NSA1 is assigned to the Holmehus Formation in Denmark (King 1989). Samples from 73.36 to 51.81 m are assigned to zone NSP4. The assemblages are dominated by resting spores of centric diatoms, comprising Coscinodiscus morsianus moelle- ri, Fenestrella antiqua, Diatom spp. (flat), Thalassiophora wit- tiana, Trinacria regina, Aulacodiscus allorgei and Hemiaulus spp. From 66.18 to 56.87 m pyritised and translucent dia- toms occur in equal numbers; above and below this level only pyritised specimens occur. This difference in preservation is probably due to variations in the oxygen level in the water column and the amount of sulphide present in the sediment (De Jonghe et al. 2011). Zone NSP4 also includes bryozoan Fig. 4. Selected fossils: A–C and F–I: foraminifers, D, E, J, K: diatoms, L–R: dinocysts. A: Ammodiscus cretaceous. B: Cyclammina amplectens. C: Cystammina pauciloculata. D: Coscinodiscus morsianus moelleri. E: Fenes- trella antiqua. F: Glomospira charoides. G: Haplophragmoides walteri. H: Labrospira scitula (front). I: Labrospira scitula (side). J: Trinacria regina. K: Trinacria regina (siliceous). L: Microdinium cf. ornatum. M: Piece of dinocyst. N: Areoligera gippingensis. O: Def landrea oebisfeldensis. P: Eisenackia margarita. Q: Hystrichospharidium tubiferum. R: Unidentifi- able peridinoid cyst. Scale bars: 100 µm (A–K), 20 µm (L–R). A B C D E F G H I J K M N O p L Q R 3838 fragments, fish teeth, Inoceramus fragments, sponge spicules and rare agglutinating foraminifers. NSP4 is assigned to the Early Eocene Ølst Formation (King 1989). Discussion and conclusions A dominance of agglutinating foraminifers of the ‘Rhab- dammina biofacies’ in subzone NSA1b suggests a middle to lower bathyal palaeoenvironment characterised by restricted water circulation, with low oxygen levels and a reducing en- vironment at the sea floor ( Jones & Charnock 1985; King 1989). The low oxygen level may have led to decreasing degra- dation of organic matter by bacteria and benthic organisms, giving rise to the dark grey colour of the Holmehus Forma- tion compared with those described by Heilmann-Clausen et al. (1985). A relatively high abundance of the supposed hetero- trophic dinoflagellate Deflandrea oebisfeldensis and the rich diatom flora in the Ølst Formation may be due to increased productivity in the surface layers perhaps due to enhanced upwelling in coastal areas. The rich diatom flora, preserved as resting spores, also suggests stressed sea-surface and sea- bed conditions, perhaps due to volcanic ash falls and periods of anoxia (Bidgood et al. 1999). The scarcity of agglutinat- ing foraminifers is probably due to reducing conditions at the sea floor. Schiøler et al. (2007) suggested that the Balder Formation (the North Sea equivalent of the Ølst Formation) was deposited in a restricted marine environment at upper bathyal depths with dysoxic to anoxic bottom conditions. In core 10.A.057, palynological biostratigraphy indicates that Zone V6 is absent, either due to erosion or non-deposi- tion, therefore the Paleocene–Eocene Thermal Maximum is not preserved at this location. A hiatus with V6 missing was noted in the Lillebælt area (Heilmann-Clausen et al. 1985), supporting the Femern Bælt data. However it is possible that Zone V6 is found in the missing core interval between 79.42 and 73.36 m. 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