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1

High-resolution Campanian-Maastrichtian carbon and oxygen stable isotopes of bulk-rock and skeletal components: palaeoceanographic and palaeoenviron-mental implications for the Boreal shelf sea

Wilmsen M., Niebuhr B.

Acta Geologica Polonica

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2017

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Vol. 67, no. 1

47--74

EN

A high-resolution latest Early Campanian to Early Maastrichtian carbon and oxygen stable isotope record from the northern German Boreal shelf sea based on 537 analyses of co-occurring belemnites, brachiopods, inoceramids, oysters, and bulk rock samples is presented. All samples are precisely related to their stratigraphic, systematic and facies backgrounds and form an integrated, nearly 10-myr-long dataset with considerable palaeoenvironmental and palaeoceanographical implications. Petrographic studies indicate that low-magnesium calcitic coccoliths and calcispheres (i.e., planktic carbonate) predominate the bulk-rock data (marl-limestone rhythmites and chalks), thus representing a sea-surface water signal, and that only minor diagenetic alteration of the carbonate muds took place. Based on TL and CL microscopy, the investigated belemnites are extraordinarily well preserved, which may in part be explained by their early diagenetic surficial silicification (container effect), while the other macroinvertebrate groups are all less well preserved. The (plankton-dominated) δ13C values of the marl-limestone rhythmites and chalks (+1.1 to +2.5‰), recording a surface water signal, compare well with the δ13C data of inoceramids while δ13C brach.values (+1.5 to +3.0‰) are heavier than the bulk rock data. The large variation in the δ13Cbel. (-0.1 to +3.6‰) is attributed to isotopic disequilibrium of the biogenic carbonate formed by the belemnite animal. The bulk rock δ18O values show a remarkable low scatter, supporting petrographic observation of only minor diagenetic stabilisation/cementation, and can be approximated with northern German shelf sea-surface temperatures of ca. 20°C for the Late Campanian (ca. -2‰ δ18O), being slightly cooler during the Early Maastrichtian. The δ18O values of the belemnite rostra are even less variable and quite rich in heavier 18O (-0.7 to +0.6 with a mean of -0.1‰ δ18Obel.) in comparison to bulk rock and other skeletal components. Based on their excellent microstructural preservation and non-luminescence, we conclude that the belemnite rostra are diagenetically unaltered and have preserved the primary δ18O signal of ambient seawater (12±2°C). In the absence of any indication for migration from cooler water masses and evidence for authochtonous populations we assume that the belemnites of the genera Belemnitella and Belemnella lived as nektobenthos near the sea-floor and thus record the temperature of the bottom mixed layer of the seasonally weakly stratified north German shelf sea at water depths of 100 to 150 m; the temperature gradient was thus 12.5–18.75 m/1°C. A conspicuous latest Campanian cooling event is evident in both sea-surface and bottom-water temperatures. The δ18O values of nearly all investigated benthic fossils lie between the isotope values of pristine belemnites and bulk rock, and, therefore, should be used for palaeotemperature reconstructions only with great care.

2

Revision of Hamites wernickei Wollemann, 1902 (Cephalopoda, Ancyloceratina) from the classic Lüneburg section (Upper Cretaceous, northern Germany)

Niebuhr B., Jagt J. W. M.

Acta Geologica Polonica

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2016

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Vol. 66, no. 4

627--644

EN

A re-examination of heteromorph ammonites of late Campanian age from the Zeltberg section at Lüneburg has demonstrated that the type series of Hamites wernickei in fact comprises two different species that are here assigned to the nostoceratid Nostoceras Hyatt, 1894 and the polyptychoceratid Oxybeloceras Hyatt, 1900. Nostoceras (Didymoceras) wernickei (Wollemann, 1902) comb. nov., to which three of the four specimens that were described and illustrated by Wollemann (1902) belong, has irregularities of ribbing and tuberculation and changes its direction of growth at the transition from the helicoidal whorls to the hook, which is a typical feature of members of the subfamily Nostoceratinae. Torsion of body chambers is not developed in hairpin-shaped ammonite species, which means that the species name wernickei is no longer available for such polyptychoceratine diplomoceratids. Consequently, the fourth specimen figured and assigned to Hamites wernickei by Wollemann (1902) is here transferred to Oxybeloceras and considered conspecific to material from the Hannover area (Lehrte West Syncline) as O. aff. crassum (Whitfield, 1877). In addition to the "Heteroceras-Schicht des Mucronaten-Senons" of Lüneburg (bipunctatum /roemeri Zone, upper upper Campanian), the geographic range of N. (D.) wernickei probably includes Upper Austria, Tunisia and the Donbass region, while O. aff. crassum is known from the Hannover area (northern Germany), southern France, northern Spain and Upper Austria.

3

Silicified sea life – Macrofauna and palaeoecology of the Neuburg Kieselerde Member (Cenomanian to Lower Turonian Wellheim Formation, Bavaria, southern Germany)

Schneider S., Jäger M., Kroh A., Mitterer A., Niebuhr B., Vodrážka R., Wilmsen M., Wood C. J., Zágoršek K.

Acta Geologica Polonica

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2013

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Vol. 63, no. 4

555--610

EN

With approximately 100 species, the invertebrate macrofauna of the Neuburg Kieselerde Member of the Wellheim Formation (Bavaria, southern Germany) is probably the most diverse fossil assemblage of the Danubian Cretaceous Group. Occurring as erosional relicts in post-depositional karst depressions, both the Cretaceous sediments and fossils have been silicified during diagenesis. The Neuburg Kieselerde Member, safely dated as Early Cenomanian to Early Turonian based on inoceramid bivalve biostratigraphy and sequence stratigraphy, preserves a predominantly soft-bottom community, which, however, is biased due to near-complete early diagenetic loss of aragonitic shells. The community is dominated by epifaunal and semi-infaunal bivalves as well as sponges that settled on various (bio-) clasts, and may widely be split into an early bivalve-echinoid assemblage and a succeeding sponge-brachiopod assemblage. In addition to these groups we document ichnofauna, polychaete tubes, nautilids and bryozoans. The fauna provides evidence of a shallow to moderately deep, calm, fully marine environment, which is interpreted as a largescale embayment herein. The fauna of the Neuburg Kieselerde Member is regarded as an important archive of lower Upper Cretaceous sea-life in the surroundings of the Mid-European Island.

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Facies and integrated stratigraphy of the Upper Turonian (Upper Cretaceous) Grossberg Formation south of Regensburg (Bavaria, southern Germany)

Niebuhr B., Richardt N., Wilmsen M.

Acta Geologica Polonica

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2012

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Vol. 62, no. 4

595-615

EN

The Upper Turonian Grossberg Formation of the Regensburg area (Danubian Cretaceous Group, Bavaria, southern Germany) has a mean thickness of 20-25 m and consists of sandy bioclastic calcarenites and calcareous sandstones which are rich in bryozoans, serpulids and bivalves (oysters, rudists, inoceramids). Eight facies types have been recognized that characterize deposition on a southward dipping homoclinal ramp: the inner ramp sub-environment was characterized by high-energy sandwave deposits (sandy bioclastic rud- and grainstones, bioclastic sandstones) with sheltered inter-shoal areas. In mid-ramp settings, bioturbated, glauconitic, calcareous sand- and siltstones as well as bioturbated, bioclastic wacke- and packstones predominate. The carbonate grain association of the Grossberg Formation describes a temperate bryomol facies with indicators of warm-water influences. An inferred surplus of land-derived nutrients resulted in eutrophic conditions and favoured the heterozoan communities of the Grossberg Ramp. Carbon stable isotope geochemistry cannot significantly contribute to the stratigraphic calibration of the Grossberg Formation due to the depleted and trendless bulk-rock [delta^13]C values, probably resulting from a shallow-water aquafacies with depleted [delta^13]C DIC values and low [delta^13]C values of syndepositional and early diagenetic carbonate phases. However, strongly enriched skeletal calcite [delta^13]C values support a correlation of the Grossberg Formation with the mid-Late Turonian positive Hitch Wood isotope event (Hyphantoceras Event of northern Germany). This interpretation is supported by biostratigraphic data and a range from the Mytiloides striatoconcentricus Zone into the lower My. scupini Zone is indicated by inoceramid bivalves. Both the base and top of the Grossberg Formation are characterized by unconformities. Sequence boundary SB Tu 4 at the base is a major regional erosion surface (erosional truncation of the underlying Kagerhoh Formation in the Regensburg area, fluvial incision at the base of the Seugast Member of the Roding Formation in the Bodenwohr area towards the north and northeast). It is suggested that this unconformity corresponds to a major sea-level drop recognized in many other Cretaceous basins below the Hitch Wood or Hyphantoceras Event. The transgression and highstand of the Grossberg Formation is concomitant to the deposition of the fluvial Seugast Member and the onlap of the marginal-marine. Veldensteiner Sandstein. onto the Frankische Alb. The unconformity at the top of the Grossberg Formation (late Late Turonian SB Tu 5) is indicated by a ferruginous firm-/ hardground and an underlying zone of strongly depleted [delta^13]C values. The abrupt superposition by deeper marine marls of the lower Hellkofen Formation (uppermost Turonian.Lower Coniacian) may be connected with inversion tectonics at the southwestern margin of the Bohemian Massif.

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Integrated stratigraphy of the Kronsmoor section (northern Germany), a reference point for the base of the Maastrichtian in the Boreal Realm

Niebuhr B., Hampton M., Gallagher L., Remin Z.

Acta Geologica Polonica

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2011

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Vol. 61, no. 2

193-214

EN

Results of detailed multistratigraphic analyses of the Campanian.Maastrichtian boundary section at Kronsmoor in northern Germany are summarised and calibrated with the GSSP at Tercis les Bains, southwest France. Additional markers for the definition of the boundary in the Boreal Realm are proposed, and a detailed carbon isotope curve around the Campanian.Maastrichtian boundary in the chalk facies of the Boreal epicontinental sea is presented. The C isotopic GSSP marker for global correlation is the markedly abrupt decrease of c. 0.7 [per mil] [delta^13]C directly at the Campanian.Maastrichtian boundary as dated by ammonites. In electronic borehole measurements the Kronsmoor section covers the SP peaks 53 to 64 and the base of the Maastrichtian being situated just below SP peak 60. The first occurrence (FO) of the ammonite Pachydiscus neubergicus, which corresponds to biohorizon 1 at Tercis, falls in the upper part of nannofossil Zone UC15, at both localities. Biohorizon 3 is the FO of the ammonite Diplomoceras cylindraceum, which first appears in the Upper Campanian of Tercis and at Kronsmoor enters significantly above the FO of Belemnella lanceolata, the conventional Boreal belemnite marker for the base of the Maastrichtian Stage. Based on ammonite evidence, the internationally accepted base of the Maastrichtian at Kronsmoor is located between the FOs of Diplomoceras cylindraceum (Upper Campanian) and Pachydiscus neubergicus (Lower Maastrichtian) c. 11 m above flint layer F 600, at which the first representatives of the belemnite genus Belemnella, in particular Bn. lanceolata occur. The latter thus is a Late Campanian species, appearing c. 450 ky prior to the ammonite-based boundary. The FOs of Belemnella pseudobtusa (sensu Schulz) resp. Belemnella obtusa (sensu Remin) directly at the boundary can be use as the coleoid proxy for the definition of the base of the Maastrichtian in the Boreal Realm. To define the boundary by benthic foraminifera the last occurrence (LO) of Neoflabellina praereticulata is suitable. Biohorizon 12, as defined at Tercis, involves the nannofossil Uniplanarius trifidus, however, at Kronsmoor this species is rare, occurs only sporadically and also significantly lower in comparison to Tercis. It is possible though to compare and correlate nannofossil events between Kronsmoor and Tercis using cosmopolitan taxa such as Broinsonia parca constricta and Eiffellithus eximius. The LO of the latter appears to be situated just above the boundary in both sections; it follows from this that the top of nannofossil Zone UC15 is of Early Maastrichtian age.

6

Occurrence and significance of Cenomanian belemnites in the lower Danubian Cretaceous Group (Bavaria, southern Germany)

Wilmsen M., Niebuhr B., Chellouche P.

Acta Geologica Polonica

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2010

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Vol. 60, no. 2

231-241

EN

The belemnite records of the lower Danubian Cretaceous Group (DCG, northeastern Bavaria, southern Germany) are compiled, taxonomically described and placed within the new integrated stratigraphic framework of the group. Three specimens from the lower Regensburg Formation (Saal Member) south of Regensburg can be assigned to Neohibolites cf. ultimus (d'Orbigny) and are dated as late Early Cenomanian (Mantelliceras dixoni Zone). Eight specimens represent Praeactinocamax plenus (Blainville) and occur in an event (plenus Event) in the lower Eibrunn Formation (Regensburg area) or basal Regensburg Formation (Roding area in the Bodenwohrer Senke). Biostratigraphy and carbon stable isotopes suggest that the belemnite horizon with P. plenus in the DCG has strictly the same chronostratigraphic position (mid-Late Cenomanian, middle Metoicoceras geslinianum Zone) as elsewhere in Central and NW Europe. The lithostratigraphic units of the lower Danubian Cretaceous Group (i.e., the Regensburg and Ebirunn formations), however, are characterized by a pronounced diachronism based on their time-transgressive (i.e., onlapping) deposition during the Cenomanian.Early Turonian transgression. The distribution of P. plenus around the Mid-European Island can be easily explained by migration around the positive area without the necessity of a marine strait across the Bohemian Massif.

7

Late Campanian nostoceratid ammonites from the Lehrte West Syncline near Hannover, northern Germany

Niebuhr B.

Acta Geologica Polonica

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2004

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Vol. 54, no. 4

473-487

EN

The nostoceratid ammonites Nostoceras (Didymoceras) postremum (BŁASZKIEWICZ, 1980) and Nostoceras (Didymoceras) varium (BŁASZKIEWICZ, 1980) are described from northern Germany for the first time. They appear with the second occurrence of Nostoceras (Bostrychoceras) polyplocum (ROEMER, 1841) in the upper portion of the Neancyloceras bipunctatum / Galerites roemeri Zone of the Lehrte West Syncline (Lower Saxony, east of Hannover), which is equivalent to the upper Belemnitella langei Zone of the chalk of Lńgerdorf-Kronsmoor (c. 50 km north of Hamburg). In northern Germany, this ammonite association appears c. 1 Ma earlier than Belemnella lanceolata, which marks the base of the Maastrichtian in belemnite terms, and c. 1.5 Ma earlier than the international base according to the first occurrences of Diplomoceras cylindraceum and Pachydiscus neubergicus at Lagerdorf-Kronsmoor.Assuming that the GSSP of the base of the Maastrichtian Stage at Tercis (southern France) equals the boundary of the U.S. Western Interior (radiometric age 71.3 . 0.5 Ma), Nostoceras (Bostrychoceras) polyplocum first appears in Europe c. 75 Ma before present.

8

Late Campanian and Early Maastrichtian ammonites from the white chalk of Kronsmoor (northern Germany) - taxonomy and stratigraphy

Niebuhr B., Esser K.

Acta Geologica Polonica

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2003

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Vol. 53, nr 4

257-281

EN

Hypophylloceras (Neophylloceras) velledaeforme (Schluter, 1872), Anagaudryceras lueneburgense (SCHLUTER, 1872), Saghalinites wrighti BIRKELUND, 1965, Pachydiscus (Pachydiscus) neubergicus (VON HAUER, 1858), Menuites cf. wittekindi (SCHLUTER, 1872), Diplomoceras cylindraceum (DEFRANCE, 1816), Baculites vertebralis LAMARCK, 1801, Baculites knorrianus DESMAREST, 1817, Acanthoscaphites tridens (KNER, 1848), and Hoploscaphites constrictus (J. SOWERBY, 1877) are described for the first time from Kronsmoor, the only continuous Campanian-Maastrichtian boundary succession of northern Germany. Combined with the slightly younger section at Hemmoor (30 km SW of Kronsmoor), thirteen ammonites species in all are known to date from the Maastrichtian. The material studied comprises species from the Upper Campanian Belemnitella langei to the Lower Maastrichtian Belemnella sumensis zones. Three species (Baculites vertebralis, Baculites knorrianus, Hoploscaphites constrictus) occur earlier here than elseswhere (e.g. Denmark). Menuites cf. wittekindi, formerly known only from the Nostoceras polyplocum Zone (Upper Campanian), occurs in the Belemnella lanceolata Zone at Kronsmoor. Pachydiscus neubergicus and Diplomoceras cylindraceum, two of twelve markers for the base of the Maastrichtian at Tercis (GSSP, southwestern France), have their first occurrences at Kronsmoor significantly above that of Belemnella lanceolata, the belemnite marker for the base of the stage. Compared with Tercis, were the stage boundary was recommended between the FOs of both ammonite species, the Campanian - Maastrichtian boundary at Kronsmoor seems to be located within the Belemnella pseudobtusa Zone. Thus, the first occurrence of the genus Belemnella is of Late Campanian age, appearing c. 540 ky earlier than the base of Maastrichtian as defined at the GSSP at Tercis.

9

Early Cenomanian (Cretaceous) inoceramid bivalves from the Kronsberg Syncline (Hannover area, Lower Saxony, Germany) : stratigraphic and taxonomic implications

Wilmsen M., Niebuhr B., Wood C.

Acta Geologica Polonica

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2001

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Vol. 51, nr 2

121-136

EN

An Early Cenomanian inoceramid bivalve assemblage collected from material excavated from a temporary exposure in the Kronsberg Syncline east of Hannover (northern Germany) is described. It consists of "Inoceramus" crippsi MANTELL, 1822, "I" hoppenstedtensis TROGER, 1967, Inoceramus virgatus scalprum BOHM, 1914 and I. virgatus virgatus SCHLUTER, 1877, as well as transitional forms between I. virgatus virgatus and I. virgatus scalprum and an apparently undescribed sulcate form. The inoceramid fauna is well preserved and very rich in individuals. Many of the inoceramids occur either as double-valved individuals or with the valves in close association and appear to be cocentrated in distinct layers. Co-occurring ammonites are Mantelliceras dixoni SPATH, Mantelliceras sp., Schloenbachia varians (J. SOWERBY), Hypoturrilities gravesianus (D'ORBIGNY) and Scaphites obliquus J. SOWERBY. Using event stratigraphy, the stratigraphic interval of the collected fauna can be assigned to the lower part of the Lower Cenomanian Mantelliceras dixoni ammonite Zone. It predominantly comprises material from the Inoceramus virgatus acme-event (the Schloenbachia/virgatus event of German event stratigraphy) at the top of the lower subzone (Mantelliceras dixoni & M. saxbii Subzone) of the dixoni Zone, which is known from the Lower Saxony, Cleveland (eastern England) and Anglo-Paris basins, where it invariably occurs in carbonate-rich rocks with low diversity faunas. The lithofacies and geochemistry of the strata are documented and the "Inoceramus" crippsi and Inoceramus virgatus groups are discussed, including the problematic provenance of the type series of Inoceramus virgatus scalprum.

10

The Upper Cretaceous succession (Cenomanian - Santonian) of the Staffhorst Shaft, Lower Saxony, northern Germany: integrated biostratigraphic, lithostratigraphic and downhole geophysical log data

Niebuhr B.

Acta Geologica Polonica

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1999

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Vol. 49, no. 3

175-213

EN

The Cenomanian to Santonian succession of the Staffhorst shaft, ca. 50 km south of Bremen, because of its structural position in the northern German Upper Cretaceous basin, is intermediate in character and fossil content between the pelagic sediments characterizing the Pompeckj Block in the north and the proximal sediments of the Lower Saxony Block in the south. The biostratigraphic subdivision of the shaft is based on inoceramids, echinoids, belemnites and foraminifera. The various biozonations and zonal boundaries used in the Boreal Realm are compared and applied to the zonation of the shaft succession, and the biostratigraphy of the individual fossil groups is described. A new inoceramid zone, that of Inoceramus gibbosus, is proposed for the topmost Lower Coniacian; and an echinoid assemblage zonation is introduced. The existing benthic foraminiferal zonation of the Middle Turonian to Santonian has been modified, with changed age assignments based on the macrofossil zonation. The proposed basal stage boundary criteria of the "Second International Symposium on Cretaceous Stage Boundaries" (Brussels, 1995) could be applied only in some cases. The proximity of the Staffhorst shaft to the trial borehole, situated only 39 m away, has permitted the Self Potential (SP) and Resistivity (R) logs to be uniquely directly calibrated against the lithostraligraphical and biostratigraphic succession of the shaft. The previous identification of some stage and substage boundaries on the logs of northern German boreholes based on foraminiferal zonation will need to be shifted by several tens of metres as a result of thid calibration.