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3 Acta Geologica Polonica

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

100%

Niebuhr B. , Esser K.

Acta Geologica Polonica

2003

tom Vol. 53, nr 4

257-281

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.

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

100%

Wilmsen M. , Niebuhr B. , Wood C.

tom Vol. 51, nr 2

121-136

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.

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

84%

Niebuhr B.

Acta Geologica Polonica

1999

tom Vol. 49, no. 3

175-213

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.