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Palaeontology and stratigraphy of the inoceramid species from the mid-Turonian through upper Middle Coniacian in Japan

Noda M., Matsumoto T.

Acta Geologica Polonica

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1998

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Vol. 48, no. 4

435-482

EN

Upper Cretaceous strata are well exposed in many areas of Japan, although good exposures through the Turonian/Coniacian boundary are not common. This paper focuses on six areas in Hokkaido, Shikoku and Kyushu and documents the stratigrophical distributions of inoceramid species. These data are used to summarise the stratigraphical ranges of Turonian/Coniacian taxa in Japan. In part 1 of the paper, 17 species are described, with some biometric data and phylogenetic interpretation. These species are: Inoceramus (Inoceramus) hobestensis NAGAO & MATSUMOTO, I. (I.) teshioensis NAGAO & MATSUMOTO, I. (I.) iburiensis NAGAO & MATSUMOTO, I. (I>) tenuistriatus NAGAO & MATSUMOTO, I.(I.) pedalionoides NAGAO & MATSUMOTO, I.(I.) lusatiae ANDERT, I.(I.) uwajimensis YEHARA, I. (Cremnoceramus) rotundatus FIEGE, I. (Cr.) ernsti HEINZ, I. (Cr.) deformis MEEK, I. (Cr.) lueckendorfensis TROGER, I. (Platyceramus) tappuensis nom., nov., I. (Pl.) szaszi NODA & UCHIDA, I. (Volviceramus) koeneni MULLER, Mytiloides incertus (JIMBO), M. mytiloidiformis (TROGER), and M. sublabiatus (MULLER). In part 2, the stratigraphical distribution and correlation of these species are discussed.

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Inoceramids and biostratigraphy at the Turonian/Coniacian boundary; based on the Salzgitter-Salder Quarry, Lower Saxony, Germany, and the Słupia Nadbrzeżna section, Central Poland

Walaszczyk I., Wood C.

Acta Geologica Polonica

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1998

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Vol. 48, no. 4

395-434

EN

The candidate Global Standard Stratotype-section and oint for the base of the Coniacian Stage, the Salzgitter-Salder section, Germany, and the Słupia Nadbrzeżna section, central Poland, provide together a continuous record of the inoceramid succession and events across the Turonian/Coniacian boundary interval, that can be correlated throughout Europe and beyond. The Turonian/Coniacian boundary interval marks a radical change from the Upper Turonian Mytiloides/Inoceramus - dominated fauna to the Cremnoceramus-dominated fauna of the tompost Turonian and Lower Coniacian. The Cremnoceramus clade is basically composed of three lineages: waltersdorfensis, with subspecies waltersdorfensis (ANDERT) and hannovrensis (HEINZ); deformis, with subspecies erectus (MEEK), dobrogensis (SZASZ) and deformis (MEEK); and crassus, with subspecies inconstans (WOODS) and crassus (PETRASCHECK). Rare Inoceramus species range throughout the boundary interval, and in the middle Lower Coniacian representatives of the genus Tethyoceramus SORNAY (non HEINZ) appear. Twelve species and/or subspecies of these genera are described and illustrated. The inoceramids provide the basis for the subdivision of the uppermost Turonian - Lower Coniacian boundary interval into 7 inoceramid zones. The upper Upper Turonian is divided into the Mytiloides scupini Zone and the Cremnoceramus waltersdorfensis Zone. In the Lower Coniacian the following zones are distinguished, in ascendin order: Cremnoceramus deformis erectus, C. waltersdorfensis hannovrensis, Cremnoceramus crassus inconstans, Cremnoceramus crassus + C. deformis deformis and Inoceramus gibbosus. The inoceramid marker proposed for the base of the Coniacian, formerly referred to as Cremnoceramus rotundatus (sensu TROGER non FIEGE) is a synonym of Cremnoceramus erectus (MEEK), and its first appereance marks the base of the deformis erectus Zone and the base of the Coniacian Stage. The Salzgitter-Salder section, despite some problems concerning a possible hiatus or condensation at the boundary represents the best avaiable potential stratotype for the Turonian/Coniacian boundary.

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Biostratigraphy and correlation of the Turonian - Coniacian succession and the Turonian - Coniacian boundary problem in the Far East Russia based on ammonites and inoceramids

Zonova T., Jazykova-Flidlider E.

Acta Geologica Polonica

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1998

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Vol. 48, no. 4

483-494

EN

The stratigraphy, ammonite and inoceramid content of the Turonian - Coniacian deposits of Far East Russia are presented. The evolution of North Pacific ammonites and inoceramids at the boundary of the two stages was studied and the levels of fundamental changes within the ammonite and inoceramid biota are recognized. The established palaeogeographic difference between the Sakhalin and the North-East region palaeobasins is reflected in the existence of two independent local zonal schemes. The main criteria of the Turonian-Coniacian stage boundary in the Far East of Russia were established on the basis of the two schemes. The Turonian/Coniacian (T/C) boundary is clearly marked by the change in the taxonomic diversity of the zonal inoceramid assemblages. It is defined at the base of the Inoceramus uwajimensis Zone. The appearance of the endemic ammonite species. Jimboiceras mihoense MATSUMOTO is the ammonite criterion for recognising the T/C stage boundary in Sakhalin. This is supported by occurrences of the cosmopolitan Coniacian genera Peroniceras and Forresteria.