Inoceramus

Abstract: The numerous oscillations in the high sea-levels during the Late Cretaceous have been plotted from the distribution of nodular chalks and hardgrounds in the British Chalk. The five widespread strong transgressive peaks recognised by Hancock & Kauffman in 1979 can now be dated: the early Late Albian peak was in the early part of the Subzone of Callihoplites auritus ; the Early Turonian peak was later than previously realised and lies early in the Zone of Collignoniceras woollgari ; the Coniacian peak was late in the age, about a third of the way up in the Zone of Inoceramus involutus , but is relatively weak; the Middle Santonian peak lies in the middle of the Zone of Uintacrinus socialis ; the Late Campanian peak lies early in the Zone of Belemnitella langei . For the highest part of the Cretaceous it is necessary to consider evidence from the continent. It is difficult to estimate how long sea-level-highs lasted, but several of the sea-level-lows were prolonged, with extensive erosion in regions marginal to the sea. There were two very marked regressive troughs: early late Turonian, ranging from the end part of the Zone of Collignoniceras woollgari to somewhere about the middle of the Zone of Subprionocyclus neptuni ; and the Late Maastrichtian fall which is difficult to quantify. Where there have been improvements in the accuracy and resolution of long distance correlations, the theory of eustasy has been further strengthened; but there are substantial disagreements with the much quoted EXXON curve after the Santonian.

Abstract: Stratigraphy, inoceramid paleontology and facies characteristics of the Turonian through Santonian deposits of the Central Polish Uplands are presented, on the basis of which 17 inoceramid zones are recognized and their position against the ammonite standard division is discussed. Apart from the Middle/Upper Santonian and Santonian/Campanian boundary all other stage and substage boundaries are well recognizable with the inoceramid fauna. Most of the inoceramids, comprising about 40 species, assigned to six genera, are monographed. Two species from the Turonian-Coniacian boundary interval are described as new: Mytiloides turonicus sp. n. and Inoceramus vistulensis sp. n. The Mytiloides labiatus group is thoroughly treated and particular members are discussed, to show that M. suhmytiloides (SEITZ) and M. subhercynicus (SEITZ), the widely cited species of this group, are invalid and thus should be rejected. The names Mytiloides opalensis sensu SEITZ (non BšSE) and M. duplicostatus sensu KAUFFMAN (non ANDERSON) are younger synonyms of M. kossmati (HElNZ). A revision of the whole genus Cremnoceramus is also presented. The stratigraphic scheme applied to the Turonian through Santonian deposits of the Central Polish Uplands allows to solve some regional problems, and to construct a unified chronostratigraphic facies scheme for the southern part of the epicontinental areas in Poland. The facies characteristics combined with the paleotectonic setting of the studied area is the base of the distinguishing of the four geotectonic-facies regions: the Circum-Sudetic Trap Basins, the Cracow Swell, the Danish Polish Trough, and the Russian Chalk Sea. The evolution of the studied areas during Turonian through Santonian time is assembled to indicate the primary role of tectonic movements of the Subhercynian phase of the Alpine orogeny.

Abstract: New 87Sr/86Sr analyses of macrofossils from 13 key marker horizons on James Ross and Vega Islands, Antarctica, allow the integration of the Antarctic Late Cretaceous succession into the standard biostratigraphic zonation schemes of the Northern Hemisphere. The 87Sr/86Sr data enable Late Cretaceous stage boundaries to be physically located with accuracy for the first time in a composite Southern Hemisphere reference section and so make the area one of global importance for documenting Late Cretaceous biotic evolution, particularly radiation and extinction events. The 87Sr/86Sr values allow the stage boundaries of the Turonian/Coniacian, Coniacian/Santonian, Santonian/Campanian, and Campanian/Maastrichtian, as well as other levels, to be correlated with both the United Kingdom and United States. These correlations show that current stratigraphic ages in Antarctica are too young by as much as a stage. Immediate implications of our new ages include the fact that Inoceramus madagascariensis, a useful ...

Abstract: The candidate Global Standard Stratotype-section and Point for the base of the Coniacian Stage, the Salzgitter-Salder section, Germany, and the SΠupia Nadbrzezna 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 topmost 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 ascending 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 appearance 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 available potential stratotype for the Turonian/Coniacian boundary.