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  • 1
    facet.materialart.
    Unknown
    The Eemian stratotype locality at Amersfoort in the central Netherlands: a re-evaluation of old and new data (2000)
    Cambridge University Press
    Details
    Publication Date: 2000-08-01
    Description: In order to obtain a better understanding of the infilling of the Saalian glacial basins during the Eemian, particularly following the recent research in the Amsterdam Basin (Terminal borehole), it was necessary to re-investigate the type locality of the Eemian at Amersfoort. Both published and unpublished data from various biota (diatoms, foraminifers, molluscs, ostracods, pollen) provide new information on the changing sedimentary environments during the Eemian. Although the organic and clastic sediments of the infilling represent nearly all the pollen zones, the sedimentary sequence at Amersfoort is discontinuous: four breaks at least are recognised at the type locality.The successive sedimentary environments and the breaks in the record are linked with the transgression of the Eemian sea, the topographic position at the margin of an ice-pushed ridge, and the changes in hydrodynamic conditions. Local conditions, such as a sandy sea bed, shallow water and a reduced water exchange near the North Sea margin, influenced the salinity of the basin. Rib counts of Cerastoderma edule shells indicate a higher salinity at the end of the Taxus (E4b) and the beginning of the Carpinus (E5) zones than that present in the modern North Sea. Local conditions were responsible for the higher salinity following the climate optimum.During the Abies phase (the later part of regional pollen zone E5), the sea level had already fallen. The change from eu-trophic peat growth (with Alnus and Salix) to an oligotrophic Ericaceae/Sphagnum community at the end of the Eemian resulted from the change from a marine to a fresh-water environment, probably coherent with a deterioration of the climate.
    Print ISSN: 0016-7746
    Electronic ISSN: 1573-9708
    Topics: Geosciences
    Published by Cambridge University Press
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  • 2
    facet.materialart.
    Unknown
    The identity of Isocrassina, Laevastarte and Ashtarotha (Mollusca, Bivalvia, Astartidae) and their representatives from beaches and estuaries in The Netherlands and Pliocene strata in Belgium (2009)
    In:  Cainozoic Research vol. 7 no. 1-2, pp. 27-67
    Details
    Publication Date: 2024-01-12
    Description: The identity of the subgenera Isocrassina Chavan, 1950, Laevastarte Hinsch, 1952, and Ashtarotha Dall, 1903, of the genus Astarte Sowerby, 1816 in the family Astartidae (Mollusca, Bivalvia) is discussed. Isocrassina has been widely used for Pliocene species in the North Sea Basin. Here it is demonstrated, that this is based on a redefinition of this subgenus, which excludes its type-species. As the North Sea species differ considerably from the type-species of Isocrassina in aspects of ornament and details of the hinge, it is concluded that they should be placed in the genus Laevastarte. A slightly modified definition of Isocrassina and Laevastarte is given and both are raised to genus level. The morphological basis for Ashtarotha is quite weak and it is found doubtful if it should be maintained. The species now incorporated in Laevastarte, known from the beaches and estuaries in the province of Zeeland (The Netherlands) are described and extensively illustrated. The present study also includes in situ specimens from excavations in the Antwerp region (Belgium) as well as from some boreholes in Zeeland. One new species, Laevastarte ovatacostata n. sp., and a new forma, Laevastarte bipartita (Sowerby, 1826) forma confusa are introduced. Neotypes are designated for Astarte omalii De la Jonkaire, 1823 and Astarte basterotii De la Jonkaire, 1823.
    Keywords: Bivalvia ; Astartidae ; Astarte ; Isocrassina ; Laevastarte ; Ashtarotha ; Pliocene ; Miocene ; North Sea Basin ; systematics ; new taxa ; neotype designation
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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