Dinoflagellate cysts of the Middle-Upper Miocene Gram Formation, Denmark

S. Piasecki

    Publikation: Bidrag til bog/rapport/konferenceproceedingsBogkapitelForskning


    The dinoflagellate cysts of the Gram Formation provide the biostratigraphic framework for the determination of the age of the formation and reflect environmental and palaeoclimatic conditions during deposition. The age of the Gram Formation is Late Serravallian and Tortonian (late Middle Miocene to early Upper Miocene) estimated on the basis of dinoflagellate cyst biostratigraphy; the basal glaucony-rich interval is referred to late Serravallian, and the overlying clays, silts and fine-grained sands are assigned to the Tortonian. These age assignments are not consistent with the ages based on molluscs and the foraminifers; for example, dinoflagellate cysts indicate no Messinian strata in the Gram Formation whereas the foraminifer stratigraphy does. Such stratigraphic contradictions are discussed. Significant variations in the diversity and abundance of the dinoflagellate cyst assemblages are interpreted to reflect relative sea-level variations; maximum flooding is inferred in the basal Gram Formation followed by steady shoreline progradation such that the uppermost levels at the Gram locality represents a coast-near setting. In localities further to the west and south, more marine floras occur in the uppermost part of the formation. The dinoflagellate cyst assemblage reflects the cooling climate during deposition of the Gram Formation. Genera and species persistently present from the Palaeogene disappear up through the succession, probably reflecting the deteriorating climate. Species with tropical – subtropical affinity occur in the underlying Hodde Formation but disappear in the Gram Formation. However, the response of Neogene dinoflagellate cyst assemblages to climatic and environmental parameters are not well elucidated, and detailed interpretations of the Gram flora are premature.
    TitelThe marine Gram Formation at Gram, Denmark: Late Miocene geology and palaeontology. Part 1
    RedaktørerF. Roth, K. Hoedemarkers
    ForlagPalaeo Publishing and Library
    Antal sider17
    StatusUdgivet - 2005




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