Author	Engel, E.R.
Year	1992
Journal	Geologisches Jahrbuch, Reihe A, Heft 125, 139 pp.
Title	Palynologische Evidenz klimatrelevanter Ereignisse in miozänen Sedimenten des Nordatlantiks [Palynological evidence of climatically relevant events from Miocene sediments from the North Atlantic]

Abstract Engel, E.R., 1992; Palynologische Evidenz klimatrelevanter Ereignisse in miozänen Sedimenten des Nordatlantiks [Palynological evidence of climatically relevant events from Miocene sediments from the North Atlantic]. Geologisches Jahrbuch, Reihe A, Heft 125, 139 pp. Abstract Palynological investigations were performed on pollen and spores from DSDP Sites 408, 400A, 554 and 608 from the North Atlantic Ocean. This research was based on the analysis of pollen and spores as well as of dinoflagellate associations. By means of characteristic dinoflagellates, five assemblage zones were defined which led to the stratigraphic division of the profiles. The biostratigraphy based on planktonic foraminifera and nannoplankton is generally confirmed by using palynomorphs. Minor differences between the plankton foraminifera and dinoflagellates on the Early/Middle Miocene and the Upper Miocene/Pliocene boundary found at Site 408 and in the stratigraphy of Site 554 were observed. Comparative research on the stratigraphic distribution of Miocene dinoflagellates in different geographical areas not only confirmed the stratigraphic distribution but also extended their stratigraphic range. This extension applies to the dinoflagellates Samlandia chlamydophora, Labyrinthodinium truncatum, Achomosphaera andalousiensis, Ataxiodinium choanum, OpercuIodinium crassum, Filisphaera filifera and others. Therefore, their significance as a stratigraphic marker is limited. The composition of the terrestrial palynoflora is indicative of a general climatic deterioration during the Miocene of the North Atlantic Ocean. However, tropic/subtropic or thermophil elements indicate shortterm climatic changes that overlap the general cooling period. A comparision of characteristic taxa demonstrates the significance of the dinocysts as environmental indicators. Fluctuations in the concentration of palynomorphs suggest that the dinocyst/sporomorph ratio is controlled by ecological events. The number of sporomorphs, which progressively decreases from on- to off-shore, is paralleled with the increase of the diversity of the dinoflagellate spectrum. Monospecific dinoflagellate associations document a shallow water environment in the Early Miocene of Site 400A and in the Early Pliocene of Site 554, probably correlated with a drastic decline of the sea level. Resedimented flora in secondary deposits allows one to draw conclusions on the paleooceanic reworking processes. The influence of oceanic current systems is evident in the distribution pattern of the dinoflagellate associations. The current pattern of the North Atlantic ocean during the Miocene was controlled principally by three circulation events: 1. the influence of Mediterranean water, 2. the Greenland-Scotland-Overflow and 3. the intensification of the "Proto"-Gulf-stream.