Palynomorphs in the Northern High Latitude Cold Water Domain: A neogene stratigraphic and paleoenvironmental transect across the fram strait
Zusammenfassung der Projektergebnisse
Despite sucessfully drilling Neogene sediments during ODP Legs 151 and 162 and IODP Expedition 302, the Neogene paleoenvironmental evolution in the cold water domain of the Atlantic sector of the high northern latitudes is virtually unknown. Palynomorphs from three sites located along a transect from the seasonally-ice covered Nordic Seas to the perennial ice-covered Arctic Ocean have been studied to improve the stratigraphic correlation, to assess palecological preferences, and to unravel the paleoenvironmental history for the period between ~16 and 3 Ma. Palynomorph events (dinoflagellate cysts, acritarchs) have been calibrated to an independent chronostratigraphy of ODP Hole 907A and compared with published data from other sites in the Nordic Seas, North Atlantic Ocean, and adjacent shallow seas. Most of the 26 bioevents proved to be asynchronous across the high northern latitudes, and only a limited number are useful for stratigraphic correlation between various geographic regions. A supra-regional biostratigraphic zonation can therefore not be established but the synchronous bioevents may be useful for correlating zonations between regions. The paleoecology of extinct species has been characterized by compiling their biogeographic distribution in Neogene sediments based on published data and new data from ODP Hole 907A and IODP Hole M0002A. Special emphasis has been placed on the Batiacasphaera micropapillata complex that characterizes Miocene assemblages in the cold water domain of the northern high latitudes. The response of palynomorphs to the global cooling after the middle Miocene climate optimum has been studied in ODP Hole 907A from the Iceland Sea. A low resolution alkenone SST record reflects the global long-term cooling and indicates that this location is ideally suited for a paleoenvironmental study at a 100 kyr resolution. This climate deterioration is also expressed in the palynomorph record by changes in dominant species and disapperance of species. Distinct changes in assemblage composition occurred simultaneously with short-term excursions in stable oxygen records from the lower latitudes that are possibly related to changes in global ice volume in the Middle to Late Miocene. Some bioevents in the Late Miocene are obviously recorded both in the Iceland Sea and the Central Arctic Ocean suggesting that major environmental changes are recorded almost simultaneously along the path of cold waters flowing from the Arctic Ocean into the Iceland Sea. These events might have been related to the development of small-scale glaciations on Greenland. The variable concentrations of palynomorphs in the late Middle Miocene to Pliocene of the Central Arctic Ocean challenge the widely accepted view that a perennial ice cover must have existed since 13-14 Ma. Instead, the sea-ice cover must have been rather variable ranging from relatively open waters in summer to an almost year-round sea ice cover. Sustained periods of open water may have occurred in the late Middle to Late Miocene while prolonged periods of ice cover may have characterized the Pliocene.
Projektbezogene Publikationen (Auswahl)
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(2009). Pliocene Palaeoceanography of the Arctic Ocean and Subarctic Seas, Philosophical Transactions of the Royal Society of London A, 367(1886), 21-48
Matthiessen, J., Knies, J., Vogt, C., Stein, R.
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(2011). Deciphering the palaeoecology of Late Pliocene and Early Pleistocene dinoflagellate cysts. Palaeogeography, Palaeoclimatology, Palaeoecology, 309, 17-32
De Schepper, S., Fischer, E.I., Groeneveld, J., Head, M.J., Matthiessen, J.
