| dc.description.abstract | This thesis aims to make a reconstruction for the paleo-environmental changes and the alternation of the terrestrial and marine environments during the Early Pleistocene in the Southern North Sea Basin. The cored section contains both terrestrial and marine material, which allows to link the fluvial records to the shallow marine environment. Terrestrial signals may have been derived from two river catchments in Europe during the Early Pleistocene, the Eridanos paleo-river from the northeast and the Rhine-Meuse river from the southeast. The age of the base of the core is interpreted as Early Pleistocene, Middle-Gelasian (2.1 – 2.3 Ma). The Early Pleistocene is an important Sub-epoch because it covers the intensification of large scale glaciation on the Northern Hemisphere. Lisiecki and Raymo used stable oxygen isotope ratios to indicate global temperature and ice-sheet evolution, this has resulted in Marine Isotope Stages (MISs).
The standard chronostratigraphic subdivision for the Netherlands, largely based on the work of Waldo Zagwijn, is primarily based on pollen data. The records had been constructed in the Eastern part of the Netherlands, this had as complication that no marine influence is recorded in the cores. Furthermore, the records had been constructed using data from different sites, this makes the sites incomplete and hard to data with the isotopic records obtained from the deep sea. Different key-aspects are used to achieve the aim, those key-aspects are alternation between marine- and terrestrial environments; identify the characteristics of the Early Pleistocene glacial/interglacial cycles; recognize patterns in the vegetation assemblages; correlate with the MISs stack of Lisiecki and Raymo (2005); recognize different hiatus and reworking events and to find trends to correlate with regional data.
A palynological data set based on pollen and organic-walled dinoflagellate cysts are used to achieve the aim of the thesis. In the laboratory, 70 samples are prepared by removing carbonates, silicates and sieving to bring the sediment size to 250 – 10 μm. Microscopic analysis are performed by using a Leica DM 2500 microscope, palynomorph taxa are scored until a minimum of 200 pollen is achieved. The palynological analysis can be subdivided into three groups: Pollen&Spores, Algae and Dinoflagellate cysts. Together with the lithological and mineralogical data of Ding (2020) the paleo-environment is determined.
Based on quantitative palynological data, the section is subdivided into three intervals: Interval 1 dominated by marine palynomorphs, Interval 2 dominated by a tidal environment and Interval 3 by terrestrial palynomorphs. The marine dominance declines when going upwards in the core, Interval 3 consists almost no dinoflagellate cysts anymore. The change from a marine to a more terrestrial environment is also observed in the estimated water depth. The estimated water depth indicate a change from deep water to a fluvial environment. Interval 1 shows a continuous sedimentation pattern, while for the upper part more erosion is observed. The erosion is proved by the sharp grass peaks and the relative low sedimentation rate (0.02 cm/year) calculated by the δ18O – stack.
Five glacial/interglacial cycles are observed in the vegetational data, the cycles start with a high amount of grasses and some forest vegetation, typical vegetation for a glacial environment in the Early Pleistocene. The vegetational change towards an interglacial environment is to ferns, deciduous forest and Tsuga&Taxodium domination. Not every detail is studied, due to the high amount of possible erosion and reworking events a lot of material is missing. For future research it is good to make a good dating for the core and to do palynological research on a higher resolution to find more details. | |
