Paleoflooding and paleoclimate of the Lower Meuse during the Allerød-early Holocene

Abstract

<p>Lateglacial climatic oscillations exerted profound impacts on the earth surface. In the Lower Meuse Valley (southern Netherlands), geomorphological studies in the last decades mainly centered on Lateglacial vegetation evolution, channel pattern changes and river terrace formation. Little information has been reported with respect to the paleohydrology and its relation with local and regional climate system. This study investigates a sediment core that contains flood sediments deposited from the Allerød to the middleHolocene. We conducted grain-size analysis, thermogravimetric analysis (organic matter and calcium carbonate content), pollen counting, macro fossils analysis, and oxygen and carbon stable isotopes analysis of the biogenic carbonate. Plant species variations in each pollen assemblage zone represent the local and regional vegetation development. The pollen and macro fossil studies reveal that the core site was in a lake and marsh environment through the Allerød-early Holocene period. The oxygen isotope record is believed to have captured the intra-Allerød Cold Period, its synchronous variation with the carbon isotope record indicates a dominant evaporation effect on the lake during the warm Allerød period. By highlighting the coarser components (flood signal) of the fine and coarse end members, two flooding energy indexes were constructed separately. The hydrological processes in the first phase of the Younger Dryas were characterized by rapidly increased flooding conditions and high accumulation rates. In the second phase of the Younger Dryas, an addition of aeolian sediments to the core site complicates the paleoflood identification. This work expands the paleoflooding reconstruction to a more broadly deposition setting where only fine or coarse fluvial sediment is the dominant component. The nearly synchronous changes of the increased flooding with the abruptly enhanced westerlies at the Allerød-Younger Dryas transition indicates a link between the Lower Meuse catchment and the regional North Atlantic climatic system</p>