Late Glacial and Holocene shore-level changes in the Aarhus Bugt area, Denmark

We propose a new relative shore-level curve for the Aarhus Bugt area, an embayment in eastern Jylland, Denmark, based on a compilation of published and new radiocarbon ages of organic material. Lakes existed in the area during the Late Glacial and Early Holocene. Lake level rose gradually until the region was inundated by the sea at c. 9000 cal. years BP. The relative sea level reached a high stand at about 6000 cal. years BP, when the local relative sea level was c. 3 m above present-day mean sea level. The Aarhus Bugt area was inundated by the sea later than the Limfjord area in northern Jylland, but earlier than the Lillebælt region in southern Denmark. The shore-level curves for these areas differ partly because the glacio-isostatic uplift was more pronounced in the Limfjord area than farther south and partly because the northern regions were inundated by the sea earlier than the southern areas

Northeast Greenland (79.4 °N): Ice-free shelf edge around the Last Glacial Maximum 25.5-17.5 ka

The size of the last glacial ice sheet on the Northeast (NE) Greenland shelf and its interaction with ocean circulation have been the subject of debate. Here we provide insights into the extent of the ice sheet around the Last Glacial Maximum (LGM) and investigate timing and strength of changes in the flow of Atlantic Water. The study is based on a multiproxy investigation of a marine sediment core, gravity core DA17-NG-ST01-019G, from 323-m water depth at the NE Greenland shelf edge at 79.4°N. We present benthic and planktic foraminiferal distribution data, AMS-14C dates, sedimentological (ice-rafted debris (IRD) and grain sizes), and geochemical (XRF) data in combination with geophysical (sub-bottom profiler) data. The oldest sediments at the study site are dated to 25.5–17.5 ka, encompassing the time frame from the beginning of the LGM to the early deglaciation. This part is overlain by sediments from the late deglaciation and Holocene. The deposits dating from the LGM are very rich in both planktic and benthic foraminifera and macrofossils of excellent preservation. The faunas show that the site generally was affected by a strong flow of relatively warm subsurface Atlantic Water during the LGM and Early Holocene. Conditions turned more polar with cold bottom water flow in the Middle–Late Holocene (c. 7.5 ka to Recent) with presence of mainly agglutinated benthic foraminiferal species. Our data from the LGM also indicate that the deposits were mixed by iceberg scouring, confirmed by the geophysical data showing extensive ploughing of the sediments on the outer shelf area. The results further indicate that the Greenland Ice Sheet did not reach to the edge of the NE Greenland shelf at 79.4°N during the LGM 24–18 ka

When were the straits between the Baltic Sea and the Kattegat inundated by the sea during the Holocene?

The timing of the flooding of the Danish/German/Swedish straits and the first marine influence in the Baltic Basin after the Ancylus Lake stage has been much debated. Here we present 47 new radiocarbon ages from sediment cores retrieved from Danish waters, ages that record the marine transgression of the area. Most of the ages are based on shells of marine molluscs, hence the ages are uncertain because we do not know the precise reservoir age in the past. We use a reservoir age of 400 years, which is based on dating of museum specimens collected live before testing of nuclear bombs. It appears from the ages that the Great Belt (Storeb AE lt) was inundated before The Sound (oresund). The oldest ages on marine shells from the northern part of the Great Belt region are about 8.9 cal. ka BP. From the central part of the Great Belt, the oldest ages are about 8.2 cal. ka BP, in Mecklenburg Bay 8.1 cal. ka BP and in the Arkona Basin 7.1 cal. ka BP. Sediments deposited prior to the occurrence of marine molluscs contain brackish-water ostracods (Cyprideis torosa and Cytheromorpha fuscata); the sediments are usually laminated and non-bioturbated mud. The brackish-water phase may have lasted 500-1000 years. The youngest lake deposits without signs of marine influence are dated to c. 8.8 cal. ka BP (central Great Belt), 8.7 cal. ka BP (Little Belt) and 8.5 cal. ka BP (Arkona Basin). We see no evidence for marine influence at c. 10 cal. ka BP as recorded by some studies from the Baltic Basin