Until recently there have only been a few observations of relative sea-level change from the inner Bredefjord area in southern Greenland. Here a new sea-level curve is presented from the Tasiusaq area based on data mainly from a sediment sequence from a marine embayment. Sea-level changes can be recorded in sediments as changed chemical composition, physical properties and macrofossil content. Isolation and transgression sequences have been identified using lithology, loss on ignition, XRF and macrofossil analysis. Selected stratigraphical levels were AMS-dated, and additional sea level data was extracted from GPS and tidal measurements. Special attention has been given to the relation between tide and depositional environment during sea-level changes. The results suggest a rapid regression of 26 m in the Tasiusaq area between 8750 and 8050 cal. yr BP, about 1000 years later than at the coast. The sea level fell below present day level at 8050 cal. yr BP. The regression continued and the sea level reached below 3.5 m below highest astronomical tide (m b.h.a.t.) at 7300 cal. yr BP where it remained until 1210 cal. yr BP. The present day sea level was reached again sometime during the last 500 years. The marine limit was determined to c. 40 m above highest astronomical tide (m a.h.a.t.). Comparisons of the marine limit in the Bredefjord area suggest that much of the land uplift occurred before the Tasiusaq area was finally deglaciated. The transgression started also more than 2000 years later in Tasiusaq than at the coast, despite the fact that Tasiusaq is situated closer to the Greenland Ice Sheet. This anomaly can be explained by differential effects from the collapse of the Laurentide Ice Sheet peripheral bulge and the Neoglacial readvance.
Student Paper