Early-Holocene coastal environments and climate in southeast Sweden: a reconstruction based on macrofossils from submarine deposits

Abstract

Submarine organic deposits situated 0-15 m below present sea level off the southeastern Swedish coast of the Baltic Sea (Hanö Bay, 55°43'N, 14°12'E) were studied for their macrofossil content (plant, insect and mollusc remains) and radiocarbon dated. These deposits are interpreted as gyttja sediments that accumulated in shallow, elongated lakes behind beach ridges or coastal sand dunes. Coastal processes and a sea-level rise were involved in their genesis. Three distinct generations of coastal lakes (lagoons) were recognized: (1) at the end of the Yoldia Sea Stage between 9600 and 9400 BP at 15 m below present sea level; (2) during the time span 9000-8000 BP (after the Ancylus regression) between 12 and 7 m below present sea level; and (3) around 5500 BP (Litorina Sea Stage) slightly below present sea level. Pine was the dominant tree in these coastal environments until ca. 8500 BP when alder became common on waterlogged soils. The plant, insect and mollusc records suggest diverse coastal environments with a mixture of wooded and open vegetation on waterlogged or dry sandy soils, small shallow lakes, brooks and small rivers. A climate as warm as, or slightly warmer than today is inferred from the insect and mollusc data for the period ca. 9500-8000 BP. The implications of the investigation for the history of the shore displacement in south Sweden are discussed.