Submerged Landscapes in the Hanö Bay : Early Holocene shoreline displacement and human environments in the southern Baltic Basin

Abstract

During times of lower global sea level, vast areas of the coastal shelf were exposed and converted into ecologically diverse coastal landscapes that wereattractive for human occupation. The landscapes were subsequently flooded during the deglaciation, but well-preserved remains of these landscapes andtheir inhabitants can today be found on the seafloor. In the southern Baltic Basin, where the complex relative shoreline displacement history exposedlarge coastal areas, many submerged landscapes can be found. However, in Swedish waters, the research interest in these landscapes has been limited.The Hanö Bay area in southeastern Sweden, where well-preserved remains of early Holocene coastal landscapes can be found off the coast at Haväng ineastern Skåne and in the near-shore waters in western Blekinge, is an exception. The overall aim of this thesis is to increase the understanding of thesecoastal landscapes, their inhabitants and the water level changes that formed, and later inundated, the landscapes.High-resolution bathymetry data, organic sediment sequences, surveillance and sampling of wood remains and archaeological artefacts by divers andGIS-based palaeogeography modelling were used in this multidisciplinary project to investigate the shoreline displacement, coastal environments andhuman resource exploitation in the Hanö Bay region during the early Holocene.Based on the depth and age of submerged rooted stumps and organic sediments from Haväng, the early Holocene shoreline displacement in the areahas been refined. The Yoldia Sea lowstand level was determined to 24–25 m b.s.l. and the subsequent Ancylus Lake transgression lasted approximately500 years, from 10,800 to 10,300 cal BP, with a mean rate of 4 cm yr -1. The maximum Ancylus Lake level was determined to about 5 m b.s.l., while thelowstand level of the subsequent Initial Littorina Sea Stage was determined to approximately 10 m b.s.l. The maximum level of the Littorina Sea Stage inthe area was determined to about 4 m a.s.l. at c. 6000 cal BP.During the Yoldia Sea and Ancylus Lake Stages, the Haväng area was a pine-dominated open woodland with a slow-flowing nutrient-rich stream characterized by ponds and wetlands. Recovered bones with slaughter marks show that aurochs and beaver were hunted in the area. During the subsequentInitial Littorina Sea Stage, the river mouth developed into a productive lagoon surrounded by a more closed forest with both coniferous and deciduoustrees. The findings of several stationary fishing constructions, dated to 9000–8400 cal BP, indicate that the subsistence was focused on large-scale fishing, which suggests a development towards a sedentary lifestyle and year-round presence in the coastal landscape. The area was finally inundated during the Littorina Sea transgression phase, at about 8000 cal BP. The preservation of the submerged landscapes and their artefacts in the Hanö Bay region is dependent on generally sheltered conditions, either by coveringorganic sediments in a river-mouth or lagoonal environment and/or little or no exposure to extreme wave activity. Even though these landscapes havesurvived for thousands of years, their future is uncertain. By introducing marine nature reserves, these valuable archives can be better protected for futuregenerations.This study shows that submerged landscapes can be excellent natural and cultural archives and that a geoarchaeological approach can maximise theresearch output, providing detailed information on shoreline displacement, landscape dynamics and coastal human societies