Late Neolithic Mondsee Culture in Austria: living on lakes and living with flood risk?

Abstract

Neolithic and Bronze Age lake dwellings in the European Alps became recently protected under the UNESCO World Heritage. However, only little is known about the cultural history of the related pre-historic communities, their adaptation strategies to environmental changes and particularly about the almost synchronous decline of many of these settlements around the transition from the Late Neolithic to the Early Bronze Age. For example, there is an ongoing debate whether the abandonment of Late Neolithic lake dwellings at Lake Mondsee (Upper Austria) was caused by unfavourable climate conditions or a single catastrophic event. Within the varved sediments of Lake Mondsee, we investigated the occurrence of intercalated detrital layers from major floods and debris flows to unravel extreme surface runoff recurrence during the Neolithic settlement period. A combination of detailed sediment microfacies analysis and μXRF element scanning allows distinguishing debris flow and flood deposits. A total of 60 flood and 12 debris flow event layers was detected between 7000 and 4000 varve years (vyr) BP. Compared to the centennial- to millennial-scale average, a period of increased runoff event frequency can be identified between 5900 and 4450 vyr BP. Enhanced flood frequency is accompanied by predominantly siliciclastic sediment supply between ca. 5500 and 5000 vyr BP and enhanced dolomitic sediment supply between 4900 and 4500 vyr BP. A change in the location and the construction technique of the Neolithic lake dwellings at Lake Mondsee can be observed during the period of higher flood frequency. While lake dwellings of the first settlement period (ca. 5800–5250 cal. yr BP) were constructed directly on the wetlands, later constructions (ca. 5400–4700 cal. yr BP) were built on piles upon the water, possibly indicating an adaptation to either increased flood risk or a general increase of the lake level. However, our results also indicate that other than climatic factors (e.g. socio-economic changes) must have influenced the decline of the Mondsee Culture because flood activity generally decreased since 4450 vyr BP, but no new lake dwellings have been established thereafter

Evidence for higher-than-average air temperatures after the 8.2 ka event provided by a Central European δ18O record

“…The age model for the Holocene part of the 2005 Mondsee composite sediment core (0e1129 cm composite core depth), whose sediments are composed of biochemical calcite varves with frequently intercalated detrital flood layers (Lauterbach et al, 2011;Swierczynski et al, 2012Swierczynski et al, , 2013aSwierczynski et al, , 2013b, was established through microscopic varve counting on large-scale petrographic thin sections (Lauterbach et al, 2011). This included continuous varve counting in the distinctly laminated upper part of the composite sediment core (0e~610 cm composite core depth), whereas a varve-based sedimentation rate chronology was established for the lower part of the Holocene sediment succession (~610e1129 cm composite core depth) because varve preservation in this interval was often not sufficient to allow continuous counting with reasonable error estimates over larger intervals.…”

“If worse comes to worst, my neighbors come first”: social identity as a collective resilience factor in areas threatened by sea floods

“…There is archeological evidence for strategies of collectively navigating the stressor of floods by adapting settlement structures to the given environmental situation and the needs of the group. For example Swierczynski et al (2013) report on changes in Neolithic settlements, located at the Mondsee in the Alps. There, inhabitants collectively changed their settlement pattern from "dwellings on the wetlands […] to constructing lake dwellings on piles upon the water" in order to cope with increased flood risk from the lake around 5400-4700 cal.…”

“…There, inhabitants collectively changed their settlement pattern from "dwellings on the wetlands […] to constructing lake dwellings on piles upon the water" in order to cope with increased flood risk from the lake around 5400-4700 cal. yr. BP (Swierczynski et al 2013(Swierczynski et al , p. 1610. Hence, archeology fuses well with the social identity theory and collective resilience processes which are assessed using each discipline's methods of analysis.…”

Sunken landscapes and settlement areas. On the reconquest of underwater archaeological sites

“…The lakes offered favourable, but also challenging, sites for building on their shores. As the highly complex stratigraphies of many sites show, constantly changing water levels, floods and debris flows resulted in a dynamic settlement environment even in prehistoric times, which probably resulted in a constant coming and going of people and nature (Swiecinsky et al 2013). After the disappearance of the lake dwellings on lake shores in the first millennium BC, when the water level rose steadily and village ruins sank under thick layers of lake marl, aquatic plants and animals reclaimed the shallow water zones.…”