From Oysters to Cockles at Hjarnø Sund: Environmental and Subsistence Changes at a Danish Mesolithic Site

Abstract

Archaeological fieldwork at Hjarnø Sund in Horsens Fjord (eastern Jutland, Denmark) has explored an eroding Mesolithic shell midden. Its stratigraphy is characterized by two layers, containing marine mollusk taxa typically collected by Mesolithic hunter-gatherers for food. In the field, the lower layer appeared to be dominated by oysters (Ostrea edulis), while the upper one by cockles (Cerastoderma edule), which was confirmed by our zooarchaeological study. Accelerator mass spectrometry radiocarbon (AMS 14C) dating on shells and paired charcoal samples from the two layers indicate that these are chronologically consecutive (separated by as little as 0–163 yr [95.4%]) and that the oyster-to-cockle shift dated between ~5500–5300 and ~5300–5200 cal BC (around or just after the Kongemose/Ertebølle transition). The shell midden at Hjarnø Sund is, thus, one of the oldest-known in Denmark, demonstrating that intensive shellfish exploitation was a hallmark of the Ertebølle culture from its inception. Oyster-to-cockle shifts, thus, also occurred at times other than the Mesolithic–Neolithic Transition and may have been ultimately caused by local shoreline displacements, resulting from changes in sedimentation, possibly induced by drops in relative sea level.

The Kalvestene: A reevaluation of the ship settings on the Danish island of Hjarnø

“…Situated just off the coast of Jutland, the small island of Hjarnø's location has many natural and strategic advantages (Figure 1). While the water offers a barrier to attack, Hjarnø is still close to mainland resources (Larsen et al 2018;Astrup et al 2020). It also guards the entrance to Horsens Fjord and the port connected with the medieval trading center at Horsens (Kelmelis and Pedersen 2019).…”

Underwater Shell Middens: Excavation and Remote Sensing of a Submerged Mesolithic site at Hjarnø, Denmark

“…3 (Bronk Ramsey 2009). Shell samples were calibrated using the Marine13 calibration dataset (Reimer et al 2013), with a DR of 236 ± 54 (after Larsen et al 2018). Charcoal and bone samples were calibrated with the IntCal13 calibration dataset (Reimer et al 2013 Underwater Shell Middens flint knapping activities took place directly on the shell-midden surface.…”

“…Almost all layers contain faunal remains, hazelnuts, and charcoal. The marine mollusc remains are almost exclusively typical edible species, such as Ostrea edulis, Cerastoderma edule, Littorina littorea, and Mytilus edulis (Larsen et al 2018). Both marine and terrestrial fauna are represented (see Table B in Supplementary Material), and fish bones are especially numerous, particularly cod and flatfish, occurring in concentrations that suggest the use of specific areas of the midden for fish processing (see also Andersen 1989:26).…”

“…Evidence in support of a cultural interpretation of the Hjarnø shell deposit is as follows. First, the narrow range of taxa recovered in the midden refers almost exclusively to those that were typically collected by Danish Mesolithic hunter-gatherers, such as Ostrea edulis, Cerastoderma edule, Littorina littorea, and Mytilus edulis (Larsen et al 2018). Larsen et al (2018) further noted that the shells are almost exclusively of adult specimens, are never paired as is typically the case in natural shell beds, and that epizootic infestations are present only on the outer surfaces of the shells, which is common on living shells, and not post-mortem infestations of the inner surfaces, something which is often observed in natural death assemblages.…”

The Nekselø Fish Weir and Marine Reservoir Effect in Neolithization Period Denmark

“…Both are based on a marine mollusk shell (Ostrea edulis) and a charcoal, respectively. In these cases, the age difference between the marine and the terrestrial sample is 410 ± 69 and 327 ± 70 14 C years (Larsen et al 2018). Since both terrestrial samples derive from hazel wood (Corylus sp.)…”