Underwater Shell Middens: Excavation and Remote Sensing of a Submerged Mesolithic site at Hjarnø, Denmark (Open Access Article)

New Open Access Article (Free to download)


Shell middens, or shell-matrix deposits, occur in large numbers across the coastlines of the world from the mid-Holocene (ca. 6000–5000 cal BC) onwards, often forming substantial mounds. However, they become smaller, rarer or absent as one goes back into earlier periods, suggesting a world-wide process of economic intensification. Since sea level was generally much lower during these earlier periods, a critical question is the extent to which mounded shell middens could have accumulated on now-submerged palaeoshorelines, and if so, how they were affected by the potentially destructive impact of sea-level rise. Further, and important to modern practice, it is essential that archaeologists consider how such sites can be discovered through underwater investigation. Here we offer a proof of concept that shell middens can survive submergence and can be detected, using systematic investigation of a rare example of a confirmed underwater shell midden at the Mesolithic site of Hjarnø (ca. 5300–4300 cal BC) in Denmark. We compare the excavation results with the results of geophysical survey, explore the problems of distinguishing underwater cultural shell middens from natural shell beds and conclude that shell middens can survive inundation by sea-level rise and can be detected by remote sensing, but require at least minimally invasive sampling to establish their cultural status. We suggest the methods developed may be applicable to coastal and marine sites impacted by postglacial sea-level rise worldwide.

Keywords: Mesolithic, Ertebølle, underwater archaeology, submerged landscapes, sidescan, sub-bottom profiling

From Australia to Scandinavia to the Middle East … and back again: DHSC PhD Candidate Chelsea Wiseman

As a PhD candidate on the DHSC project my research focuses on an international comparative study of submerged landscapes. I am starting with an existing knowledge of the submerged Neolithic sites off the Carmel Coast of Israel, an area I have studied for some time and on which I wrote my Honours thesis. Understanding how these sites were formed, transgressed by postglacial sea-level rise, and preserved – eventually to be found and recorded by archaeologists, will help me to complete my aim to compare these submerged sites with prospective areas in other areas around the world, including in the DHSC study area in NW Australia. In a similar way to the DHSC project’s ongoing work in Denmark, this allows us to move from a known example of submerged landscape archaeology in the Eastern Mediterranean, learn from it, and extrapolate what I can to better understand the potential in Australia.


I began my PhD in early 2018 and while it has certainly been a steep learning curve, it has also been immensely rewarding. In April 2018, I attended the meeting of the Scientific and Technical Advisory Body for the UNESCO 2001 Convention on the Protection of Underwater Cultural Heritage, held in Paris, France. I also took the minutes for the meeting of the UNESCO UNITWIN Network for Underwater Archaeology. Both meetings provided an ideal opportunity to learn more about the increasingly global community involved in underwater archaeology, and to be present for the discussions surrounding the implementation of the 2001 Convention. Amongst the subjects raised at both meetings was the upcoming Decade of Ocean Science (2021-2030), and the involvement of the underwater cultural heritage community. There is certainly potential for the contribution of submerged landscape research, with both meetings emphasising the integration of underwater cultural heritage with spatial planning, and the development of palaeoenvironmental knowledge bases.

IMG_4240.jpgIn May/June and again in September/October of last year, I assisted with a series of marine geophysical surveys conducted by the DHSC team in the Dampier Archipelago. Along with other members of the project team, I spent several weeks conducting surveys with a sidescan sonar to better understand the features at the bottom of the ocean around the Dampier Archipelago. The sidescan sonar provides high resolution imagery of the sea floor, allowing the team to analyse the seabed textures and associated features as we refine our survey strategy to analyse submerged landscapes. We’re now working through the data to search for areas which might be conducive to the preservation of archaeological material, and other noteworthy features on the seabed.

blogpostimage2.jpgAlso in 2018, I joined the DHSC team in Hjarnø, Denmark, where I assisted Francis Stankiewicz and Paul Baggaley in conducting sidescan sonar and sub-bottom profiler surveying. The data from these surveys will be analysed alongside marine sediment cores, and this combination of marine geophysics and coring provides information about how sediments developed over time, and allows us to reconstruct the past (now submerged) landscape. I was also able to join the underwater team and assist in the excavation of a submerged Mesolithic settlement. This field season marked an important milestone for me: my first dives on a submerged prehistoric site. The bulk of my undergraduate training was in terrestrial archaeology, so I learned to dive specifically to transfer my archaeological abilities to underwater prehistory. The cultural material obtained from these sites is remarkably preserved, and the knowledge to be gained from the analysis of submerged sites is critical in furthering our understanding of human interactions with the marine and coastal environment.

Wiseman_2017.jpgLast July, I travelled to Israel, where I joined a team of researchers on the Bronze and Iron Age site of Tel Dor to undertake further training in underwater archaeological methods. The Near East has an extraordinary amount of archaeological material in both the terrestrial and underwater environment, and the team at Dor aims to integrate the data from its terrestrial and underwater excavations for a rounded view of the maritime history of Dor. We also held a 2019 joint field school between Flinders University and the University of Haifa as part of the UNESCO UNITWIN Network for Underwater Archaeology.

In the past year of eclectic experiences in underwater archaeology in different parts of the world, it has become especially evident that international and interdisciplinary collaboration is key not only to my own professional development, but to undertaking well rounded and widely contextualised archaeological research. It is especially important to me as well as to the DHSC team, in our efforts to illuminate and better understand the submerged past.


DHSC’s Team of International Volunteers: Katie and Kat

Katie Woo and Katarina Jerbic are PhD students from two Australian universities. They join the DHSC core team here in Hjarnø this month to contribute to the project and to learn about submerged archaeology in a new environment. Both Kat and Katie focus their own research on past environments and their influence on prehistoric human populations. This week they undertook the task to core marine sediments at a new site in order to characterise the formation and distribution of geological and cultural sediments.


Kat finished her MA in Archaeology and Ethnology at the Faculty of Humanities and Social Sciences at the University of Zagreb, Croatia in 2009. Participation in prehistoric digs excavations throughout her university years resulted in a keen interest in prehistoric archaeology. Her MA thesis, which focussed on the prehistoric pottery of the Jačmica cave, led to an on-going position at the Archaeological Museum of Istria in Pula. That’s when she began excavating a 6000-year-old submerged prehistoric pile-dwelling settlement in Zambratija Bay in the Adriatic Sea, which resulted in her training to be a diver to help assist with the recording of the site. That led to an opportunity to undertake a PhD at Flinders University. Katarina’s contribution to this year’s fieldwork in Hjarnø was to core the seabed around the excavation trenches in order to determine the extents of the cultural layers as well as to reconstruct the past sea-level change on the site by looking at the presence of microfossils in the cultural sediment layers from the site.


Katie is an archaeomalacologist (shellfish analyst) doing her PhD at the University of Sydney.  Her research focusses on shell midden sites located in Western Arnhem Land, in the north of Australia.  She is using a combination of archaeological, ecological, and biological data to reconstruct the diets, landscape use patterns, and environmental impacts of the groups inhabiting the area throughout the Early to Mid-Holocene (9000-2000 years ago). Previous excavations in Hjarnø have uncovered a significant amount of shellfish material which relates to the Ertebølle Culture. Katie was invited to join the Deep History of Sea Country project to analyse the shellfish material, and to bring a new perspective to the study.


Their main role so far has been to collect data to reconstruct the development of the sediments in the fjord. The layers found within these cores have been described, drawn and photographed for documentation. This data will then be compared with the sub-bottom and side scan sonar data, being collected by the marine geophysicists, to reconstruct how the sediments in the fjord have been laid down over time.


Kat and Katie have been enjoying their time on the fieldwork, learning from each other as well as the rest of the team. They are looking forward to integrating their results with the rest of the team’s data to help answer questions about the submerged prehistoric past.