Having completed my Masters in Maritime Archaeology at Flinders in 2009, I began as a PhD candidate for the Deep History of Sea Country project in March of this year. In between, I’ve been working in cultural heritage management in my home country of Canada, with occasional forays into research-based digs in Europe. My particular interest is to study the formation, degradation, and erosion of archaeological features that have been subjected to one or more episodes of sea-level transgression. Understanding the effects of these phenomena will help allow us to identify archaeological features during underwater investigations in Australia.
I am in Denmark to help excavate a transgressed shell midden on the island of Hjarnø, and to study whether analyses of associated lithic materials could aid in that interpretation. Denmark is known for its approximately 500 shell middens from the Mesolithic period, and about the same number from the Neolithic. During the week prior to our excavation I visited some of the documented shell midden sites throughout Jutland in an attempt to get an idea of how these massive archaeological features might react to transgression. Of course, I also found time to visit the incredible Moesgaard Museum, for a side trip to Silkeborg to view the famous Tollund Man, and to visit numerous ship burials. There is so much amazing archaeology in Denmark, and a great place to study shell middens!
My time on Hjarnø has included many tasks. In addition to the excavation of a transgressed shell midden, I’ve been involved with using sidescan sonar for identifying underwater sediments and geology, collecting core samples for more detailed sediment assessment, the seemingly endless collection of photos for building photogrammetry models, geological observations of eroding cliff faces, and archaeological surveys of beach areas.
We’re going to finish our work on Hjarnø in the next few days, but look forward to our return next year. I’ve decided to stay in Denmark for an extra week though in order to immerse myself in the archaeological library at Mosegaard Museum. Our colleagues at Moesgaard have also invited me to participate in the excavation of a submerged log-boat, dated to around the same time period as the formation of many of the shell middens I’ve been studying.
From time-to-time, our Project Blog will feature guest posts from specific team members or project partners. Our first of such posts comes from Professor Geoff Bailey of the University of York (UK) and Flinders University of South Australia (and the senior member of the DHSC project leadership).
DHSC project team guest blog post: Prof. Geoff Bailey
For someone who has spent half a lifetime looking at shell middens and shell mounds in many parts of the world, and in recent years has attempted to find underwater examples offshore of known shell mounds on land, so far without success, this week on the Danish island of Hjarnø has introduced me to my first experience of a genuine submerged shell midden deposit.
The first sign of the underwater midden from land is an intertidal zone exposed at low tide and littered with flint artefacts and shells. The location is close inshore in shallow water on the edge of a channel, between the island and the mainland just 600 m away. This is exactly the sort of location expected according to Anders Fischer’s fishing site model. The sceptic in me wonders if the intertidal material has been eroded downslope from a mound that once stood on the ridge behind the modern beach. My Danish archaeological colleague Peter Moe Astrup, who first excavated the site seven years ago, assures me that this is material from the surface of a submerged midden just 20 metres further out under water. Some of this shell deposit is protected under a layer of peat and sand, but some has become exposed. It is material from here that has been gently washed ashore by tidal currents. Since the excavation of the submerged shell midden revealed an in situ hearth in the shell deposit, and bones of fish and land mammals and artefacts of flint, bone and antler typical of the classic Ertebølle, I am persuaded that the underwater deposit must be a pre-inundation in situ deposit.
The site itself is some 20 metres further out in shallow water scarcely more than a metre deep, so it is quite easy to inspect the surface of the site visible on the seabed. The shell midden layer shows large oysters, cockles and mussels, typical of shells collected for food, shell fragments and a dense litter of flint artefacts, mostly with fresh and unpatinated surfaces. But here’s another surprise. There are also large numbers of large shells of species not present in the prehistoric midden – razor shells and a species of large, thin-shelled clam. Moreover, some of the cockle shells are clearly of modern animals. This becomes apparent when I pick up a large cockle with the pair of valves intact and shut – not unknown in archaeological middens – only to find, after prising the valves apart, a live animal inside. So, the surface of the ancient midden is a mixture of modern and ancient shells from very different periods of time – in short, our familiar friend a palimpsest. Telling the modern shells that have died naturally from the prehistoric ones collected as food is not at all easy, and would be even less so when coming across a shell deposit elsewhere on the seabed with no prior knowledge. The gjytta layers are even more interesting. Peter points out a half-buried antler axe, fishes up a neatly cut segment of round hazel wood, and casually asks me to watch out for a sandbag that is protecting a partly emerged wooden log boat. What wouldn’t I give to find evidence like this in any of the other parts of the world where I have worked? Yet here in Denmark it is a struggle to get sufficient funding to do justice to the recovery of this remarkable material.
Another first for me is that I was persuaded to don a dry suit to go into the water and take a closer look. For the uninitiated like me, a wet suit lets some water through to keep a thin layer of warming water against the skin. A dry suit keeps you and your underclothes completely dry, or at any rate it is supposed to. Since I’m borrowing somebody else’s dry suit, I discover that I’ll have to take off some of my ordinary day clothes to struggle inside this rubbery ‘onesie’ garment, immediately risking the sacrifice of warmth for access. This is Denmark in early summer, much like home in England – cold, wet and windy most of the time with occasional spells of blue sky and bursts of sun. The rubber seal at the holds my throat in a near strangulating grip. I am given a safety brief on how to recover if I fall underwater and all the buoyant air in the suit goes to the feet. Not for the first time, I wonder what I am letting myself in for in taking part in an underwater archaeological project. Once in the water and submerged up to my chest, I hold a stake attached to a guideline for the best part of an hour while John McCarthy holds the other end 50 m away and keeps an eye on my progress. Jonathan Benjamin swims over the seabed with a snorkel and a camera to create a map of the seabed surface. I find myself continuously fighting to keep my footing against the power of the waves and the wind as I move the stake to the next point on the grid. But I know, as a conventional land-based archaeologist, that I cannot begin to understand what is involved in underwater work without participating in this way.
Much of the first few days have been like any other field project – trying out equipment to discover what’s missing or doesn’t work, adapting to local conditions, and working out by trial and error the best way to do things. For an underwater project, these uncertainties are amplified by the added logistical complexities associated with boats, underwater equipment and the vagaries of changing weather, tidal currents, wind and waves. A first spell of survey with a sidescan sonar on a small boat is aborted because the rain sets in and the laptop supplied with the equipment is not a waterproof model, the battery charger on one of the underwater video cameras is playing up, and a first attempt at underwater video photography over the site area has to be abandoned because of poor visibility. The drone has been damaged in transit and needs to be looked at by the nearest service agent. Civilisation in the form of wifi and other vital supplies lies on the mainland a short ferry-ride away.
Next day we try again but have to wait for the tide to change. Much time is spent standing around waiting for conditions to improve, but the time is not entirely wasted – we talk about the finer points of archaeological modelling and the purpose of archaeological theory. Later in the day we get a parking ticket on a shopping trip to the nearest town because we couldn’t read the regulations in Danish, and one of the rooms where we are staying has sprung a leak in the ceiling after a burst of heavy rain.
By day three, things are beginning to settle down, some sort of daily rhythm is becoming established, new data is coming in and getting processed, and everyone in our small team is getting on with a sense of purpose with what needs to be done.
The moral of this short saga is a familiar one for anyone used to archaeological fieldwork in unfamiliar locations. Expect that anything that can go wrong will go wrong. Be prepared. And above all be patient!
Professor Geoff Bailey is Anniversary Professor of Archaeology (Emeritus) at the University of York, UK and a Senior Research Fellow at Flinders University, South Australia. He is an expert in human exploitation of shellfish, coastal prehistory and the archaeology of submerged landscapes. He also cooks a mean chicken curry.
Archaeological excavations in a remote island cave off northwest Australia reveal incredible details of the early use by people of the continent’s now-submerged coast.
Out latest study reveals that at lower sea levels, this island was used as a hunting shelter between about 50,000 and 30,000 years ago, and then as a residential base for family groups by 8,000 years ago.
As the dates for the first Aboriginal arrival in Australia are pushed back further and further, it is becoming clear how innovative the original colonists must have been.
The earliest known archaeological sites so far reported are found in inland Australia, such as Warratyi rock shelter in the Flinders Ranges and Madjedbebe in Arnhem Land. These places are a long way from the sea, and were once even more so when past sea levels were lower and the coast even more distant.
But we do know that the earliest Australians were originally seafarers. They came from island southeast Asia and no matter which route they followed had to make sea crossings of up to 90km to get here.
The earliest landfall on the continent is now likely to be at least 50m below the present ocean. Until now we have known very little about these first coastal peoples.
For the past five years an international team of 30 scientists has been working in collaboration with the Buurabalayji Thalanyji Aboriginal Corporation and Kuruma Marthudunera Aboriginal Corporation on Boodie Cave, a deep limestone cave on the remote Barrow Island, off the Western Australia coast.
Since the initial early dates for Boodie Cave were reported in 2015, our team has been forensically analysing the archaeological and palaeoenvironmental remains, as well as re-dating the site to build up a robust picture of the lives of the people who lived here.
These dates make Boodie Cave one of the earliest known locations in the settlement of Australia and the earliest site anywhere near the coast.
When Boodie Cave was first occupied, Barrow Island was part of the mainland, with the shoreline between 10km and 20km further west.
The shoreline became even more distant as the planet moved into an ice age and sea levels dropped to 125m below present, around 20,000 years ago. Shortly thereafter global temperatures warmed and, as the ice melted, sea levels rose quickly.
Throughout this long period people returned again and again to Boodie Cave. The limestone that forms the cave provides ideal conditions for preservation, giving us incredible details about the people who lived there.
The cave contains one of Australia’s longest dietary records. These animal remains provide us with profound insights into what people were hunting and collecting from initial settlement onwards, and how they adapted to a new and ever-changing arid landscape.
Besides wallabies, kangaroos and other terrestrial animals, the archaeological deposits contain marine shells transported from the distant coast.
In the deepest levels, when the shoreline was 20km or so distant, there are only four different types of shellfish that we have directly radiocarbon dated to 42,300 years ago. These shells represent the first direct evidence of marine resource use in Australia, and some of the earliest in our region.
With rising sea levels the coastline came closer to the cave and the number and variety of marine resources increased exponentially.
By 8,000 years ago, there are 40 different types of marine shells as well as exceptionally well-preserved remains of sea urchin, mud crab, reef fish, marine turtle, marine mammal and a variety of small and medium-sized terrestrial animals.
By 6,800 years ago the cave and the whole island was abandoned as rising sea levels finally cut it off from the mainland.
We argue that Boodie Cave was used as an inland hunting shelter between about 50,000 and 30,000 years ago before becoming a residential base for family groups by 8,000 years ago.
Dietary remains in addition to shell artefacts, incised shells, shell beads and thousands of stone artefacts show that Boodie Cave was a frequently visited location on the landscape.
Our study clearly shows that not only were Aboriginal people continuing to use marine resources across a period of dramatic environmental change, but they were also exploiting a range of desert resources. This demonstrates a successful adaptation to both the coasts and deserts of northern Australia.
Recent genetic studies suggest that colonisation was coastal, with people rapidly moving around the east and west coasts of Australia before meeting up in modern South Australia.
But the coasts along which the earliest Australians traversed were very different to today’s, not only in terms of ecology but also in distance. In some places the earlier coastline would have been hundreds of kilometres from its present position.
Sea levels rise
Over the past 20,000 years sea level has risen 125m, submerging the continental shelves surrounding Australia and separating the mainland from New Guinea and Tasmania.
Our findings provide a unique window into the now-drowned Northwest Shelf of Australia.
Boodie Cave provides the earliest evidence for coastal living in Australia and gives us an indication that coastal resources have been important to people since initial colonisation.
Nearly one-third of Australia’s landmass was drowned after the last ice age and along with it evidence for coastal use by some of the earliest Australians.
Thousands of archaeological sites have been recorded on the continental shelves of Europe, Asia and the Americas, but no submerged prehistoric sites have been reported anywhere off Australia.
These submerged landscapes of Australia open up an entirely new frontier of archaeological research and will shed even further light on the lives of the first people to arrive on Australian shores.
Deep History of Sea Country: Climate Sea level and Culture
Funded by Australian Research Council (Discovery Project DP170100812)
Submerged landscape archaeology is an under-researched field in Australia and represents a major opportunity to address knowledge gaps in world prehistory such as early human migrations, the archaeology of land bridges and coastal-hinterland cultural exchange.