Archaeologists investigating Fiji’s Vanua Levu have identified a small coastal island whose sediments are made up largely of discarded shellfish remains. The site, near Culasawani on the island’s north coast, covers about 3,000 square metres and contains a shell-rich deposit that makes up 70 to 90 per cent of its material. Radiocarbon dates from 10 shell samples cluster around 1,190 calibrated years ago, with a median date of about 760 CE. Researchers believe the formation may be a ‘midden island’, created through repeated shellfish processing and disposal, although they have not ruled out the possibility that the deposit was produced by a powerful wave.
What did archaeologists find on Fiji’s 1,200-year-old shellfish island
According to the study published in Nature, titled ‘Shell-Dense Island Off Culasawani, Vanua Levu Island, Fiji: Midden or Muddle?’, the shell deposit is between 20 and 40 centimetres thick and contains remains from numerous edible species. Researchers identified Anadara antiquata, Gafrarium tumidum and Codakia tigerina principally, alongside species of Asaphis, Atactodea and Nerita. Gastropods Trochus niloticus and Turbo species were recorded. None of the examined shells showed visible evidence that they had been deliberately manipulated to remove the meat.The researchers also found small fragments of plain pottery within the shell deposit. These fragments were recovered both on the surface and below it, including material from cores and excavation pits. Their presence indicates that the pottery was probably contemporary with the shell deposit. No comparable concentration of other archaeological material, such as fish bones or stone tools, was identified during the fieldwork.
PC: Study: Shell-Dense Island Off Culasawani, Vanua Levu Island, Fiji: Midden or Muddle?
Ten shell samples reveal the island’s age
To establish the age of the shell deposits, researchers excavated four 1-by-1-metre test pits and obtained 10 Anadara shell samples for radiocarbon dating. The dates were closely clustered rather than being spread across a long sequence. Taken together, they produced a median age of about 1,190 calibrated years before present, corresponding to approximately 760 CE, with a calibrated range of 1,530 to 910 years before present, or roughly 420 to 1040 CE.The concentration of dates was important because it provided evidence about how the shell-rich deposit formed. The study states that the narrow age range, combined with the nature of the shellfish remains, supports the interpretation that the deposit has a relatively homogeneous origin. The researchers therefore favour the possibility that people accumulated the shells during a period of intensive occupation or processing around 1,190 calibrated years ago.
Ancient people may have built the shellfish island
The site represents a ‘midden island’ land created as people repeatedly discarded large quantities of shellfish remains in one location. According to the researchers, early post-Lapita settlers may have lived at or near the site around 1,190 calibrated years ago and processed substantial quantities of edible shellfish over several centuries. The discarded shells could have accumulated vertically while relative sea level changed, eventually producing an area of shell-rich land that stood above the surrounding water.The location was primarily used for processing rather than permanent settlement. The absence of stone tools and animal bones, together with the abundance of edible shellfish and pottery fragments, is consistent with a specialised processing area. The researchers suggest that people could have processed shellfish close to where they collected them, placed the edible flesh in pots and transported it elsewhere for consumption.
Researchers favour a human-made shellfish island over a tsunami origin
The researchers have not completely ruled out a natural origin for the shell deposit. One alternative is that a powerful wave, potentially a tsunami, could have disturbed an older shell bed or midden on the sea floor and transported shell fragments across the area. The lack of visible stratification and the relatively thin shell-rich layer initially made a wave-deposited origin possible.However, the study found features that did not fit this explanation as well. If a wave had deposited the shells, the researchers expected the material to extend beyond the modern island and become progressively thinner away from the shoreline. Instead, the shell-rich layer appeared confined to the island, with no consistent changes in thickness. The fact that the remains were all from edible species also favoured a human-related explanation. The authors therefore describe the midden-island interpretation as the preferred one, while acknowledging that the natural-deposit possibility cannot be completely excluded.
Archaeologists plan more surveys around Vanua Levu
Researchers intend to search the adjoining Culasawani mainland for contemporary settlement sites, survey the nearby creek mouth and offshore area for other shell-rich deposits, and investigate local oral traditions for memories of major waves. The study notes that these investigations could help establish whether the shell island was connected to a nearby settlement and whether a major wave event affected the area.If the interpretation is confirmed, the Culasawani site would be the first described midden island in the tropical Pacific east of the Bismarck Archipelago in Papua New Guinea, according to the researchers. The study also highlights that Vanua Levu, despite being Fiji’s second-largest island, has received comparatively less archaeological attention than other parts of the archipelago.
