Ancient shipwrecks found during the 20th century were surveyed using the technology available to archaeologists at the time – and some of those techniques it turns out could be damaging. Now new capabilities are sending teams back to revisit some of those earlier maritime discoveries.
One of these is the “Kyrenia” shipwreck found off northern Cyprus, where re-examination of its timbers and cargo have enabled a more accurate dating to be made than when it was found nearly 60 years ago.
The 15m vessel, which would have had a crew of four, was discovered by local diver Andreas Cariolou back in 1965, and was the first major Greek Hellenistic-period ship to be found with a largely intact hull.
From 1967 to 1969 the wreck was excavated, raised and reassembled for scientific study, including its cargo of hundreds of amphoras, some containing thousands of green almonds.
Three Kyrenia replicas were produced and sailed, but the timeline of the ship's building and sinking had until now remained vague. The amphora designs and a small batch of coins had dated it to the later 300s BC.
PEG problem
The problem faced by modern researchers was that the original conservers had used polyethylene glycol (PEG), a standard treatment applied to preserve timbers removed from sea water in the 1960s. The resulting petroleum contamination had rendered radiocarbon-dating impossible.
So a team led by Prof Sturt Munning of Cornell University’s College of Arts & Sciences in New York worked with researchers at the Netherlands’ University of Groningen to find a way of cleaning 99.9% of PEG out of wood. They tried it out successfully on Roman-era samples from Colchester that could be tree-ring-dated to check that the method worked.
The Cornell Tree-Ring Laboratory has now examined cleaned-up timber samples from the Kyrenia wreck using the latest in modelling and radiocarbon dating techniques and, as a result, has narrowed the sinking down to the 25 years between 296 and 271BC, with a strong probability that it occurred in the six years between 286 and 272BC – a more recent date than the earlier estimates.
The Kyrenia timbers were found to have grown in the mid-late-4th century BC. Because the samples did not include bark, the researchers could not pinpoint when the trees were felled, but reckon this was likely to have been after 355-291BC.
Resetting the curve
Another problem arose when the revised dating for the wreck failed to align with the “international radiocarbon calibration curve”. This is based on known-age tree-rings and used to convert radiocarbon measurements into Northern Hemisphere calendar dates.
Manning’s team was able to identify a flaw that had arisen years ago in this curve as a result of a period of inadequate information, and have been able to revise it. This they say will be of significant benefit to the scientific community in future studies.
To help in narrowing down the Kyrenia dates as far as possible, the researchers also focused on organic materials found on the wreck, including a sheep or goat ankle-bone probably used for games or divining rituals, and the thousands of green almonds onboard. Like the timbers, these were radiocarbon-dated.
The study, which has just been published in PLoS ONE, also includes work by researchers from the Oxford Dendrochronology Laboratory and the University of California, Irvine.
Also on Divernet: ANCIENT HARBOUR IS NEW DRAW IN CYPRUS, ROMAN SHIPWRECK FOUND OFF CYPRUS, CYPRUS IMPOUNDED OTTOMAN WRECK FINDS, WRECK SITE IDENTIFIED IN CYPRUS
