Researchers from the University of East Anglia (UEA) and the University of Athens (UoA) have confirmed that what were believed to be remains of an underwater "lost city" were actually created by naturally occurring phenomenon stemming from microbes.
The remains, which resemble paved floors and courtyards, were speculated to be the ruins of a long lost civilization that was destroyed by tidal waves that crashed into the Greek holiday island Zakynthos. However, the new study suggests that the remains were created by a natural geological process up to five million years ago in the Pliocene era.
"The site was discovered by snorkelers and first thought to be an ancient city port, lost to the sea," said Julian Andrews of UEA and lead author of the study. "There were what superficially looked like circular column bases, and paved floors. But mysteriously no other signs of life - such as pottery."
The discovery was made close to Alikanas Bay and examined by archaeologists that conducted mineralogical and chemical analyses. Afterwards, the UoA and UEA teams conducted more comprehensive analyses including microscopy, X-ray and stable isotope techniques.
"We investigated the site, which is between two and five meters under water, and found that it is actually a natural geologically occurring phenomenon," Andrews said. "The disk and doughnut morphology, which looked a bit like circular column bases, is typical of mineralization at hydrocarbon seeps - seen both in modern seafloor and palaeo settings.
"We found that the linear distribution of these doughnut shaped concretions is likely the result of a sub-surface fault which has not fully ruptured the surface of the sea bed," he continued. "The fault allowed gases, particularly methane, to escape from depth."
Andrews suggests that microbes in the sediment drove the oxidation of methane, which they use as fuel, ultimately altering the chemistry of the sediment and creating natural cement. In the case of the remains examined in the study, the cement was dolomite, a rare occurrence in seawater.
"This kind of phenomenon is quite rare in shallow waters," he said. "Most similar discoveries tend to be many hundreds and often thousands of meters deep underwater."
"These features are proof of natural methane seeping out of rock from hydrocarbon reservoirs," he continued. "The same thing happens in the North Sea, and it is also similar to the effects of fracking, when humans essentially speed up or enhance the phenomena."
The findings were published in the May 19 issue of the journal Marine and Petroleum Geology.
