"Mysteriously, there was no other signs of life, such as pottery," he added.
Using microscopy, X-ray and stable isotope techniques, Andrews and colleagues analyzed the mineral content and texture of the underwater formation.
"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," Andrews said.
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The researchers speculate the distribution of such doughnut shaped concretions is likely the result of a sub-surface fault which has not fully ruptured the surface of the sea bed.
The fault allowed gases, particularly methane, to escape from depth.
"Microbes in the sediment use the carbon in methane as fuel. Microbe-driven oxidation of the methane then changes the chemistry of the sediment forming a kind of natural cement, known to geologists as concretion," Andrews said.
He noted that in this case the cement was dolomite, an unusual mineral which rarely forms in shallow seawater, but can be quite common in microbe-rich sediments.
"It is important to look carefully at underwater stonework in archaeological settings like Greece or Italy and be very sure that we look for all the evidence to prove that the archaeology is really what we think it is," Andrews told Discovery News.