Carbon dating analysis
In tectonically active margins such as the Nankai and Tokai regions off Japan, dense methane hydrate reservoirs have been identified.
Cold seeps releasing methane rich hydrocarbon fluids are common here, supporting a wide variety of biological species that hold a symbiotic relationship with the chemosynthetic bacteria. bivalve colony (over 400m2 in size) was discovered off Tokai, Japan.
The measured 14C age ranged in three age groups of 1396±36-1448±34, 1912±31-1938±±34.
The 14C age of shells that were alive upon collection and the dissolved inorganic carbon (DIC) in seawater show little difference (˜100 14C age) indicating that shells are not heavily affected by the dead carbon effect from cold seeps that is of biogenic or thermogenic origin, which can make the age to become considerably older than the actual age.
It is unusual for a bivalve colony this size to mostly be dead, raising questions as to what caused their death.