Julian Andrews, a geochemist at the University of East Anglia in England and the lead author of a paper in the journal Marine and Petroleum Geology about the work, said that the area was a “cold seep” where methane in deep formations moved upward through faults and then through sediments in the seabed. Those sediments contain bacteria that consume methane for energy.

All that consumption of methane, Dr. Andrews said, changed the chemistry of the seawater that saturated the sediments. That caused dissolved minerals to precipitate out of the water as a rock called dolomite. And the dolomite cemented the sediment particles in place, forming concretions. The columns and other shapes resulted from the methane spreading in different ways through the sediments as it flowed upward.

Dr. Andrews said the researchers’ analysis suggested that the concretization might have occurred several million years ago deeper in the sediments and that the objects had been exposed over time as the seabed eroded.