Photo/Illutration The survey of Tsuzuraozaki ruins in Lake Biwako used this underwater scanner model to map out the lakebed. (Provided by © Windy Network Ltd.)

OTSU—A nearly intact pottery vessel believed to be over 10,000 years old was discovered near the Tsuzuraozaki underwater ruins in Lake Biwako, the Shiga prefectural government said Nov. 25.

The vessel, with a pointed base and around 25 centimeters tall, was found at a depth of 64 meters.

Based on its shape and what appears to be engraved patterns, the survey group identified it as either Jinguji-style or Konami Upper-layer style pottery.

Estimates date it to between 11,000 and 10,500 years ago—an early phase of the Jomon Pottery Culture Period (14500 B.C.-1000 B.C.), making it the oldest artifact discovered at this site.

Commissioned by the Nara National Research Institute for Cultural Properties, the prefecture collaborated with other organizations and used a state-of-the-art underwater scanner to create a 3-D layout of the murky lakebed in October.

“This survey obtained data comparable to what could be gathered by human divers, even at deep-water sites,” said Yoshifumi Ikeda, a professor of underwater archaeology at Kokugakuin University.

The researchers adopted a system originally designed for submarine cable inspections. They relied on the scanner’s four cameras to help visualize the natural terrain and any artifacts in waters over 30 meters deep--a challenging depth for human divers.

The study took place in waters 30 to 50 meters south of the lake’s ruins. In total, the survey covered an area of about 200 meters east to west, and 40 meters north to south.

Video footage at the Lake Biwako site showed six Haji pottery jars about 1,500 years old from the middle of the Kofun Period, which spanned the third to seventh centuries.

Haji pottery is characterized as red-brown and plain.

The six jars sit arranged in a 144-square-meter area near the latest vessel found but are thought to be over 8,000 years apart in age.

Most artifacts excavated from land ruins are in damaged condition. Finding nearly intact pottery is considered more likely at underwater sites, but such endeavors have been difficult.

The latest technique could help researchers study underwater ruins across the country.

“Without relying on large submersible research vessels, we can expect significant progress in underwater archaeological investigations, especially in calm inland seas and lakes,” Ikeda said.

There are nearly 400 underwater archaeological sites nationwide. The Tsuzuraozaki lakebed site was discovered in 1924 when Jomon pottery was caught in bottom trawl fishing nets.

Since then, about 200 pieces of pottery from the Jomon period to the Heian Period (794-1185) have been found through fishing and other means. However, because the ruins lie on a deep lakebed, their full extent is unknown.

Theories about the origin of the site include pottery washing out from nearby land, ritual or funerary practices, abandonment or disposal, land subsidence caused by an earthquake, and shipwrecks or accidents. But none has been confirmed.

UNDERWATER ADVANTAGE

Another expert familiar with Lake Biwako’s underwater ruins weighed in.

“It is almost impossible for pottery over 10,000 years old to remain nearly intact in ruins on land. This is truly a discovery unique to underwater archaeology,” said Kenichi Yano, a specially appointed professor of archaeology at Ritsumeikan University.

He said the survey’s method was a noteworthy advancement.

“Also, because Jomon pottery pieces found at this site were caught in bottom trawl nets, finding this new vessel in its original position on the lakebed is significant,” he said.

Yano explained that this archaeological site lies on a valley-like formation of the lakebed at depths exceeding 80 meters. Continual subsidence caused by crustal movements, combined with the fact that the valley was not filled with sediment, is believed to have allowed artifacts to remain exposed on the lakebed for a long time.

“The latest discovery is expected to contribute to understanding the origins of the site and the geological structure of the surrounding area,” he said.

(This article was written by Yasuji Nagai and Makoto Takada.)

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