イランの深海考古学アップデート

以前にもお伝えしたササン朝ペルシア時代の沈没船の調査ですが飽和潜水による発掘が提案されているようですが、イランではプロのダイバーが少ないため考古学者などを含め、専門家を呼びトレーニングなどを行うそうです。

この遺跡はシラフの港の沖で漁師が発見したものだそうです。漁師が地元の考古学者に連絡をいれ、連絡を受けた国家海洋考古学チームが調査を行ったところ遺跡の年代と重要性が確認されました。水深７０Ｍであるため普通の空気でのダイブは難しいそうです。だからといって貴重な遺跡を無視することは出来ないのでイラン政府はいろいろと計画を練っており、国際的な協力関係もありそうです。イランだけでなく、インド洋の海事考古学の発展に充分貢献できる遺跡だと期待しています。

Tehran, 9 November 2006 (CHN) — “Death Trap!” This is what archeologists call the area 70 meters below the waters of the Persian Gulf where nearly two months ago the remains of a merchant ship belonging to either of the two superpowers of Ancient Persia, namely the Parthian (248 BC – 224 AD) or Sassanid (224-651 AD) empires, were discovered. Lack of sufficient facilities has turned salvation of this Partho-Sassanid shipwreck a challenging task.

The Persian Gulf is a hot spot for oil companies whose ships continuously sweep over this body of water searching for new oil and gas resources. Nevertheless, until last September no one was aware of the existence of an ancient ship sunken in the Persian Gulf near the port of Siraf until the local fishermen got hold of an unknown giant ship below the waters. Later, the Darya-Kav-e Jonub Company (Southern Sea Investigation Co.) was commissioned by the Iranian Cultural Heritage and Tourism Organization to investigate the area. Initial studies by this company unveiled a mystery: A humongous ship and its cargo have been lying below the waters for 17 centuries.

Once the news was spread, archeologists from all over the country and abroad were excited to start excavation of the ship, not knowing of the huge obstacles ahead.

Manager of the Southern Sea Investigation Co., Zolfaqar Arabzadeh, says: “Bringing the sunken ship and its cargo out of the water is a real feat. Part of the task goes back to having enough expertise while the other part has to do with the facilities needed for this job. The ship and its cargo are at a depth of 70 meters of the Persian Gulf. Going to such depth without necessary facilities would result to death after only a few minutes. This is why we have no choice but using a technique called saturation diving which is a well-known method in diving for objects. This technique enables the diver to get deep in the sea using a combination of Oxygen, Hydrogen and Helium … Besides, taking out the cargo and the ship requires having skilled divers, but their number in Iran does not exceed a handful.”

Saturation diving is a special diving technique that allows nearly unlimited time to work underwater. It is the most efficient and efficacious method to accomplish work at ocean bottom depths. The technique allows divers to remain at great depth for long periods of time by living under pressure in special living chamber complexes affixed to a diving support vessel, oil platform or other floating work station.

“Saturation” refers to the fact that the diver’s tissues have absorbed the maximum partial pressure of gas possible for that depth due to the diver being exposed to breathing gas at that pressure for prolonged periods. This is significant because once the tissues become saturated, the time to ascend from depth, to decompress safely, will not increase with further exposure.

Commonly, saturation diving allows professional divers to live and work at depths greater than 50 meters (165 feet) for days or weeks at a time.

Only highly professional and experienced divers may carry on excavations at the depth of 70 meters where the ancient Persian shipwreck is located. However, the “Saturation Diving” method brings the risks down to a minimum. Yet this method was never used in Persia (Iran) in the past and so even the most professional divers would need some training sessions, typically four weeks long, to get familiar with this new technology.

Saturation diving is based on the principle that the pressure of the dissolved gas in the blood and tissues is the same as that of the gas in the lungs. Basically, a diver goes down to a depth, perhaps 300 feet, and remains there until no more gas can dissolve in the tissues — the tissues are saturated with nitrogen. Once the saturation point has been reached, the time required for decompression will be the same no matter how much longer the diver stays at that depth, whether it be a minute, an hour, a day or a week. This principle has been used for divers who live and work in undersea habitats.

“The importance of taking the cargo out of the water would result in the introduction of a new technique in Iran which is unique in its own special way. To this date, the technique has been used by non-Iranian divers in Iran and costs millions of dollars,” adds Arabzadeh.

The use of compressed air in diving is the method commonly practiced by Iranian divers. Such method enables the diver to dive down to a depth of 50 meters at maximum for a limited period of time. Should the same “traditional” technique be used by divers at the depth of 70 meters, a maximum of 5 minutes is all they can endure the pressure on their lungs. Staying at such depth longer than this period would exponentially raise the risk of death. Even the first five minutes is not a hundred percent safe as some believe that it could cause permanent breathing problems.

40 meters is the maximum permitted depth to which a person may dive according to world standards. A combination of helium and oxygen would be required if one wishes to go deeper down.

Captain Mehdi Masoumi, the retired first skipper of Iran’s Marine Forces who served for 28 years during his career, speaks of the challenges of the Persian Gulf shipwreck excavations: “Had this ancient ship been discovered at a depth of 40 to 50 meters, there would have been no need for sophisticated diving equipments. The need for such facilities has always been felt in Iran, especially by its Marine Force. The country’s petroleum installations which are considered vital for Iran must have become equipped with such technology long ago, but today we can see that it was never acquired. This is while the Iranian oil companies could extract oil from the depth of 80 and even 90 meters in the Persian Gulf. At present, enormous amount of money is spent by the country’s oil companies for hiring foreign divers to do the job at deeper levels. We do hope that the salvation of this shipwreck would open the gates to this system in Iran.”

How was the Partho-Sassanid shipwreck discovered?

The newly discovered ship was found by accident when local fishermen were having just another “ordinary” day. Hamid Shams, member of the board of managers of the Southern Sea Investigation Co. and one of the first people who found the mysterious ship, recalls his memory of that day: “We always work in the same area the ship was discovered. One day, a number of local fishermen announced that they fished pieces of earthenware. Since we had worked with the Cultural Heritage Organization in the past, we went to the area to make pictures. The pictures were then displayed in the underwater archeology department of Iran’s Archeology Research Center. [After examining the pictures,] the Center’s experts declared that the ship’s cargo contains big jars, known as amphora, which were in use only during the Parthian and Sassanid dynastic periods. These jars were seemingly in use for holding oil and liquids. We then showed the film we got from the shipwreck to Dr. Fazeli-Nashli, director of Iran’s Archeology Research Center, and he gave us his Organization’s support.”

According to Shams, no action was taken after that on the part of the Archeology Research Center while he believes that at least the Center could cooperate in making a higher quality film of the shipwreck.

Shams continues by saying: “We wrote a letter to Dr. Fazeli-Nashli and announced our full readiness to take part in this project. Since diving at such depth is a highly specialized concept and ICHTO is quite inexperienced in this area, we see ourselves part of this project and believe that we must do something. We even have a workshop and good facilities at Asalouyeh [an industrial region in Southern Iran close to the place where the shipwreck was found], and can host ICHTO’s experts. We can also offer them with proper facilities such as boats and diving and filming equipments which suffice for initial studies. This is a cooperative project in which we can make use of the archeologists’ experiences in the field of archeology and they take on ours in diving. On the other hand, we have good connections with a number of marine companies abroad and can use their experiences and act as a bridge between Iran and marine companies outside the country.”

Commenting on the suggestion put forward by Shams, the Manager of the Southern Sea Investigation Co. said: “We can seek help from foreign companies in this project since it is a big one. Not only are our cultural heritage experts new to underwater archeological activities, our diving companies are also unfamiliar with cultural heritage concepts. Aside from a few companies such as ours who have cooperated with the Cultural Heritage Organization in a few projects, we must also make use of the experiences and information of others who have done such projects in the world and we must be careful not to cause any harm to the ship’s cargo.”

In the meantime, the first step in bringing this Partho-Sassanid ship out of the water could be accomplished by taking out samples of the ship. This can be done using the existing facilities. However, the current facilities are by no means sufficient for continuous activities for prolonged periods at the depth of 70 meters. Even taking out small bits and pieces from such depth is a hard task which can only be achieved by few diving professionals, not exceeding 5 people in Iran.

Commenting on the lack of expertise for such mega project in Iran, Arabzadeh adds: “Facilities required for diving in the depth of 70 meters are very costly. However, it seems that this project is absolutely worth spending millions of dollars while we can not put a price on its immaterial value. Spending money for such projects is as insignificant as a drop of water when compared with the sea. When recovered, this ship will be the most exceptional one in the Persian Gulf region.”

Captain Masoumi completes Arabzadeh’s comments by saying: “People from all over the world would then come to see this ship. When similar discoveries are made in the world, the discovered object becomes internationally known; such event must also happen in Iran. On the other hand, the discovery of this ship drew in lots of international divers who volunteered to help recovering it and have a share in the thrill. The recovery of this ship could create a huge turmoil in the world.”

The most effective way in taking the ship out of the water is to make a topographic map of the ship, number each piece, and take them out one by one. The pieces would then be put together in accordance with the map in the appropriate place.

Some experts believe that the discovery of this ship which belongs to either one of the two great Persian dynasties, Parthian or Sassanid, in the Persian Gulf could be used as a proof against false claims by some neighbor countries of Iran in the dispute over the Persian Gulf, as some Arab states attribute this body of water to themselves, calling it the “Arabian Gulf!!” The newly discovered Persian Gulf shipwreck clearly shows that this waterway has always been part of Iran (former Persia) throughout the history as it was used for commercial and military purposes 2000 years ago as proved by this ship. (To read more on Persian Gulf name abuse, click here. More information about the Persian Gulf naming dispute is also available here)

First attempts to save the Partho-Sassanid ship of the Persian Gulf have already started. However, this huge project cannot be completed with the current state of technology and experience in Iran’s underwater archeology and could in fact be a dangerous adventure for the Iranian divers who want to safely carry through what they call the “death trap” since diving to that point and staying there longer than 5 minutes would for sure threaten their lives. Yet, the discovery of the ship is a merry event which could open up new arenas never explored in Iran’s underwater archeology.

引用元：http://www.payvand.com/news/06/nov/1117.html