Charting the past: surveys map two lost harbors of Phoenicia.

By analyzing long tubes of sediment drilled from locations in and around the Mediterranean ports of Tyre and Sidon, scientists have discovered the locations of the harbors from which legions of ancient Phoenician mariners set sail.

Tyre and Sidon, located in what is now Lebanon, were the two most important city-states of Phoenicia, a trading empire founded more than 3,000 years ago. Although archaeologists knew much about the two cities and Phoenician civilization, they have long debated the sizes and locations of the ancient harbors, says Christophe Morhange, a geoarchaeologist at the National Center for Scientific Research in Aix-en-Provence, France. Now, Morhange and his colleagues present strong evidence to settle the dispute.

The researchers drilled 25 holes within the modern city of Sidon and 30 within Tyre, recovering a sediment core at least to meters long from each site. From the contents of those samples, representing the past 8,000 years, the team determined the locations and extents of the ancient harbors. And by carbon-dating the plants, wood, and shells in the harbor samples, the researchers pegged the period when the ports were active. Morhange and his colleagues report their findings in the January Geology.

Both harbors started out as natural bays before the cities were built, says Morhange. The shells and remains of marine organisms found in the oldest sediments are characteristic of sheltered waters. While large ships could have anchored in the bays when the cities were young, their cargo would probably have been ferried to shore in small boats.

About 1200 B.C., the Phoenicians began building artificial harbors to shelter their fleets and to accommodate their expanding trade network, Morhange proposes. Protective structures calmed the waters, and fine-grained sediments accumulated.

Although Tyre and Sidon gained their fame and splendor during the Phoenician era, the ports were most active in the GrecoRoman and Byzantine periods, from about 330 B.C. until A.D. 1000. The large amounts of fine sands and mud deposited during this interval hint that the harbors were almost fully enclosed, says Morhange. The Romans dredged some areas to maintain sufficient depth for ships.

With the demise of the ports during medieval times, a more open marine environment returned. Then, over time, the harbors became clogged with silt. Later, the city centers of modern Tyre and Sidon were built upon material that accumulated after the cities' fortunes waned.

Although the ancient cities were considered important, archaeologists had few other details, says Dorit Sivan, a coastal geologist at the University of Haifa in Israel. The sediment record is sometimes better than the archaeological one because cities often are destroyed and then rebuilt, she notes.

The team's findings "solve a centuries-old mystery of where these harbors actually were" says David E. Fastovsky, a geoscientist at the University of Rhode Island in Kingston.