Gotlands Län is simply the island Gotland, the largest island in the Baltic Sea and the largest island of Sweden. Located about 90km east of the Swedish mainland and about 130km from the Baltic States it lies more or less on the crossing of trade routes through the Baltic Sea. Inhabited since prehistoric times, source of fire stone and amber, the island became a commercial center during the Middle Ages. Todays capital, the town of Visby, was the most important Hanseatic city in the Baltic Sea. The Hanse (Hanseatic League) was a trade union of cities from northern Germany and all around the Baltic Sea. They had robust ships and installed a sort of monopoly for the trade around the Baltic sea.
Gotland consists of Silurian sedimentary rocks. A 200m to 300m thick layer of limestones and shales overlies a 75m to 125m thick Ordovician sequence. The limestones were deposited in an oxygen rich, shallow, hot and salty sea, on the edge of an equatorial continent. Reef growth started during the Llandovery, at this time the sea was about 50-100m deep, but subsequently the gound went continually down. The downlift was compensated by reef growth and sedimentation between the reefs, the water depth never exceeded 175-200m. To the end of the Ordivician the sea shallowed and bioherm detritus, and terrestrial sediments filled the basin. Some sandstones exist in the upper layers, which were deposited very close to the shore line.
Today the limestones of Gotland are karstified. A typical feature for Gotland are raukar (rauks), stone column created by erosion which often have unusual shapes. They are interpreted as karst forms or karst features.
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