5 th International Symposium on Eastern Mediterranean Geology Thessaloniki, Greece, 14-20 April 2004 An example of geological and geomorphological heritage to be protected: Gölcük caldera (Isparta - southwestern Turkey) Somuncu M. 1 , İnaner H. 2 & Çiçek İ. 3 1,3 Ankara University, Department of Geography, 06100, Sihhiye, Ankara, Turkey, Mehmet.Somuncu@humanity.ankara.edu.tr. 2 Dokuz Eylul University, Faculty of Engineering, Department of Geology, 35100, Bornova, Izmir, Turkey, hulya.inaner@ deu.edu.tr. Keywords: lake, caldera, volcanism, tourism, education South Western Turkey is generally known as the ‘Area of Lakes’ because of the numerous lakes covering tectonically formed basins in the area like Lake Beyşehir (656 km 2 ), Lake Eğirdir (468 km 2 ), Lake Eber (126 km 2 ). Many of these lakes are quite shallow. Lake Burdur, which is 50 metres deep, is the deepest of them all. Beyşehir, which is the third largest of the country, is only 7-8 metres deep. The deepest point in Lake Eğridir is 16.5 metres. Gölcük caldera and Lake Gölcük, which covers the bottom of this caldera and is the subject of this paper, is different from all the lakes of the Area of Lakes in every respect. This lake is situated approximately 5 km to the southwest of the city Isparta. As it is different from the oth- ers in respect of its formation, it is also smaller in size from the others beyond comparison. It covers approximately an area of 0.8 km 2 at the bottom of the caldera, which has a radius of 2200 metres. The longer radius of the lake in east-west orientation is 1500 m, and north-south radius is about 850 m. It is deeper than the other lakes of the area but Lake Burdur despite its small size. The deepest point of the lake is 41 m. It is 1387 m above sea level among hills of 1500-1600 m altitude. Why should Lake Gölcük be protected? Two different types of formation can be found in the area. First of these two is a flysh facies of sub-Miocene age, and the second is a facies formed as a result of the volcanic activity in Pliocene period. The sub-Miocene flysh which forms the base in the area is made up of lime- stone, marl and sandstones (Karaman 1990). It contains recifal facies lens limestones as well (Akbulut 1980). The formation of the area was greatly influence by the tectonic activities effec- tive during mid-Miocene. As a result, numerous folds, faults and cracks of various types have developed within the formation. It has been aged as Burdigalien based on its fossil content. (Karaman 1990). While Piocene aged basement andesite rocks are found on slopes of hills like Hisar Tepe, Kara Tepe, Karakaya Tepe, trachiandesite rocks are primarily located young cones (Pilav Tepe, Sungur Tepe) within the caldera and found in dikes in the southern and western slopes of Hisar Tepe (Kuşcu and Gedikoğlu 1990). K/Ar age determination method shows that these Basement rocks are 4-4.7 years old and aged sub-Pliocene (Leferve at al 1983). Upon the volcanic basement rocks rests younger pyroclastic material with distinct layers from top to bottom. At the bottom lies a layer made up of more of andesitic tuff, lapilli, pumice, and andesite blocks. In general, it is of slackly formed layered strata, which are characterized with formations distinguished by gradations, cross-bedded layers, and load cast structures. In higher levels lie strata rich in pumice, tuff and lapilli. Although sometimes layers of pumice reach a thickness of 5 m, they are not laterally continuious. In places, cross-bedded layers can also be observed (Karaman 1990). Ref: S4-5