Ivrindi-Balikesir, Nw Anatolia
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International Symposium on Geography Environment and Culture in the Mediterranean Region GEOMORPHOLOGY OF THE UPPER PART OF KOCAÇAY RIVER BASIN, (İVR İND İ-BALIKES İR, NW ANATOLIA) Kamile GÜLÜM 1 Abstract Study area: the upper watershed of Kocaçay river-basin is located on the south of the Marmara Region. It covers an area of 751 km². Policyclic topografic forms are dominant since different tectonic and climatic process have affected the study area. The land forms of the study area are closely related to the lithological properties. Dominant topographic shapes are plateaus as they are dissected by running water. Although the dominating topographical features today show a mature type of topography, valleys are generally younger. Drainage systems have mostly been formed during the Pliocene Age . It has been developed in the Quaternary. In fact, the valley system is of the Plio-Quaternary period. The topographical discordance found in the study area is probably the result of Post-Alpine tectonical uplift that occurred at the end of the Pliocene Age and the beginning of the Quaternary. There are three erosional surfaces at an elevation of 550-750 meters, 300-520 meters, and 210-300 meters. These surfaces indicate different erosional and depositional process to have occured in the study area. In other words, tectonic movements are responsible for the formation of erosional and depositional surface. Erosional activities continue in the river valley since the base level is lowered or backward. As a result, the erosion process continues. Valleys are still in the character of young valleys. In fact, when the topography in the upper track of Kocaçay river basin is considered as a whole, one can say that the development is still in the young stage. Key words: Gemorphology, Kocaçay, superimpose valley Introduction The Upper part of the Kocaçay Rivershed, which is handled as the research area, is located in the Southern Marmara Region in the northwest of Turkey. The research area neighbours with the Manyas Plain in the north, Balıkesir Plain in the east, Sava ştepe Plateau in the southeast, Madra Mount in the southwest, Edremit Plain in the west, and Şap Mount in the northwest. The area, which is blocked by the mountains in the northwest and southwest, extends towards the southeast and southwest. The Madra River (Kocaçay), which is formed through the plains on the base of the valley and plateaus with the altitude of 300-850 m, is the dominant element of the research area. The highest point in this area is Maya Hill(1344 m) on Madra Mountain and the lowest point of this area is İvrindi Plain (200 m). In the fields where the South Marmara climate is dominant, the vegetation is made of the poor forests constituted of the bushes and cluster pines and oak trees in the low altitudes. In contrast, in the high altitudes where the humidity increases with the altitude on Madra Mountain and Şapda ğ, there are robust forests consisting of black pine trees and chestnut formations. The vegetation has been destroyed over the years in a large extent. The forests exist in the south-southeast and north-northwest areas. There are various kinds of soil in the research area. In general, the dominant soil is zonal soil. But there are also azonal soils made on the alluvial and colluvial deposits. The 1 University of Adıyaman International Symposium on Geography Environment and Culture in the Mediterranean Region kinds of soil that dominantly exist in the area are red soils, brown soils, and Mediterranean soils. These soils lack lime and calcium as do the forest brown soils. The population is dense in on the plains. On the contrary, the population is scarce in the sloping ares in the south and and the areas covered with forests in the southwest and northwest. Figure 1: Location map of study area Some problems emerging from the physical, human living, and economical features of the research area cause applied geomorphologic problems. While the sloping, destruction of vegetation, and climate features (heavy rains, etc.) cause erosion around the plains, the rivers in the plains with less sloping overflow. Because these fields are alluvial fields which are rich in underground waters they increase the earthquake intensity. In the fields where the valleys are common and the sloping values are high, there have been eroded fields through lithologic characters. Geology Paleozoik terrain, which is composed of mainly limestone, covers most of the mountainous areas leading in the southern part of the area. Mesozoic terrain is associated with sedimentary rocks such as conglomera and sandstone and Kozak granitic pluton. Terrary: clayev limestone, sand stone and volcanic tuffs, andesites form terriary formation. Quaterner is prepresented with the alluvial materials. Geologic Evaluation of the Area The western part of the Anatolia was exposed to an extensional regime during the neotectonic period. In that period, some part of the study area was uplifted and depressed along some of the fault lines so the tectonic basin was formed in which detritic material accumulated. The study area is located between the Kaz Mountain and the low-land southern part of the Marmara Region. During the Mediterranne Period the vertical tectonic movements led to the hors-graben system. Namely, the gulf of Edremit and the low land of Marmara region fits International Symposium on Geography Environment and Culture in the Mediterranean Region to grabens and Kaz Mountain is the main horst area which abruptly rises in the northern part of the Edremit Gulf. During the Miocene Period, the study area covering the eastern part of the Kaz Mountain was exposed to erosion due to lake levels occupying the lowland areas and as a result neogene erosional surfaces developed. At the end of the Neogene Period, the study area again uplifted. Consequently, the river set up on the neogene erosional surfaces cut its own valley. In other words, the uplifting of the area has caused the rejumation of fluvial erosion. As a result, dissected erosional surfaces have been converted into plateaus in appearence. Geomorphological Units The research area which has the characteristics of a plateau is composed of strong rocks and a bit higher than the level of plateaus are categorized under the name of “ High Lands and Mountains.” Apart from the high lands and mountains, it is also possible to divide and classify the plateaus which take the widest part of the research area in terms of the characteristic features and different structures and lithologic elements. It is even possible to divide them into smaller categories classifying them under the name of “ Flat and Rough Plateau Surfaces.” On the contrary, all the plains and alluvial base flat places that have come into being as a result of the cavity in plateau have not been taken into the “ Flat and Rough Plateau Surfces” because of the collectivity of the morphological unit. They have been classified and explained under the headline of “ Plains and Base Flats.” Although the upper line of the Kocaçay Valley seems to have a rough and high topography, it is characterized with the plateaus which take up a large field in the research area and a flattened and monotonous topography. However, in general, the area draws attention with diversity of the geomorphologic forms that it includes. Figure 2: A picture of Madra Valley International Symposium on Geography Environment and Culture in the Mediterranean Region Figure 3: Geologic map of the study area Figure 4: Geomorphologic units of the study area International Symposium on Geography Environment and Culture in the Mediterranean Region Hiıgh Lands and Mountains This part in the southwest of the research area includes Madra, Kozgeçit, Çetin, Mısırtarlası and Haydar streams and the watershed. They are the highest points of the Madra Mountains. It reaches 1343 m in Maya Hill. There is a high land in İkizce, Kılcılar, and Büyükyenice villages where the altitudes of the Madra Mountains decrease, which is called Asar Tepe (816 m). The highest point is Mount Sabla whose altitudes decrease from Madra Mountain which is 1110 m high. Göldede Hill (871 m),which is located on an old volcanic cone on the northeast part of the mountainous land, stretches through Madra Stream (Kocaçay) and Yahu Stream. Havran Stream flows into the Aegean Sea and the Kocaçay flows into the Marmara Sea by means of Manyas Lake and Susurluk Stream. Mount Madra combines with Mount Sap which is a part of the Kaz Mountains Range by means of a bridge of 550 m length from the north. This bridge which includes the highway between Balıkesir and Edremit separates the Aegean Basin and Marmara Basin. Göktepe (937 m) is an important rough place that is a range of Şap Mountain towards the east. Plateaus Gümeli Plateau The Gümeli plateau, which is in the south-west of the research area, is situated between Mount Madra in the south and the İvrindi Plateau in the north. The Gümeli Plateau covers a minor place in comparison with the İvrindi Plateau. However, its average altitude level is higher than that of the İvrindi Plateau. In terms of the crack of the surface, Gümeli Plateau has a considerable value over the other. It makes a high and dominant relief in the north parts of Mount Madra from which the Kocaçay River originates. The Gümeli Plateau is blocked from the east by the Kurucu Mountain range. Faults, which have a considerable effect on the formation, also have a great role in shaping the topographic characters of the Gümeli Plateau. İvrindi Plateau The İvrindi Plateau is the second biggest plateau that lies between the “Main Geomorphologic Units” in the research area. The southern part of the plateau is blocked by the Kurucu mountains and Kocaçay Valley.