Mudanya formasyonunun sedimantolojisi: Gilbert turu yelpaze delta gelisimini kontrol eden depolanma olaylari (Orta-Gec Miyosen, Marmara Denizi guneyi)

This study was performed to investigated the depositional characteristics of the Miocene siliciclastic sediments in Mudanya Basin. In this study, volumetricly, the most abundant siliciclastic sediments in the studied region are named as Mudanya formation. This formation unconformably lies on a unit known as Tastepe basalt around the district of Mudanya and its thickness and lateral community increase towards the south. It is laterally and vertically covered by the white lacustrine limestones in the vicinity of Bursa-Karacabey highway. Mudanya formation consists of two members, namely the Adatepe and Koy members on the basis of their physical characteristics. Vertical facies change of Miocene siliciclastic sediments were deteremined through three measured stratigraphic sections. According to these measurements, debris flow process (lithofacies A), meandering river process (lithofacies B) and processes of stream discharging into lake (lithofacies C) were identified. Subaerial and aerial portions of the siliciclastics involved by the Mudanya formation with fan delta character, were determined by facies analyses. Lithofacies A and B form the aerial portion (alluvial fan), while the lithofacies C forms the subaerial portion of the fan delta. It was observed that the lithofacies B with meandering river character, occurs repeatedly four times in the measured sections. It was concluded that the erosional interrelationship of each subfacies B, resulted from the channel migration arising from the paleoclimatologic changes during the Middle Miocene. The measurements carried out in the planar cross-bedded sandstones of the Mudanya formation indicated that the general direction of the paleocurrent in the Middle-Late Miocene was from ENE towards WSW. The Mudanya formation in lateral and vertical transition with the Camlik formation which consists in turn, of white, laminated lacustrine limestone. This situation shows that the Koy member of the Mudanya formation had been deposited in a large system of lakes. The Mudanya fan delta, deposited during the Middle-Late Miocene, indicates that its alluvial member has been localy deposited in a large system of lakes. These fan delta shows the characteristics of a Gilbert type delta that has been fed from a point in an alluvial fan, and more affected due to its own inertia in a system of lakes having steep shore slopes.