A miocene palaeovalley network in the Western Taurus (Turkey).
Résumé
Lower Miocene conglomerates in the Köprü and Manavgat basins contain pebbles that can be confidently traced back to their source areas, owing to their distinctive lithologies. Among others, are the green Huğlu volcanics (Late Trias), known only in allochthonous units from the Beyşehir region, or the Alanya blueschists, restricted to the Sugözü unit in the Alanya Massif. The problem is to find out how this detrital material could have travelled about eighty kilometres through the Taurus calcareous units during the Miocene. Fortunately, the present drainage system is not yet fully reorganised in the Taurus, and large areas of the chain still retain fossil morphologies. These may be seen in the upper karstic areas of the chain, where a large part of a high surface (1500-2200 m) is preserved. On this surface several dry valleys, some of them 400 m deep, with meanders and tributaries, have been recognised. They are disconnected from the present drainage, and represent fragments of a former network directed NE-SW, at right angles to the structures of the Taurus chain. The age of this network may be attributed indirectly to the Early Miocene. On the other hand, the presence of blueschist fragments in conglomerates of the Aksu Basin cannot be explained through a NE-SW-directed drainage system, and implies instead that the Alanya Massif extends to the west below the Miocene cover of the Antalya Gulf. Later, Late Miocene faulting fragmented the high surface and disrupted the drainage system. Uplift of the Taurus chain followed in the Pliocene and Quaternary, and is responsible for the extensive karstic circulation seen today, which left aside remnants of the ancient morphology of the chain.