ABSTRACT

The southern Aegean Sea is a present-day forearc basin characterized by an outer arc of strongly uplifted, older, deformed rocks. Since the time of its formation, it was split by extensional tectonic movements into several basins in which different sedimentary sequences developed. The study of sand-size turbiditic sediments from the basins reveals two main compositional sand suites (plus a third group of sediments showing aberrant compositions derived from the mixing of the other two): 1) quartzolithic sand suite derived from the outer arc; and 2) lithovolcanic suite derived from the volcanic arc of the Cyclades. The suites develop separately in the different basins depending on the control exercised by the tectonics of the source areas and the physiography of the basins. Quartzolithi sands occur mostly in the outer basins, close to the outer arc, whereas lithovolcanic sands occur in the central part, where deposition of terrigenous quartzolithic sediments is small. Volcanic-derived sediments are mostly wind-blown ashes first deposited on the edges of the basins and then redeposited by turbidity currents. Transport of sediments occurs mainly longitudinally to the basins along tectonically controlled canyons. There is a direct correlation between these sand suites and the small-scale tectonic setting of the source area. However, because of the anomalous presence of an ancient orogenic belt such as the outer arc, a quartzolithic sand suite can develop in the forearc basin, representing an exception to current ideas on the relationship between plate tectonics and sand c mposition. This exception is due to the diffference between the actual tectonic setting in the southern Aegean Sea and the oversimplified models.