DRAINAGE DEVELOPMENT AND SEDIMENT SUPPLY WITHIN RIFTS, EXAMPLES FROM THE SPERCHIOS BASIN, CENTRAL GREECE

Drainage systems juxtaposed with modern depositional environments within the Sperchios rift allow detailed analysis of the relationships between drainage catchments, sediment supply and alluvial fan/fan delta geometries. Prominent footwall escarpments within the rift are created by E-W-trending normal faults, and variations in the topography of these escarpments are related to fault segmentation and bedrock lithology. Drainage catchments within the rift are classified on the basis of morphology, area, bedrock lithology and relationship to fault geometries. Five drainage domains can be identified within the Sperchios rift: (i) footwall, (ii) hanging wall, (iii) transfer zone, (iv) axial and (v) karst domains. Bedrock lithology has a major control on the size of catchments in all drainage domains. In addition, topographic lows associated with transfer zones along the border fault are sites of major drainage catchments and act as conduits for sediment supply to the rift. Variations in drainage catchments, the resultant sediment supply and accommodation development along the rift produce a range of stratigraphic architectures. Along fault segments, low sediment supply and high subsidence rates lead to aggradational sequence sets, whereas progradational sequence sets develop at transfer zones where rates of sedimentation are high and the rate of subsidence is low.