Sedimentation and tectonic geomorphology adjacent to major active and inactive normal faults, southern Greece

Abstract

The active Psatha–Skinos normal fault is uplifting a contrasting variety of lithologies in its footwall, including Mesozoic limestones, ophiolitic peridotites and poorly-consolidated Plio-Pleistocene sediments of the inactive Megara basin. In the latter basin, linear marginal uplands border the sedimentary fill and are interpreted as degraded and segmented scarp lines which exhibit features such as facetted spurs. Drainage domains are defined as groups of drainage basins sharing a common tectono-geological substrate. Contrasting domains in the footwall of the active fault have given rise to spectacular differences in drainage basin growth and form. In the uplifting footwall, raised coastal terrace levels are present at about 10 and 40 m. The latter have yielded corals dated at between 90–126 Ka, and have enabled us to calculate uplift and erosional rates. Extrapolation of these rates indicate that some 350 m of footwall relief has been produced over approximately 1 Ma. Most of the sediment eroded from the uplifting footwall is presumed to have been re-sedimented into the Alkyonides Gulf basin plain during this time. The prominent footwall unconformity so-produced forms a fine modern analogue to features seen in ancient syn-rift tilt blocks such as the Viking Graben. Footwall uplift has also backtilted the former depositional surface of the Megara Basin and caused reversal of flow in its axial drainage domain. A variety of depositional environments are documented in the subsiding hangingwall to the coastal fault, including syn-quake talus cones, alluvial fans, intra-fan marshes and swamps, truncated fans, transgressive barriers and spits.