Fluvial versus tectonic controls on the late Holocene geomorphic and sedimentary evolution of a small Mediterranean fan delta system

摘要

This note examines the relative role of fluvial and tectonic controls in the sedimentary and geomorphic evolution of the Asopos delta, a small, active-fault-bounded Mediterranean fan delta system in eastern Attica (Greece), over the late Holocene, a period of quasi-static sea level. Despite the location of the delta in the hanging wall of a major normal-fault system that ruptured in a magnitude 6.0 (Richter scale) event in 1938 and the reporting of significant local effects (including tectonic subsidence) in contemporary accounts of the earthquake, there is little evidence from sediment core analysis and archival data of any significant longer-term effect of the 1938 event on sedimentation processes and geomorphology in the fan delta. An earlier phase (pre-thirteenth century AD) of channel migration and subsequent progradation in the western part of the delta is likely to have been fluvially, rather than tectonically, controlled. Recent rates of (vertical) sediment accumulation in the delta area are extremely low (<2 mm/yr, based on 14C and 210Pb dating), consistent with sediment starvation, which may lead to loss of deltaic area under any local relative sea level rise, except in actively aggrading channel areas and their immediate surroundings.