Rapid Holocene Evolution and Neotectonics of the Albanian Adriatic Coastline

Abstract

High-resolution 1986 Landsat TM images of the Adriatic coast of Albania have been compared with aerial photographs obtained in 1943, and published literature, in order to decipher the sedimentary architecture and evolution of the late-Holocene deposits of the coastal plain. This coastline is microtidal and dominated by wave action; and abundant sediment is supplied by rivers draining the uplifted mountainous interior of this tectonically active region. The coastal plain has prograded up to 40 km since relative sea level rise slowed down around 6000 years BP. The inland parts of the coastal plain are dominated by parallel storm beach ridges whilst the coastal fringe exhibits a diversity of symmetrical to asymmetrical wave-dominated deltas and spit-deltas encompassing cut-off lagoons. A genetic model to explain the variability of wave-dominated deltas on the Albanian coast is proposed showing a spectrum of forms between prograding symmetrical cuspate deltas formed by bi-directional longshore drift and highly asymmetrical spit deltas formed by uni-directional longshore drift. Avulsive switching causes abandonment; the symmetrical forms become smoothed out by wave action whereas the spit-deltas become detached barrier beaches that migrate onshore by washover, welding themselves onto the coast. The back barrier cut-off lagoons in this setting have a very low preservation potential.

Two much larger lagoons, now partly reclaimed, at Karavasta and Narta, lie within the belt of beach ridges; both have a straight seaward margin parallel to known post-Neogene faulting. The lagoons exhibit differential subsidence which is regarded as neotectonic in origin; the presence of a 60 km long graben or half graben structure linking the two areas of subsidence is suggested to explain the observed phenomena. Subsidence up to 5-10 m is indicated within the last 1,000- 2,000 years.