Geology versus myth: the Holocene evolution of the Sybaris Plain

Abstract

Historical accounts handed down the legend of the ancient Sybaris, defeated and submerged by the Crotoniates who diverted the River Crati on the town. This paper deals with the reconstruction of the Holocene evolution of the Sybaris Plain, through a number of geological and geomorphological observations. In particular, I found i) ∼1 m/yr horizontal coastal progradation rate since Greek times (2.4 kyr BP), possibly since Neolithic (7.0 kyr BP), mainly originated by active alluvial deposition and subordinately by regional uplift; ii) evidence of striking modifications in the surface hydrography of the plain during the last 2.5 kyr, with repeated fluvial captures of the Crati and Coscile rivers testified by ancient historians and geographers, recent maps and archeological accounts. In addition, datings and archeological information from 7 sites in the plain provided iii) ∼0.6 mm/yr mean uplift rate during the past 11.2 kyr, that confirms the substantial continuity of this regional process with upper Pleistocene; iv) local, high value of subsidence (0.5÷2.0 mm/yr) affecting the Sybaris main archeological area. Subsidence is not recorded before 4000 years BP and is caused by deposition of fine, highly compressible sediments at the transition between marine and continental environment; v) no evidence of a fault-induced contribution to the subsidence, whilst there is the grounded possibility that man-induced subsidence prevailed in the last century; vi) widespread active continental deposition in the area. Local rates of deposition are relatively lower (1.5 mm/yr) at sites where subsidence is not observed, and range between 2.5 mm/yr and 3.5 mm/yr in the main archeological area. There is also evidence of a clear decrease of the sedimentation following the Mid-Holocene flex of the fast trend of sea level rise. These data suggest that the Holocene evolution of the Sybaris Plain is due to the progressive eastward migration of the land-sea boundary, probably active since the Mid-Holocene (∼7.0 ka). Repeated floodings, regional uplift and relative sea-level changes produced the eastward expansion of the plain, subsidence locally slowed it down. Therefore, geology first allowed the creation of Sybaris, then caused its destruction.