The Santorini volcanic complex and its relation to the stratigraphy and structure of the Aegean arc, Greece

Abstract

The Santorini complex is the most active volcano of the southern Aegean volcanic arc. Its relationship to the surrounding area was examined by using a dense set of seismic reflection profiles. Three seismic units were recognized in the surrounding area. Unit A consists of generally strong subparallel continuous reflectors, into which two subunits A1 and A2 were distinguished, that are unconformable in the upper slopes and the shelves and conformable at lower sectors. The age of unit A, which consists mainly of volcaniclastic sediments, is considered Quaternary. Unit B consists of faulted and slightly folded strong continuous reflectors that pinch out at lower basin margin sectors than unit A. Its age is mainly Pliocene, its sediments are probably terrigenous, and it was deposited in the basins at the early and middle stages of their formation. Finally unit C represents the acoustic (mainly metamorphic) basement. The dominant tectonic structure in the area is the NE-SW trending normal faults, superimposed on earlier E-W normal faults. The Santorini complex includes one caldera at Santorini and one crater at Columbus about 7 km to the northeast. The caldera of Santorini consists of four deep basins (depth from 290 to 390 m). The Columbus volcano has a well defined crater with a single basin (depth ~ 500 m) and was formed in 1650 A.D. by an underwater explosion. The start of volcanic activity of Santorini, which initiated in the Early Pleistocene and continues up until today, may be related to the change in the normal fault orientation from E-W to NE-SW, and to the unconformity between units A and B.