Research of activity periods of the active Aigion Fault (Corinth Gulf, Greece) pointed out by the palaeo-environmental study of Holocene and Upper Pleistocene deposits
by
Francis Lemeille
Institut de Protection et de Sûreté Nucléaire (IPSN), BP6 92265 Fontenay-aux-Roses France
Coauthors: C. Bourdillon (Emergence Incubateur du Maine, Le Mans France), C. Guernet (Univ. Paris 6, France), D. Sorel (Univ. Paris Sud, France), M. Manakou (Univ. Thessalonique, Greece), C. Berge-Thierry (IPSN, France), S. Leroy (Brunel Univ., London, UK)

The 205 m-long borehole G1, dedicated to the fitting of a deep accelerometer and to geomechanical experiments and geophysical measurements, has been carried out on the south rim of the Corinth Gulf (Greece) in the framework of the CORSEIS European Program. It is located nearby the Aigion Fault in the hanging wall of the fault close to the present shoreline. This fault, involved in the 1995 earthquake (M = 6.2), belongs to a present active faults system in one of the most seismic area in Europe. From the bottom to the top, the borehole is crossing Upper Pleistocene and Holocene deposits alternating marine, brackish and continental facies spreading from MIS 5a (ca 78 ka) to Present.

The goal is to point out anomalies in sedimentation rates, in subsidence rates and in marine excursions which could be related to seismic events.

Various studies are undertaken on samples from the borehole for improving the knowledge of environmental changes (malacofauna, ostracodes, benthic and planctonic foraminifers, diatoma, nannoplancton, pollen, dinokysts, d18O, sedimentation parameters, dating, …). The geological survey and the continuous sampling provide palaeoenvironmental data (salinity, temperature, energy, oxygenation, water thickness, location vs. shoreline, trophism, freshwater irruptions). These results will be compared to data obtained from other methods (palaeoseismological trenches, U/Th cement fault datings, offset of marine terraces on each side of the fault) which also provide fault activity periods. The research of tsunami facies is also carried out in the borehole.

Date received: February 18, 2002