Proceedings - Johannes Gutenberg-Universität Mainz

2 nd INQUA-IGCP-567 International Workshop on Active Tectonics, Earthquake Geology, Archaeology and Engineering, Corinth, Greece (2011)
EARTHQUAKE
ARCHAEOLOGY
INQUA PALEOSEISMOLOGY
AND ACTIVE TECTONICS
subsequently we hope to determine the earthquake
recurrence and contribute to improve hazard
estimates. We have studied 3 giant piston cores
collected during the MARMACORE Cruise in August-
Septembre 2001. The cores were taken in the
Çinarcic basin (MD01-2425), and in the Orta basin
(MD01-2429, MD01-2431), at depths between 1230
and 1170m. The sedimentary record in theses cores
represent the sedimentation of the last 20 kyr.
METHODS
One of the challenges is the distinction between finegrained,
slow and continuous, hemipelagic
sedimentation, from quite instantaneous resuspension
and re-deposition. For this we combined
different tools in order to characterize the textures:
grain size (laser diffraction grain size analyzer,
Malvern TM ), anisotropy of magnetic susceptibility
(Kappabridges MFK1-FA AGICO) and X-ray imagery
(D.G.O.’s SCOPIX). Compositions were controlled
through magnetic susceptibility (BARTINGTON TM
MS2 contact sensor), and microscopic analysis. The
chronology was established from
14 C (AMS
measurements) derived from wood, plants and
sapropelic muds. We calibrated the ages with Oxcal
Program v4.1. The ages found represent the
Holocene and part of the late Pleistocene.
RESULTS
The analyzed sections are composed of fine grained
terrigenous material (clay-silty) intercalated with siltysandy
laminated intervals, turbidites sequences and
liquefaction features as ball and pillow. The upper
marine part is predominantly compose by the claysilty
slightly calcareous and in less percentage by the
silty-sandy laminated intervals, theses intervals
consist of milimetric’s lenticular and parallel planar
beddings.
In the lower non marine part the fine grained
terrigenous material is abundant but we find
numerous turbidites sequences with thicknesses
ranging from centimeters to decimeters. This
turbidites can show erosive bases, normal gradation
and ripples, others can show an abrupt contact
separating the coarse grain basal part (bed load) of
the fine grain upper part (suspended load)(Fig.2), this
later are defined as “homogenites”. In this non
marine section we can also find in less proportion the
slumps and the levels with deformation structures
(possible seismites).
Fig.2 Textural and compositional characterization of three homogenites present in the non marine section (core MD01-2425). The
mean size, magnetic susceptibility and lineation magnetic don’t show differences between the hemipelagic normal sedimentation
and the homogeneous coseismic sedimentation. The foliation magnetic (AMS) is higher in the homogenites than the hemipelagic
deposits, this high foliation contrast has to be explained by different arrays of phyllosilicates, associate a specific settling
conditions related to water mass oscillation.
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