Acoustic facies of Holocene megaturbidites in the Eastern Mediterranean

The acoustic facies of Holocene megaturbidites in the central-western abyssal plains of the Eastern Mediterranean Sea is analysed, combining core lithology and synthetic seismograms produced on the basis of P-wave velocity profiles derived by multi-sensor core logging (from a core in the Western Herodotous Trough). The acoustic facies of the megaturbidite is divided in two layers: (1) an upper, transparent, low velocity layer, corresponding to structureless mud; (2) a lower, highly reflective, high velocity layer, corresponding to the graded sandy base. Correlation with sub-bottom profiler data allowed us to estimate in about 21\textendash23 m the maximum total thickness of the two-layer megaturbidite in the Ionian Abyssal Plain. These results demonstrate that thicknesses traditionally computed on the basis of the acoustically transparent layer alone may produce a relevant underestimation of the total volume of the deposit. The total volume of the megaturbidite, extending over the Ionian and Sirte Abyssal Plains including the western Herodotous Trough, is therefore estimated in about 162\textpm10 km3.