GEOMORPHOLOGICAL STUDY OF AN AREA WITH MUD DIAPIRS SOUTH OF CRETE (MEDITERRANEAN RIDGE)

During Meteor Cruise 25/4 in 1993, a multibeam bathymetric (Hydrosweep ) survey was carried out on the Mediterranean Ridge in an area south o f Crete (comprising the original Olimpi and Prometheus-a mud diapir fi elds). The morphology is characterized by subcircular (domes) and elon gated (ridges) features. The studied area is subdivided from west to e ast in three relief provinces with predominance of the domes in the mi ddle one. We suggest that all the domes are related to mud diapirism ( as is proved for some of them by sonographic surveys and already publi shed sediment cores). The orientation of the relief elements (domes an d ridges) corresponds to that of the large morphotectonic features: Th e NW-SE orientation (Hellenic Trench) prevails in the western province , the NE-SW orientation (Ptolemy, Pliny and Strabo Trenches) is domina nt in the eastern province. The domes occur in the middle province whe re both orientations influence jointly the morphotectonic pattern on t he Mediterranean Ridge. The concentration of the mud diapirs is inferr ed to be due to crossing fault systems which may have led to an enhanc ement of conduits for ascending mud breccias and fluids. The high-reso lving sonographic records of a W-E running survey displayed a detailed anatomy of mud domes/volcanoes with features of broad variation of ba ckscatter intensities such as how lobes and streams, circular elevatio ns (mini-domes) and depressions (pockmarks) of small and smallest scal e. As a very characteristic feature not described before, in the areas outside the mud domes an extensive network-like pattern of small high -backscatter lineations has been observed which is tentatively interpr eted as a system of fractures (joints) of near-surface Mg-calcite crus ts. Their orientations were found to correspond to the regional morpho tectonic pattern.