Geomorphological study of an area with mud diapirs south of Crete (Mediterranean Ridge)

Abstract

During Meteor Cruise 25 4 in 1993, a multibeam bathymetric (Hydrosweep) survey was carried out on the Mediterranean Ridge in an area south of Crete (comprising the original Olimpi and Prometheus-2 mud diapir fields). The morphology is characterized by subcircular (domes) and elongated (ridges) features. The studied area is subdivided from west to east in three relief provinces with predominance of the domes in the middle one. We suggest that all the domes are related to mud diapirism (as is proved for some of them by sonographic surveys and already published sediment cores). The orientation of the relief elements (domes and ridges) corresponds to that of the large morphotectonic features: The NW-SE orientation (Hellenic Trench) prevails in the western province, the NE-SW orientation (Ptolemy, Pliny and Strabo Trenches) is dominant in the eastern province. The domes occur in the middle province where both orientations influence jointly the morphotectonic pattern on the Mediterranean Ridge. The concentration of the mud diapirs is inferred to be due to crossing fault systems which may have led to an enhancement of conduits for ascending mud breccias and fluids. The high-resolving sonographic records of a W-E running survey displayed a detailed anatomy of mud domes/volcanoes with features of broad variation of backscatter intensities such as flow lobes and streams, circular elevations (mini-domes) and depressions (pockmarks) of small and smallest scale. 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 interpreted as a system of fractures (joints) of near-surface Mg-calcite crusts. Their orientations were found to correspond to the regional morphotectonic pattern.