New evidence of extensive active mud volcanism in the Anaximander mountains (Eastern Mediterranean): The “ATHINA” mud volcano

A 3000 km² multibeam survey was carried out on the eastern Anaximander Mountains (Mts), (Eastern Mediterranean). The objective was to obtain detailed bathymetry of known mud volcanoes and identify new sites of active mud volcanism in the area. N-NW of the Amsterdam Mud-Volcano (MV) several mounds and cone-like morphological irregularities with a height of few tens of meters to about one hundred meters were detected and considered as potential MVs on the basis of their distinctive backscattered character. A group of two mounds was selected, the northern mound was sampled, documented as active, and named accordingly Athina MV. These new findings strongly support the presence of extensive active mud volcanism in the Anaximander Mountains especially in the area north of the Amsterdam MV.GEM     

Reconsideration of the structural relationship between the Parnassus–Ghiona and Vardoussia geotectonic zones in central Greece

The relationship between the geotectonic zones of the Hellenides orogen is important for understanding its geological evolution. The Parnassus–Ghiona geotectonic zone in central Greece has long been interpreted as thrust over the Vardoussia subzone. On the basis of detailed geological mapping, supported by a stratigraphic study and tectonic observations, no evidence of an overthrust of the Ghiona limestones on the Vardoussia flysch was found. The new data show that the transition of the Ghiona limestones to the Vardoussia flysch is a sedimentary passage and at certain places the base of the flysch is marked by a basal conglomerate formation. The entire deformation of the Ghiona is related to a large-scale anticline of the limestone series, presenting a highly inclined western limb, overlain by the flysch strata, which were deposited in a common basin between Ghiona and Vardoussia mountains. Consequently, questions concerning the geotectonic position of the Vardoussia subzone and the role of the Parnassus–Ghiona zone to the orogenic evolution of the eastern External Hellenides are raised.     

Mud volcanoes and gas hydrates in the Anaximander mountains (Eastern Mediterranean Sea)

Detailed multibeam, sedimentological, and geophysical surveys provide ample new data to confirm that the Anaximander Mountains (Eastern Mediterranean) are an important area for active mud volcanism and gas hydrate formation. More than 3000 km of multibeam track length was acquired during two recent missions and 80 gravity and box cores were recovered. Morphology and backscatter data of the study area have better resolution than previous surveys, and very detailed morphology maps have been made of the known targeted mud volcanoes (Amsterdam, Kazan and Kula), especially the Amsterdam “crater” and the related mud breccia flows. Gas hydrates collected repeatedly from a large area of Amsterdam mud volcano at a sub-bottom depth of around 0.3–1.5 m resemble compacted snow and have a rather flaky form. New gas hydrate sites were found at Amsterdam mud volcano, including the mud flow sloping off to the south. Gas hydrates sampled for the first time at Kazan mud volcano are dispersed throughout the core samples deeper than 0.3 m and display a ‘rice’-like appearance. Relative chronology and AMS dating of interbedded pelagic sediments (Late Holocene hemipelagic, sapropel layer S1 and ash layers) within the mud flows indicate that successive eruptions of Kula mud volcano have a periodicity of about 5–10 kyrs. New mud volcanoes identified on the basis of multibeam backscatter intensity were sampled, documented as active and named “Athina” and “Thessaloniki”. Gas hydrates were sampled also in Thessaloniki mud volcano, the shallowest (1264 m) among all the active Mediterranean sites, at the boundary of the gas hydrate stability zone. Biostratigraphical analyses of mud breccia clasts indicated that the source of the subsurface sedimentary sequences consists of Late Cretaceous limestones, Paleocene siliciclastic rocks, Eocene biogenic limestones and Miocene mudstones. Rough estimations of the total capacity of the Anaximander mud volcanoes in methane gas are 2.56–6.40 km³.