Grigorii G. Akhmanov2 and John M. Woodside3


Mud volcanism on the Mediterranean Ridge has been the object of intensive investigation during Training Through Research (TTR) expeditions in 1993, 1994, and 1995 (Gelendzhik and Professor Logachev cruises). As a result, a large database has been compiled on the lithology of mud volcano deposits exposed on the seafloor.

The Ocean Drilling Program (ODP) holes that were drilled during Leg 160 within the Olimpi Area, the most studied mud diapiric area of the Mediterranean Ridge, have allowed us for the first time to look deeper into the mud volcanoes and to analyze some peculiarities of their development since the Pliocene.

The composition of buried mud breccias that were recovered during Leg 160 was found to be rather typical of the Olimpi area, as determined from the earlier TTR investigations. Significant differences between buried breccia and mud breccia exposed on the seafloor were not observed. Most of the mud breccia clast types previously described for exposed mud breccia flows of the Olimpi area were found in the ODP samples. No new types were observed in the buried and older mud breccias.

Mudstones are prevalent among rock fragments of the mud breccia samples recovered by ODP as well as in exposed Olimpi mud breccia. Micrites, fossiliferous micrites, and packed biomicrites are as widespread among lithoclasts of the limestone group as in the youngest mud breccia flows. The different sandstone fragments observed in the ODP mud breccia samples correspond to the subfeldspathic lithic wackes and lithic arenites previously described from the Olimpi area. The crystalloclasts have all resulted from disintegration of different rock fragments within the mud breccia. The set of crystalloclasts corresponds completely to component compositions of the lithoclasts. The Olimpi mud breccia matrix examined in both Leg 160 samples and TTR samples is similar and mainly composed of smectite and mixed-layered (illite/smectite with prevalent smectite layers) clay minerals (40%-65%), kaolinite (15%-30%), and illite (10%-30%). The lack of significant downhole variation in mud breccia composition suggests that the source formations for the Olimpi mud breccia have not changed since at least the late Pliocene.

Comparisons of the compositions of the Olimpi mud breccia (on the basis both of ODP and previous data) with mud breccias from other known diapiric area on the Mediterranean Ridge exhibit some differences. The differences reflect peculiarities of source formation lithology and structural tectonic setting of mud volcanoes in different areas of the Eastern Mediterranean. There are also common features of the Mediterranean mud breccia, which indicate that some common sedimentary series extend through the whole Eastern Mediterranean.

1Robertson, A.H.F., Emeis, K.-C., Richter, C., and Camerlenghi, A. (Eds.), 1998. Proc. ODP, Sci. Results, 160: College Station, TX (Ocean Drilling Program).
2Faculty of Geology, Moscow State University, Moscow, Russia.
3Correspondence author: Faculty of Earth Sciences, Free University, De Boelelaan 1085, 1081 MV Amsterdam, The Netherlands. wooj@geo.vu.nl