Lipid biomarkers in sediments of mud volcanoes from the Sorokin Trough, NE Black Sea: Probable source strata for the erupted material

Abstract

Mud volcanoes (MVs) are formed by expulsion due to lateral or vertical compression of overpressured fluids in the sub-surface. Their sediments are characterized by a specific lithology called mud breccia, which is composed of inorganic and organic matter sourced from different sedimentary units and transported from the sub-surface to the seafloor. Biomarker lipid distributions were determined for sediment cores collected from the Kazakov, NIOZ and Odessa MVs in the Sorokin Trough, northeastern Black Sea. This revealed different mud breccia sources that are directly linked to the location of the fracture zones or diapiric folds formed by tectonic compression. The Kazakov MV shows biomarker characteristics of relatively mature organic matter, likely related to the Maycopian Shale Formation. The NIOZ and Odessa MVs contain immature organic matter derived from much shallower sediments overpressed by rising Maycopian diapirs. In the mud breccia from the NIOZ MV, biomarkers clearly record two different mud eruption episodes reflected in distinct distributions from unrelated sedimentary facies. Hence, the study shows that, although the organic matter of a mud breccia is sourced from a complex mixture of lithofacies, the collective biomarker signal reveals specific signatures of the sedimentary sections that contributed most to the migrated fluid.