Classification of mud volcanoes in the South Caspian Basin, offshore Azerbaijan

Abstract

A 2D seismic grid in the South Caspian Basin, offshore Azerbaijan, is used to define the areal distribution of mud volcanoes and to make a classification of the mud volcanoes based on characteristic seismic features. A high concentration of mud volcanoes is observed at the southern part of the study area that coincides with the distribution of subsurface structures within the basin. Mud volcanoes with low relief (several tens of meters) are concentrated primarily in the northeastern portion of the study area; mud volcanoes with large vertical relief (greater than 200 m) are clustered in the southwest part of the basin. Mud volcano development in the South Caspian Basin is generally linked to faults, which in some instances are detached at the basement level. The seismic database allows us to determine the relative timing of mud flows and gives us valuable information about mechanisms of mud volcanism within the South Caspian Basin. The cycles of mud volcano activity coincides with time of high sedimentation rates, regional contraction episode and a major stage for hydrocarbon generation. Mud volcano formation within the South Caspian Basin is primarily controlled by compressional tectonic forces and overpressured sediments. Mud volcano activity may not always be related to the Maykop organic rich shale succession (Late Oligocene–Lower Miocene) but may also occur at shallower stratigraphic zones.