V. A. ZHAMOYDA, D. V. RYABCHUK, M. A. SPIRIDONOV,
A. G. GRIGORIEV, N. V. PIMENOV, A. V. AMANTOV, YU. P. KROPACHEV, I. A. NEEVIN

GEOLOGICAL AND GEOMORPHOLOGIC CONDITIONS OF POCK-MARK FORMATION IN THE EASTERN GULF OF FINLAND

In 2009–2012 new data concerning distribution of pock-marks in the eastern Gulf of Finland as well as geological and geomorphologic conditions of their formation were gathered within the monitoring of geological environments. Pock-marks of the different genesis are widespread in the gulf bottom. The pock-marks discovered within the areas of silty-clayey sedimentation in the central part of the gulf were formed as a result of biogenic gas-seepage. In the Kopora Bay pock-marks were probably formed as a result of groundwater discharge from the Vendian aquifer system, although it is possible to find some spatial correlation with tectonic faults distribution. The presence of pock-marks of several generations indicates pulsating nature of their occurrence.

Keywords: pock-mark, gas-bearing sediments, Gulf of Finland.