Sokolov authored reference works on the stratigraphy of Eastern Europe, in particular the fossil coral records, and created the concept of Vendian period, currently recognized as largely overlapping, but not fully equivalent to Ediacaran.
Sokolov's early work concentrated on the stratigraphy of the Russian Platform, in particular the diagnostics of fossil corals for the identification of Carboniferous period deposits.
[2] Shortly before the outbreak of World War II Sokolov was appointed to lead a Soviet field research company in China.
Together with Vladimir Saks (1911–1979) Sokolov created a new Siberian school of stratigraphy and paleontology, which survived into the 21st century as the Institute of Oil and Gas Geology.
Sokolov continued production of geological references, but eventually concentrated on his theory of the transition from Vendian (Ediacaran) biota to Cambrian, which he believed was critical to our understanding of evolution.