Mariinsk is a town in Kemerovo Oblast, Russia, where the Trans-Siberian Railway crosses the Kiya River, 180 kilometers northeast of Kemerov…Mariinsk is a town in Kemerovo Oblast, Russia, where the Trans-Siberian Railway crosses the Kiya River, 180 kilometers northeast of Kemerovo, the administrative center of the oblast. Population: 40,526 ; 42,977 ; 40,956 ; 39,700.