This data set is part of a larger data harmonization effort to make lake sediment core data machine readable and comparable. Here we standardized organic carbon data of sediment core PG2135, retrieved in 2013 from Lake Ulakhan Chabyda (Yakutia, Russia) at 1.7 m water depth. The thermokarst lake Ulakhan Chabyda is in an exorheic basin in the coniferous forest area and has one outflow and several small inflows. It lies at an elevation of ca. 195 m a.s.l. with a surface area of ca. 2.1 km2 and a maximum lake water depth of estimated 2.1 m. The 6.51 m sediment core was retrieved by a Russian peat corer during the RU-Land_2013_Yakutia expedition of the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI, Germany, Potsdam) in cooperation with the North Eastern Federal State University (NEFU, Russia, Yakutsk). Total carbon and total nitrogen contents were quantified using a Vario EL III carbon–nitrogen–sulphur (CNS) analyser. Organic carbon was measured with a Vario MAX C analyser.