Kukersite is a marine type oil shale of Ordovician age, found in the Baltic Oil Shale Basin in Estonia and North-West Russia. It was named after Kukruse settlement in Estonia in 1917 by Russian paleobotanist Mikhail Zalessky. The kukersite deposit in Estonia is one of the world’s highest-grade oil shale deposits with more than 40% organic content and 66% conversion ratio into shale oil and gas. Oil yields of kukersite are 30 to 47% of the shale by weight. Most of the kerogen is derived from the fossil green alga, Gloeocapsomorpha prisca, which has affinities to the modern cyanobacterium, Entophysalis major, an extant species that forms algal mats in intertidal to very shallow subtidal waters.
Kukersite in Estonia occurs as an often calcareous layer of 2.5–3 metres thickness. Along the coast the Kukersite lies near the surface and dips to the south, so that the deposits is found at depths from 7 to 100 m.
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