Palaeoclimatic evolution during Eocene and its influence on oil shale mineralisation, Fushun basin, China

The Fushun basin is a small, explored, coal and oil shale-bearing, Cenozoic fault basin in the Liaoning Province, northeast China. The basin mainly consists of Eocene swamp to lacustrine deposits of the Guchengzi to Xilutian Formation, and contains the biggest opencast oil shale mine in Asia. This mine has provided an ideal opportunity to undertake palaeoclimate reconstruction in this basin based on a single geological profile and the analyses of 93 samples, using various approaches, namely field geological observation, clay mineralogical and geochemical (Sr/Ba, Sr/Cu, stable C and O isotope) analyses, all of which were compared with palaeobotanical data. The Eocene climate of Fushun basin evolved from warm temperate to north subtropical, and generally changed from warm humid to subhumid–semiarid. Paleoclimatic and geochemical parameters shows that the very warm and humid climate during Jijuntun Formation increased the initial productivity of lake water, and caused a steady stratification of the lake water, then caused oxygen lack in the bottom of water. Productivity of the lake provides the mean origin of organic matters for oil shale formation, and steady anoxic environment is beneficial for the conservation of organic matters.

► Eocene climate of Fushun basin evolved from warm humid to subhumid–semiarid.
► Warm humid climate during Jijuntun Formation increased the initial lake productivity.
► It also caused a steady lake stratification and oxygen lack in the bottom.
► Lake productivity provides the mean origin of organic matters for oil shale formation.
► Steady anoxic environment is beneficial for the conservation of organic matters.