The Early Cretaceous coal-bearing series in the Fuxin coalfield consists of the Shahai and Haizhou Formations, in ascending order; these units contain many tens of minable coal seams that are several to tens of meters in thickness. This area is one of the largest fields containing high-quality coal in northeastern China. Lower members of the Shahai Formation and some coal-bearing members of the Haizhou Formation contain the newly discovered Fuxin molluscan fauna.

The Fuxin molluscan fauna provides new evidence concerning the presently debated age of the coal-bearing series. This fauna has been found in northern China, eastern Asia, North America, and western Europe, and is extensively associated with coal-bearing, continental lake and marsh facies. The Fuxin molluscan fauna provides a reliable clue for intercontinental correlation of the nonmarine Cretaceous, for the division of the Jurassic and Cretaceous, and for proof of the integrity of the Laurasian continent.

Mesozoic continental facies are well developed and are continuously exposed in western Liaoning Province, where they contain abundant fossils. This is the type area of Grabau’s Jehol fauna. The Fuxin basin, with its typical Mesozoic continental facies, occupies a northeast-trending graben 80 km long, which formed in the Early to late Middle Jurassic and was superposed on the Indo-Sinian tectonic system. The graben ceased to be active in late Early Cretaceous time.