The Sinuiju Formation(신의주층) is a geologic formation in North Korea. Formerly of uncertain age, it is now thought to be Early Cretaceous. A variety of fossils are known from the formation, including those of anurognathid pterosaurs and birds such as the specimen of a very large enantiornithine with a 5 cm (2.0 in) long tibia and a 3.5 cm (1.4 in) long pygostyle. Frogs have also been found in the formation. Numerous compression fossils of insects have also been found.