The argillaceous dolomite concretions occur mainly in the intercalations of the greyish green silty mudstones,shales and ostracod beds in the Nenjiang Formatin of the Cretaceous Songliaocontinentalbasin.
松辽白垩纪陆相盆地嫩江组泥质铁白云岩结核主要呈顺层状产于灰绿色粉砂质泥岩、页岩与介形虫层的互层层序中。
