In the early Nenjiang stage, a largest lake transgression occurred in the Songliao basin, depositing a group of black shale with intercalation of oil shale in the major areas of basin.
松辽盆地在嫩江早期发生了最大湖侵事件，在整个盆地范围内形成了一套黑色泥页岩夹油页岩。
2
The Donghe Sandstone was broadly deposited in the early stage of the marine transgression, but it is not an isochronous stratigraphic unit.