Sedimentological and ecological analysis of sequences in the marginal Wealden facies of northwest Germany has revealed a transition from fluvial (meandering and anastomosing) to deltaic and lagoonal environments, each of which is associated with coal formation. The various environments of coal formation involving different types of sedimentary controls are described in terms of five models.

Thin, impure, and laterally discontinuous coal seams largely consisting of conifer needles (Abietites) can be recognized as an allochthonous accumulation along the shores of flood-plain lakes in an anastomosing fluvial system (Hils model). More continuous vitrainous seams in the Osterwald area exhibit a symmetric petrographic seam profile and are considered to be formed in flood-plain swamps in response to the migration of a meandering fluvial channel (Osterwald model). Basinward and farther north coal seams are associated with littoral and lagoonal environments and considered to be derived from peat swamps formed on washover fans or in protected lagoonal bays (Bückeburg and Deister models). South of Osnabrück coal accumulation can be related to the upper part of a deltaic sequence (Osnabrück model).