The Danish-Polish Trough—a northwest to southeast striking basin—is bordered by the Fennoscandian Shield in the north and the Ringköbing-Fyn High in the south. During the Late Cretaceous and Early Tertiary carbonate sedimentation prevailed. Locally small bryozoan mounds were formed during the Upper Maastrichtian. The bulk of bryozoan bioherms originated during the Danian B to C. Coral communities and coral mounds are confined to the Danian C. About five coral limestone localities occur within the Danish-Polish Trough; Fakse is the most important one.

Paleontological and sedimentological data of the coral limestones point to the interpretation of the coral reefs as “cold- and deep-water coral bioherms”.

Important criteria are the (1) absence of algae, (2) low-diverse azooxanthellate coral community, (3) dominance of dendroid growth forms in the corals, (4) surrounding pelagic facies adjacent to the coral mounds, (5) occurrence of pelagic organisms (globigerinid foraminifera, coccoliths) within the micrite of the mound facies and intermound facies, (6) breakdown of framebuilders predominantly by bioerosion instead of mechanical destruction, (7) mound- or bank-like structure of the buildups, (8) occurrence at a high paleolatitude.

Three major facies types can be distinguished: (1) bryozoan limestones, (2) transitional facies, and (3) coral limestones which include five subfacies types defined by the predominating coral taxa. Most coral mounds are composed of facies types 2 and 3.

Diagenesis is characterized by the formation of early marine-phreatic fibrous and bladed cements and by late diagenetic meteoric-phreatic dog-tooth cements and the replacement of calcite cements by quartz.

The mounds have an asymmetrical shape caused by unidirectional currents from the south. The maximum length is 200 m, the height 30 m and the width 80 m. The distribution of colonial corals within the mounds indicates a zonation pattern.

Framebuilders are represented only by azooxanthellate organisms: Colonial scleractinian corals, stylasterine hydrozoans and octocorals. Scleractinian corals have dendroid and arborescent growth forms, whereas hydrozoans and octocorals form fan-like colonies. Strong bioerosion of the framebuilding organisms was responsible for the breakdown of the skeletons; the bioclasts formed the substrate for other framebuilders. The soft bottom between the framebuilders was burrowed by bivalves and crustaceans.

The comparison with coral mounds occurring in the eastern Atlantic at similar latitudes and in a position comparable with that of the Paleocene Danish-Polish Trough suggests a paleodepth between 100 and 300 m.