Anomalous mound-forming limestones, here termed the Kuhnpasset Beds, occur within Late Barremian (Early Cretaceous) mudstones on Wollaston Forland, Northeast Greenland. The normal mudstones contain a sparse fauna of small nuculoids, arcoids and inoceramids; by contrast, the mounds contain an unusual faunal assembage, dominated by large bivalves. These include an abundant lucinid, Cryptolucina kuhnpassetensis sp. nov., and, less commonly, Solemya, both known seep-associated genera. Locally, a large modiomorphid, Caspiconcha whithami gen. et sp. nov., is common and reaches > 300 mm in length and has a shell up to 28 mm thick. Also, the wood-boring bivalve Turnus is abundant in driftwood. Gastropods are rare, but the associated cephalopod fauna includes ammonites, belemnites, nautiloids and a remarkable large orthoconic phragmocone. The form of the mounds with calcite-cemented tube systems, associated laminated calcite crusts and void fills, together with the fauna, is analogous to those of methane-based cold-seep complexes. However, preliminary studies indicate that much of the original aragonitic shell is now replaced by silica. This precluded conclusive geochemical studies based on the shells themselves. It is believed that the mounds formed on the seafloor in a mid- to outer shelf situation at the end of a period of extensional rifting on the eastern Greenland passive Atlantic margin. The vents occur near the footwall crest of a tilted fault block. The underlying faults may have provided routes or influenced direction of movement for nutrient migration. Source rocks were probably the Late Jurassic black shales from depths of < 600–1200 m. If methane was being generated, it was probably forming by shallow-depth organic breakdown rather than by thermogenic processes, which require greater burial.

A tectono-sedimentary model is proposed for the Cretaceous (post-Valanginian) succession of NE Greenland which provides insights into the evolution of adjacent margins. Subsequent to a major reorganization of fault blocks during rifting in the Volgian–Valanginian a seafloor topography controlled by block faulting was created and was maintained by faulting until the end of rifting in the Middle Albian. This topography was infilled after the Middle Albian and a shelf break margin was created and maintained until at least the Campanian. After this time there is no onshore sedimentary record in NE Greenland to constrain interpretations. Post-Valanginian sedimentation was dominated by the accumulation of fine sediments. However, significant thicknesses of coarse clastics are recorded at several stratigraphic levels in East Greenland. The primary controls on sandstone occurrence are steps in the basin bounding fault. The greatest accumulation of sandstones is associated with the largest of these steps. Sandstone supply to basinal areas was controlled by periods of lowstand. These have been identified in the Barremian, Late Aptian and Coniacian. Sandstone deposition occurred in fiuvio–deltaic, tidally influenced shallow marine and deep marine environments. The degradation of sandy footwall slopes did not lead to the formation of sandy sequences in the adjacent hanging wall successions.

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