During Rhaetian-Sinemurian time a large wave- and storm-dominated hydrologically closed lake was situated in the Jameson Land basin, East Greenland. The lacustrine succession consists of alternating black unfossiliferous organic-rich mudstones and sheet sandstones. Anoxic conditions dominated at the lake bottom during deposition of the muds, and the water column was probably stratified. Water depth during deposition of the muds exceeded several tens of metres and probably reached a hundred metres. The sandstones were deposited by progradation of wave-dominated deltas in a water depth of less than 15 m. High-resolution sequence stratigraphic interpretation suggests that the mudstones were deposited in periods of rising and high stand of lake level, whereas progradation of the deltaic sheet sandstones took place during forced regressions caused by significant fall. The lake thus underwent a large number of fairly high-amplitude changes in level, probably caused by climatic fluctuations. The high-frequency cycles can be grouped into several low-frequency cycles that show the same number of major fluctuations as published eustatic sea-level curves. This similarity suggests a causal link between eustasy and long-period variations in lake level. Recognition of lowstand shorelines in association with the process of forced regression has led to recognition of a new stratigraphic play type in the Jameson Land basin. Lowstand deltaic sandstone bodies, isolated in organic-rich lacustrine shales with a suitable maturity for hydrocarbon generation, occur in an extensive area in southern and central Jameson Land. In these parts of the basin this play type may be attractive for exploration assuming optimal conditions for hydrocarbon preservation. The Kap Stewart black shale-forced regressive sandstone play type may be applied to similar lacustrine successions elsewhere.