Fluvial-aeolian interactions result from both short-term interplay between an ergmargin and adjacent fluvial system, and much longer-term expansion and contraction of the erg in response to climatic, tectonic or eustatic effects.Near Moenkopi, in northeastern Arizona, a zone of intertonguing characterizes the transition between the fluvial Kayenta Formation and the overlying aeolian Navajo Sandstone. Three fluvial to aeolian drying-up cycles form the largest scale interaction and represent the repeated advance of the Navajo erg across the Kayenta alluvial plain, probably in response to an increasingly arid climate. During the aeolian phase of each cycle, small-scale interactions resulted from fore-erg deposition on the alluvial plain, and fluviallyfed interdunal flooding, which both occurred during periods of erg activity.The top of each cycle marked a return to wetter climatic conditions which terminated erg activity, forming a stabilization surface. As a consequence, prograding fluvial systems were able to transgress the denuded surface, covering the area formerly occupied by the erg to form the base of the next drying-up cycle.From a hydrocarbon reservoir viewpoint, the two types of interaction have contrasting geometries. Fluvial deposits of the large-scale cycles have regionally extensive sheet-like geometries and are likely to form widespread barriers to vertical flow. Small-scale interdunal flooding is less significant and forms ribbon-like baffles to flow which extend roughly parallel to the strike of the aeolian cross-strata. The key to differentiating each type of interaction lies in determining whether the fluvial syste coexisted with the active erg, or prograded as a result of erg stabilization.

Two distinct units can be recognized in the Lower Triassic Ormskirk Sandstone Formation in the East Irish Sea Basin. Perennial fluvial channel, lacustrine and minor aeolian sandstones dominate the upper part, but the lower is characterized by thick (tens of metres) enigmatic wavy bedded deposits interbedded with aeolian and minor fluvial channel sandstones. Previous interpretations that invoked an overbank ‘sheetflood’ or ‘sandflat’ origin for the wavy bedding are difficult to reconcile with the sedimentary structures, which are more consistent with algal and evaporitic processes in modern sabkhas. These deposits contain widespread (km) ‘drying upward’ patterns 2–10 m thick, reflecting a sabkha to more aeolian dominated setting. Such thicknesses are consistent with an origin related to 23 000 year Milankovitch cyclicity. The lower, wavy bedded portion of the Ormskirk Sandstone Formation is regionally truncated by fluvial channel-belt sandstones. Their extent reflects a combination of high sediment supply, uniform subsidence and low basinal relief. Lacustrine units near the top of the formation can be correlated regionally, with one passing southward into a major aeolian unit that thickens to 60 m in the south of the basin. This transition demonstrates the diachroneity of the Mercia Mudstone Group transgression. The key to correlating the Ormskirk Sandstone Formation lies in identifying intervals dominated by fluvial, lacustrine or sabkha-aeolian deposits. Correlation of water-table-controlled ‘drying upward’ patterns within sabkha-aeolian deposits allows finer scale subdivision, and provides an estimate for the degree of fluvial truncation at the top of the unit.

Hydrocarbon migration from the Faeroe-Shetland Basin source kitchen into the Mesozoic back basins that flank its southern margin is prevented by basement highs such as the Rona Ridge. The back basins have long been considered non-prospective due to a perceived lack of source rock and insufficient burial to generate commercial hydrocarbons. The Triassic Strathmore discovery made in 1990, followed by the Upper Jurassic Solan discovery the following year, have demonstrated the prospectivity of the East Solan Basin and similar back basins along the same trend. The two discoveries typify the potential plays in this area, which consist of tilted Palaeozoic and pre-Upper Jurassic structural traps, and syn-to post-Upper Jurassic pinch-out plays against the surrounding structural highs.Strathmore, which straddles UK Blocks 204/30a and 205/26a