Evolution of fluvial systems in salt-walled mini-basins: A review and new insights

The preserved sedimentary expression of fluvial successions accumulated in salt-walled mini-basins records the complex history of basin subsidence, the style of sediment supply, and the pattern of sediment distribution in response to a range of fluvial processes throughout the evolution of such basins. Temporal and spatial variations in the rate of basin subsidence govern the generation of accommodation space, whereas the rate and style of sediment supply govern how available accommodation is filled; together these parameters act as principal controls that dictate the gross-scale pattern of fluvial sedimentation. Additional factors that influence fluvial stratigraphic architecture in salt-walled mini-basins are: (i) the trend and form of inherited basement lineations and faults that control the geometry, orientation and spacing of salt walls that develop in response to halokinesis; (ii) salt thickness and composition that dictate both the maximum potential basin-fill thickness within a developing mini-basin and the rate of evacuation (migration) of salt from beneath evolving mini-basins, leading to the growth of confining salt walls, uplift of which may generate surface topographic expression that influences fluvial drainage patterns; (iii) climate that dictates fluvial style and the processes by which sediment is distributed; and (iv) the inherited direction of drainage relative to the trend of elongate salt walls and locus of sediment supply that dictates how sediments are distributed both within a single mini-basin and between adjacent basins. Examples of fluvial sedimentary architectures preserved in salt-walled mini-basins from a number of geographic regions are used to illustrate and document the primary controls that influence patterns of fluvial sediment accumulation. The distribution of fluvial architectural elements preserved within mini-basins follows a predictable pattern, both within individual basin depocentres and between adjoining basins: drainage pathways preferentially migrate to topographic lows within basins, such as developing rim-synclines, and away from topographic highs, such as uplifting salt walls or developing turtle-back structures. This paper demonstrates a range of fluvial–halokinetic interactions through consideration of a series of case studies, which demonstrate the current understanding of fluvial response to salt-walled mini-basin evolution and which highlight gaps in the current understanding.