Subsurface sediment remobilization and fluid flow in sedimentary basins: an overview

TLDR: In this paper, the authors provide spatio-temporal information to constrain the mechanics of deep subsurface sediment remobilization as these processes can not be readily observed, unlike many conventional sediment transport phenomena.

Abstract: Subsurface sediment remobilization and fluid flow processes and their products are increasingly being recognized as significant dynamic components of sedimentary basins. The geological structures formed by these processes have traditionally been grouped into mudvolcano systems, fluid flow pipes and sandstone intrusion complexes. But the boundaries between these groups are not always distinct because there can be similarities in their geometries and the causal geological processes. For instance, the process model for both mud and sand remobilization and injection involves a source of fluid that can be separate from the source of sediment, and diapirism is now largely discarded as a deformation mechanism for both lithologies. Both mud and sand form dykes and sills in the subsurface and extrusive edifices when intersecting the sediment surface, although the relative proportions of intrusive and extrusive components are very different, with mud volcano systems being largely extrusive and sand injectite systems being mainly intrusive. Focused fluid flow pipes may transfer fluids over hundreds of metres of vertical section for millions of years and may develop into mud volcano feeder systems under conditions of sufficiently voluminous and rapid fluid ascent associated with deeper focus points and overpressured aquifers. Both mud and sand remobilization is facilitated by overpressure and generally will be activated by an external trigger such as an earthquake, although some mud volcano systems may be driven by the recharge dynamics of their fluid source. Future research should aim to provide spatio-temporal \\\\\\\'injectite\\\\\\\' stratigraphies to help constrain sediment remobilization processes in their basinal context and identify and study outcrop analogues of mud volcano feeders and pipes, which are virtually unknown at present. Further data-driven research would be significantly boosted by numerical and analogue process modelling to constrain the mechanics of deep subsurface sediment remobilization as these processes can not be readily observed, unlike many conventional sediment transport phenomena.