Palaeochannel

Factors external to a river system that might cause an avulsion include fault activity, sea-level rise, or an increase in flood peak discharge.

[6][7] As the importance of coarse-grained fluvial deposits associated with palaeochannels as sources of groundwater and favoured conveyance of subsurface water became appreciated, geophysical techniques sensing the physical properties of underlying ground and bedrock and groundwater and other fluids contained within them became more important and widely used.

[8][9] For example, palaeochannels can be identified using airborne electromagnetic surveys, as the coarse-grained sediments are more electrically resistive than surrounding materials.

The data derived from the analysis of their morphology and the fossils and palaeoenvironmental proxies can be used to study changes in regional palaeohydrology, palaeoclimates, and palaeoenvironments over geological and historic time scales.

[11] The morphology and distribution of palaeochannels can also be used to reconstruct the types, prehistory, and geometry of tectonic deformation, such as faulting, folding, uplift, and subsidence within an area.

[13][14][15] The sediments or sedimentary rocks filling palaeochannels also often contain dateable material, micro- and megafossils, and palaeoenvironmental proxies.

[18][19] Finally, the theoretical equilibrium profiles of rivers and streams provide a datum by which to detect and quantify tectonic processes such as faulting, uplift, and subsidence.

Although layers of lignite and other types of coal are sometimes part of the sedimentary fill of palaeochannels, they are typically too thin and narrow to be economically mined.

Also, bedding and jointing within strata comprising palaeochannels typically result in hazardous conditions related to unstable highwalls in opencast mines and collapsable roof rock in coal adits.

[29][30][31] Coarse-grained (sandy) palaeochannels and palaeovalleys have been proposed as reservoirs or conduits for the preferential underground flow of fresh water.

[33][34] The nomenclature of palaeochannels must reflect their actual physical character, origin, and evolution if their relationship to mineral and groundwater resources is to be properly understood.