A collection of posts on depositional processes, bedforms, and stratigraphic architecture for major depositional systems. Comparisons with planetary systems include those on Mars, Venus, and Titan.
The article Depositional systems and systems tracts summarizes these principles in a Sequence Stratigraphic context. The following paragraph is excerpted from that post.
“Stand back and observe an active, modern delta, any delta – any closer and you’ll get bogged down in detail; aerial and satellite images are best (part of the Mackenzie delta is shown above). You will see an array of depositional environments: distributary channels, delta plains, crevasse splays, the front of the delta lapped by waves, and sediment plumes that will feed deposition on the prodelta slope. Some inactive segments of the delta may have been reworked into sand bars and spits that front a lagoon or embayment. All these environments are spatially distinct and yet they are dependent, one on the other. We can think of the entire delta as an integrated depositional system, where individual depositional environments are linked by all those physical, biological, and chemical processes that contribute to sediment supply and deposition, and the construction of a stratigraphic succession.
A modern depositional system can be described as a 3-dimensional array of genetically related environments. The expression “genetically related” is important. For the delta example, the distributary channels do not occur in isolation – sediment transport within the channels depends on fluvial and alluvial processes upstream, and a sink at the delta front terminus (i.e. the destination for sediment). Even though the processes may change from one environment to the other, they are inextricably linked.
We can also think of a depositional system in terms of its sedimentary facies and facies associations, for example a delta will include (among many other facies), crossbedded channel sands, peats and soils on the vegetated delta plain, interbedded sandstone-mudstone across the floodplain and crevasse splays, and mud-dominated facies in the prodelta. Applying the facies concept to depositional systems is crucial for interpreting ancient delta systems and unraveling the 4th dimension – time.
Thus, the definition of a depositional system, in the context of the rock record, can be expanded to include the 4-dimensional assemblage of genetically related facies. However, keep in mind that while we can observe directly the various processes and responses in modern systems, for ancient depositional systems we must infer the process-response of each sedimentary facies based on the kind of inductive reasoning permitted by uniformitarianism. This principle applies to other planetary environments as much as it does to Earth.
