Facies and facies associations Flashcards
Define a facies
A body of sediment or rock characterised by a particular combination of lithological, phyiscal, and biological characteristics that distinguish it from the units above, below, and adjacent to it
Give three examples of facies descriptors
Sedimentary/biological structures, texture, grain type/composition
What is the scale of facies based on?
Scale is arbitrary and driven by pragmatism (time, effort, money, purpose)
Why is it logical to assign processes to individual facies?
Facies are often non-unique rather than characteristic of a singular depositional environment
What is the limitation of assigning proccesses to similar facies?
Similar facies may be created by different processes
What do lithological characteristics allow?
Observation, measurement, and description
What do facies allow?
Interpretation of processes of transport and deposition
What do facies associations/sequences allow?
Interpretation of deposition environments and the combination of processes
Describe the ‘architecture’ of stratigraphic successions
3d patterns produced by facies associations
What does the architecture of stratigraphic successions allow?
Interpretation of climatic and tectonic changes through time, implying the geographic distribution of environments in sediementary basins
Define facies association
A collection of multiple, genetically-related facies formed within a single depostional system
Give four analogues that can be used to make an environmental interpretation from a facies
Modern, ancient, theoretical, experimental
When are facies associations given names? Give an example
When they are found repetitively found in the stratigraphic record
e.g. Bouma sequence, often associated with turbidites
Define a point bar
The deposition of sediment on the inside bend of flowing water
Water flows slower here
Describe a cut bank
The depostion of sediment on the outer bank of flowing water
The water flows faster and deeper
Grains deposited here are coarser
