Title: Depositional Environments and Sedimentary Facies
1Depositional Environments and Sedimentary Facies
2Depositional Environments
- Areas of the Earths surface where distinct
processes generate specific geological
(sedimentary) products
-Physical -Biological -Chemical
3Sedimentary (litho) Facies and (litho) Facies
Analysis
- Sedimentary (litho) facies
- Lithostratigraphic Units (time independent)
- Defined by sum total of (relevant) rock
properties - Reflects processes during genesis and may include
- Lithology
- Sedimentary Structures
- Fossils
- Bedding style and geometry (on various scales)
- Paleo-sediment transport indicators
- e.g. hummocky cross stratified, Zoophycus
burrowed, fine- to medium-grained, sandstone
4Facies Analysis, Facies Associations, Facies
Sequences, and Facies Models
- Otbo reoccurring associations of sedimentary
facies - (hummocky cross stratified, Zoophycus burrowed,
fine- to medium-grained, sandstone Storm Shelf,
Hummocky Sequence )
- It is possible to more precisely determine the
sum total of processes active at the site of
deposition and interpret depositional
environment - Facies sequences are recurring (in the geological
record) facies associations which occur in a
particular order due to the inherent temporal
changes in depositional conditions in particular
depositional environments
5Common Siliciclastic Stratigraphic Successions
- Vertical successions characterized by lithology,
associations and vertical arrangement of
sedimentary structures - Indicative of particular sedimentary depositional
environments - Expression of Walthers Law
- Reflects Autocyclicity
- stratigraphic variability inherent to a
particular depositional environment
6Distinctive and Common Sedimentary Facies
Associations
- High gradient, low sinuosity, sand and gravel
dominated - BRAIDED RIVER SYSTEM
7Distinctive and Common Sedimentary Facies
Associations
- Low Gradient, high sinuosity, mud to sand
dominated - MEANDERING RIVER SYSTEM
8Distinctive and Common Sedimentary Facies
Associations
- Sediment gravity flow-dominated (turbidity
currents), deep water sediment dispersal - SUBMARINE FAN SYSTEM
9Facies Analysis, Facies Associations, Facies
Sequences, and Facies Models
- Otbo reoccurring associations of sedimentary
facies - (hummocky cross stratified, Zoophycus burrowed,
fine- to medium-grained, sandstone Storm Shelf,
Hummocky Sequence )
- It is possible to more precisely determine the
sum total of processes active at the site of
deposition and interpret depositional
environment - Facies sequences are recurring (in the geological
record) facies associations which occur in a
particular order due to the inherent temporal
changes in depositional conditions in particular
depositional environments
10Common Sedimentary Facies Associations in
Carbonate Dominated Environments
11Common Sedimentary Facies Associations in
Carbonate Dominated Environments
- Carbonate sediment dominated, rimmed shallow
marine shelf - RIMMED CARBONATE SHELF SYSTEM
12Facies Analysis, Facies Associations, Facies
Sequences, and Facies Models
- Facies Models are a general summary of a given
depositional environment or depositional system - Lithostratigraphic unit representing depositional
processes and geographic location
- The apparent existence of order in Nature suggest
that there are (and have been through geological
time) a limited number of different and
recognizable depositional systems - These depositional systems are identified
through the use of - Facies Models
13Facies Analysis and Walthers Law
- It is a basic statement of far reaching
significance that only those facies and facies
areas can be super imposed primarily that can be
observed beside each other at the present time
14Facies Analysis and Walthers Law
- Gradational (vertical) transitions from one
facies to another indicate original adjacency and
genetic relationship during formation. - Sharp/erosional (vertical) contacts between
facies provides NO evidence of contemporaneous
genetic relationship of depositional environments
15Depositional Systems Analysis
- Depositional Systems (lithostratigraphic units)
- Three dimensional assemblages of lithofacies,
which are interpreted to be genetically linked
by process and environment
16Actualism and "Genetic Stratigraphy"
- Recognition of Uniformitarianism
- the relationship between modern processes of
sedimentation and the rock record
17Lithostratigraphy
- Formations, Members, Groups, etc.
- Material Units and "Classical Layer Cake
Stratigraphy - catastrophism continuous layering time
equivalence - NO!
- Further organization and subdivision of the rock
record otbo - Relative age
- Superposition, unconformities, cross cutting
relationships, included fragments - Original Horizontality
- Lateral Continuity
18Objective Subdivision of the Stratigraphic Record
Into Distinct Lithostratigraphic Units
- Formations
- with a type section, geographic or lithologic
name, and definition based on - limited and distinctive lithologic variability
- consistent stratigraphic context
- extensive map distribution in the surface or
subsurface
- Groups and Supergroups
- Are formations lumped otbo stratigraphic
association - Members and beds
- Subdivisions of Formations
- lithostrat units with less areal extent defined
as it is useful