1. Depositional Environments and Sedimentary Facies

2. Depositional Environments
Clastic vs. Carbonate Depositional Systems
Short and Long Depositional Systems

3. Facies
The sum of the characteristics of a sedimentary unit resulting from some particular set of physical, chemical and biological parameters that work to produce a unit with specific textural, structural, and compositional properties (after Boggs, 2001)
Generally interpretive
Not specific to a rock, but to a predicted set of characteristics associated with some depositional environment
Sometimes used differently
E.g., To describe a rock unit in an outcrop
sandstone facies

4. FACIES
“The nature of the material deposited anywhere will be determined by the physical, chemical or biological processes which have occurred during the formation, transport and deposition of sediment. Those processes also define the environment of deposition”
Nichols, 2001.

5. FACIES Lithofacies Biofacies Ichnofacies Based on lithology
Based on fossil assemblage
Ichnofacies
Based on trace fossil assemblage

6. Facies Types Lithofacies Biofacies
characteristics of a rock which are the products of PHYSICAL and CHEMICAL processes
coarsening upward, fining upward
Biofacies
observations are based on fauna and flora present
Ichnofacies focuses on trace fossils
Examples
gray limestone rock = lithofacies
echinoid and crinoids = biofacies
burrows and tracks = ichnofacies

7. Environment of Deposition
Sedimentological analyses allow us to determine the environment in which a sequence of sediments or rocks accumulated
Texture
Composition/ Classification
Petrographic analyses (e.g., evaluate diagenesis)
Identify sedimentary structures
Compare results to modern environments
Also simulate conditions in laboratory experiments (Hjülstom’s curve)

8. Depositional Environments and Sedimentary Facies

9. Depositional Environments
Areas of the Earth’s surface where distinct processes generate specific geological (sedimentary) products
Physical
Biological
Chemical

10. Sedimentary (litho) Facies and (litho) Facies Analysis
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

11. Paleocurrents and Paleocurrent Indicator Analysis
Paleocurrent indicators are oriented sedimentary structures interpreted to have been deposited by ancient flows
Cross-beds slip faces,
pebble imbrication,
parting lineation,
tool marks and groove casts, and
ripple crest orientation

12. Unidirectional Paleocurrent Indicators

13. Cobble Imbrication

14. Bidirectional Paleocurrent Indicators

15. Rose Diagram

16. Facies Analysis, Facies Associations, Facies Sequences, and Facies Models
Reoccurring associations of sedimentary facies
(x-bdd channel fill sst with root mottled, mud cracked silt and clay stone see point-bar model)
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

18. Distinctive and Common Sedimentary Facies Associations
Vertical successions principally identified by lithology, associations and vertical arrangement of sedimentary structures
indicative of particular sedimentary depositional environments

19. DELTA

20. Distinctive and Common Sedimentary Facies Associations
Vertical successions principally identified by lithology, associations and vertical arrangement of sedimentary structures
indicative of particular sedimentary depositional environments

22. Distinctive and Common Sedimentary Facies Associations
Vertical successions principally identified by lithology, associations and vertical arrangement of sedimentary structures
indicative of particular sedimentary depositional environments

23. Distinctive and Common Sedimentary Facies Associations
Vertical successions principally identified by lithology, associations and vertical arrangement of sedimentary structures
indicative of particular sedimentary depositional environments

24. Facies 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

25. Facies Analysis and Walther’s 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”

26. Facies Analysis and Walther’s 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

28. Depositional Systems Analysis
Depositional Systems: (lithostratigraphic units)
Three dimensional assemblages of lithofacies, which are interpreted to be genetically linked by process and environment

29. Environments of Deposition
Continental
Fluvial alluvial fan, braided stream, meandering stream
Desert dunes, playa lakes, salinas
Lacustrine
Glacial
Deltaic delta plain, delta front, prodelta
Marginal- Marine
Beach/ barrier island
Estuary/ lagoon
Tidal Flat
Neritic continental shelf, organic reef
Marine
Pelagic continental slope and rise, deep- ocean floor

30. Environment of Deposition
Modern Analogue
Key to interpretting transport history of sediments and rocks
Process/ Response Model
Based on idea that a “particular set of environmental conditions operating at a particular intensity will produce a sedimentary deposit with a unique set of properties that will identify if as the product of a particular environment” Boggs, 2001
Unique solution is overly optimistic!
Very useful nonetheless!

31. Process/ Response Model
Examples
Process Element
Ocean Basin
Deep water; low current velocity; settling dominates
Response Element
Laminated mudstone with abundant microfossils
As geologists, often have to work backwords
Obtain process from response
leads to set of predictions
what types of sedimentary structures/ associations will be deposited in different environments
sedimentary structures/ associations aregenerally not unique to a single environment
Loose definition for facies

32. Facies Analysis
The interpretation of strata in terms of depositional environments
How?
Recognize sedimentary environments
Interpret rocks based on facies
Because there are no unique solutions can’t simply analyze one outcrop and understand it!
Rely heavily on facies associations
Vertical
Horizontal
Can use idealized model to assist in analysis

33. Facies Models How facies models are created
NICHOLS FLOW CHART (FIG 5.1)
assign all beds in a succession to facies
look at patterns of distribution of facies
develop facies association and interpret in terms of depositional environment
e.g., fining upwards is associated with turbidite
there are OTHER environments that have fining up!
need multiple criteria!
some of the criteria
look at associations of facies within basin

34. Facies Models CAVEATS! function as GUIDES for INTERPRETATION!
can’t be SO inclusive to include everything
also may find that not everything is included
e.g., Bouma sequence!

35. How to perform a Facies Analysis
Procedure
1. Measure the section
2. Develop detailed graphic sedimentary log
use standard symbols
3. Evaluate associated section
Quantitatively or qualitatively
4. Compare to facies models
5. Assess regional associations

36. How to make a stratigraphic column
Look at the rocks This may seem obvious, but it is important before you begin to get a general sense of the rocks in front of you. It will make it easier to make a description of the rocks later if you get a good overview first.
Look for changes in rock type If the rocks in one part of the outcrop appear very different, then it is possible that they should be their own "unit". Dividing the rock outcrop into units is based on changes either in fossils, color, rock type, and other factors, or all of these factors combined.
Measure the section Once you have determined different units, you may then measure the thicknesses of these units. (Geologists are generally not particularly interested in the length of the rocks, only the widths.)
Start describing! Now it's time to make specific observations about the rock you are looking at. What fossils do you see? What is the color? What kind of rock is it (sandstone, shale, limestone, or something else)?

38. STRATIGRAPHIC LOG

39. STRATIGRAPHIC LOG