Depositional Settings

The depositional settings of the sedimentary section are interpreted from outcrop, and/or associated wells, and/or seismic, by comparing their character to modern depositional systems. This form of geological interpretation has probably been around since humans have exploited the earth. However, following the publication of James Hutton's monumental tome the "Theory of the Earth" in 1788, this approach became formally recognized. Geologists, particularly sedimentary stratigraphers, then officially recognized that "the Present is the Key to the Past". Using this concept they were able to continue to predict the character and areal extent of sedimentary rocks from known areas to those where less data is available. Now geologists interpret and compare the rocks they examine with analogous modern depositional settings using a combination of:
  • Sedimentary petrology [mineralogic composition and fabric of the component sedimentary grains and their cements]
  • Sedimentary structures and sediment geometry 
  • Fossil assemblages
  • Sequence stratigraphic signal
  • Plate tectonic setting
The prediction of the sediment character, geometry and extent away from known areas is better when all of the above are used but often some may not be available. For instance this web site records how sedimentary stratigraphers use sequence stratigraphy as a tool to both interpret the depositional setting of the sedimentary section and also predict the lateral continuity of the component facies.

This site provides an overview of both modern and ancient depositional systems and their character in terms of items listed above. These systems include:

Clastic Systems
 
Marine
• Barrier island coasts
• Deltaic systems
Deepwater fans
• Deepwater basins
Continental
• Glacial
• Aeolian
• Alluvial Fans
• Braided Streams
• Coarse and fine grained fluvial systems
• Lacustrian

Carbonate Systems - Marine
• Inner carbonate shelf
• Outer carbonate shelf and Margins
• Deepwater carbonates

Each of the modern and ancient depositional systems is explained, and illustrated in terms of their general plate and geomorphic setting, along with the geometry and sedimentary facies that are common components of the systems, the common sedimentary structures, common flora and fauna, and the critical differences between lowstand, transgressive and highstand systems tracts, and their relationship to the major subdividing parasequence surfaces.
The characteristics of the different depositional systems are illustrated with figures created by  various author, downloaded from the web, and from the literature. As with a scientific paper, where ever possible, all the sources of this publications are cited. Many of the currently linked items accessed through the pull down menu above were created in class projects by both undergraduate and graduate students.

Friday, March 29, 2013
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