Geol 370: Sedimentology and Stratigraphy Topic 18: Paleogeography and Systems Tracts

1. Scales of Study
Sedimentology is performed on a number of scales from single grains
to tectonic and hydrologically-driven global sea-level cycles.
Clast
Deposit/rock
Environment/facies
System/facies association/
architectural element
Systems tract
Increasing scale and complexity
Basin
Eustatic
Sedimentology
Stratigraphy

2. Clast
Deposit/rock
Environment/facies
System/facies association/
architectural element
Systems tract
Increasing scale and complexity
Basin
Eustatic
Sedimentology
Stratigraphy
Scales of Study

3. Systems Tract
A systems tract consists of genetically-related (time-equivalent)
depositional systems.

4. Types of Systems Tracts
Systems tracts are divided into four categories: falling-stage, lowstand,
transgressive, and highstand, depending upon their relationship to
relative base-level change.
LowstandHighstand

5. Ancient Systems Tracts
Systems tracts can be recognized in the ancient record by their facies
associations.

6. Paleogeographic Reconstruction
Systems tracts are a new way to look at the older concept of
paleogeographic reconstruction, which involves regional facies analysis.

8. Regional Correlation
Paleogeographic reconstruction is based on correlation of data from
numerous localities in the form of measured sections, logged wells, or
both.

9. Hanging a Section
The stratigraphic succession of a basin can be “hung” on different
horizons to distinguish the impact of different depositional events.

10. Sequence Stratigraphy
A stratigraphic sequence consists of sediment deposited during a
single cycle of sea-level fluctuation and is identified, in part, by the
presence of systems tracts representing different phases of that cycle.
Clastic Sequence Carbonate Sequence