Introduction to Carbonate Environments, Facies, and Facies Tracts
Robert G. Loucks, Charles Kerans, and Xavier Janson
Bureau of Economic Geology
 
 
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CONCEPT OF FACIES TRACT

A facies tract is a genetically linked association of lithofacies and vertical lithofacies successions that records a discrete energy/water depth/sediment supply setting (Kerans and Fitchen, 1995). Kerans and Fitchen (1995) stated that “because the facies tract represents a distinct energy regime/water depth/sediment supply, it must be defined through interpretation of depositional processes rather than lithologic parameters such as grain types. Therefore, a facies tract can be characterized by a variety of lithofacies.

 
Examples of facies tracts:
 

EXAMPLE 1. A platform-margin sand-shoal facies tract is composed of several main facies:

(1) shoal crest facies

(2) washover-fan facies

(3) tidal channel facies

 
Cat Cay platform-margin sand-shoal complex along the western margin of the Great Bahamas Bank. Dashed lines group an assemblage of facies into a facies tract.
 

EXAMPLE 2. A platform-margin reef facies tract is composed of several main facies:

(1) fore-reef facies

(2) reef-crest facies

(3) reef-apron facies

 
A well-developed platform-margin barrier reef offshore from southern Belize. Dashed lines group an assemblage of facies into a facies tract.

 
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