Introduction to Carbonate Facies, Depositional Environments, and Depositional Systems: Definition of Depositional Enviromnment

Introduction to Carbonate Environments, Facies, and Facies Tracts

Robert G. Loucks, Charles Kerans, and Xavier Janson
Bureau of Economic Geology

Design Objectives

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, and

(3) tidal-channel facies.

Cat Cay platform-margin sand-shoal complex along the west margin of the Great Bahama 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) reef-front facies,

(2) reef-crest facies,

(3) reef-apron facies, and

(4) tidal-channel facies.

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