Introduction to Carbonate Facies, Depositional Environments, and Depositional Systems: Facies Tracts

Introduction to Carbonate Environments, Facies, and Facies Tracts

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

Design Objectives

FACIES-TRACT PATTERNS

Facies tracts are distributed across a platform or ramp in response to physical, biological, and chemical processes. Distinct facies-tract patterns form according to the distribution and intensity of the processes. An example of a facies-tract pattern across a modern leeward platform is presented below. Please note that “facies” is a concept for rocks, but in this section we apply it to modern environments in order to teach the concept.

At top: Photograph from space showing the area from Cat Cay platform margin on the left to Andros Island on the right. Facies tracts are labeled. Place cursor over photo to see a facies-tract map showing the facies tracts on the platform. Alignment of the facies tracts across the platform produces a predictable pattern that is based on the processes affecting the platform. Projected below: a simplified topographic cross section of the platform showing the facies tracts.