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Facies and Facies Models

What is a facies?

A sedimentary unit with consistent characteristics (lithology, grain size, texture, structures, etc.) that formed under specific depositional conditions.

What are facies models?

An idealized vertical succession of facies that would be expected from the migration of depositional environments within a particular setting (e.g., sandy braided river model, wave-dominated delta model).

Walther’s LawRationale for interpreting vertical facies succession is based on Walther’s LawVertical succession of facies represents migration of laterally adjacent depositional environments, unless there is evidence of erosion (unconformity)

Constructing a facies model:1. Identify important

surfaces (especially erosional)

Constructing a facies model:2. Interpret facies using

knowledge of sedimentary processes and modern environments

Constructing a facies model:3. Determine characteristic

vertical succession of facies