Building a Facies Model

William W. Little, Brigham Young University-Idaho
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Initial Publication Date: June 3, 2014 | Reviewed: June 24, 2014


Facies models are often abstract and difficult for undergraduate students to fully understand. As a result, they tend to memorize idealized diagrams from text books that can be reproduced for an exam, then forgotten.

The purpose of this exercise is to help students understand a model by "building" it "piece by piece" and relating the various components to concepts they learned earlier in the semester, such as energy relationships, base level, facies, facies associations, and Walther's Law. It is designed to begin as an in-class discussion led by the instructor using a black or white board, followed by group collaboration, out-of-class exercises, and concluding with a formal examination.

The example provided here is for a prograding shoreface system; however, the same approach can be applied to any depositional system.

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This exercise is designed for a required, semester-long undergraduate course in sedimentology and stratigraphy.

Skills and concepts that students must have mastered

The exercise should be conducted after students are familiar with rock classification, identification of sedimentary structures, and basic concepts of sedimentology, such as base level, accommodation space, and Walther's Law.

How the activity is situated in the course

For me, the approach demonstrated by this exercise is repeated for each major depositional system during the facies models portion (middle third) of my course in sedimentology and stratigraphy.


Content/concepts goals for this activity

Construction of facies models

Higher order thinking skills goals for this activity

The primary skill to be developed is an understanding of relationship between physical features (sedimentary texture and structures) and the processes (medium, energy) that formed them and to be able to apply this understanding to concepts of facies and facies associations and how they correspond to depositional environments and systems. The ultimate goal is, before reviewing published facies models, students be able to design reasonable models of their own.

Other skills goals for this activity

Students form groups of three to four to compare their work and make modifications to their individual models.

Students compare their models to published versions and to try to understand and explain differences. Part of this is to emphasize that there is a range of correct interpretations and to not become locked into thinking there is a single solution.

The assignment requires a written report at the end of each facies model, demonstrating how they would explain the model to another geologist.

Description and Teaching Materials

Step 1: Each facies model is introduced through an in-class discussion, during which the instructor guides students toward an understanding of basic concepts, such as energy regimes and the nature of boundaries (surfaces) between these regimes, as well as likely sediment characteristics, structures, and transport processes and directions. These items are outlined on a black- or white board as they are discussed. Though the shoreface system is used as an example in this document, a similar approach can be applied to any depositional system.

Step 2: Students work in groups of three or four to draft a reasonable facies model consisting of a plan view and both depositional strike and dip cross-sectional views. Though they compare and contrast their models in groups, each student is, ultimately, responsible for his/her own final model.

Step 3: Students compare and contrast their models to those from published sources to try to understand differences between interpretations. Part of this is to emphasize that there is a range of correct interpretations and to not become locked into thinking there is a single "correct" solution.

Step 4: Students prepare a final draft of their model, along with a written outline of how they would present/explain the model to others. This is submitted for a grade.

Step 5: Three models (two clastic and one carbonate) are chosen from the nine discussed in class for inclusion on an exam. Students reproduce their models and, in narrative form, flesh out their outlines. To avoid rushing them on the exam, I make it available over a three day time frame and allow them to come to my office when ready.

Teaching Notes and Tips

Instructor's Notes (Acrobat (PDF) 1.4MB May30 14)


The primary assessment criteria are that the models be relatively complete and "reasonable." I am not looking for a specific solution, but to receive full credit, I must be able to see that the models show the student's level of understanding and are not simply memorized and redrawn from a published source. Two grades are assigned, one for their out of class work and another from a formal exam.

References and Resources

There are many references for facies models. Some of those I make available include:

Facies Models by Walker & James

Depositional Sedimentary Environments by Reineck & Singh

Sandstone Depositional Environmnents - AAPG Mem. 31

Carbonate Depositional Environments - AAPG Mem 33