Delta environments and paleogeography

Maya Elrick

University of New Mexico

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This page first made public: Jul 10, 2006

Summary

One of the most basic and useful aspects of stratigraphy is reconstructing paleogeography using correlated stratigraphic columns. This lab introduces students to the reconstruction of deltaic paleoenvironments through three time slices using stratigraphic columns, facies analysis, bentonite marker beds, and paleoflow indicators (using rose diagrams). Construction of the paleogeographic maps teaches students to think in 3-dimensions and through time, and forces them to make educated interpretations based on limited data control.

Stratigraphy, Depositional environments, Facies and Facies Models | College Upper (15-16)

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Context

Audience

Presently designed for junior/senior undergraduate geology (or environmental science) majors, but could be modified for more advanced (graduate level) or less advanced levels (Earth History).

Skills and concepts that students must have mastered

Prerequisite knowledge of interpreting basic stratigraphic columns (symbols, scales, etc), basic delta and fluvial processes, facies, and dynamics (provided in lecture portion of class), and basic formation of basic sedimentary structures.

How the activity is situated in the course

Stand-alone lab taught after lecture has covered fluvial and deltaic environments and sedimentary structures. Students are given 3 hours of supervised lab time and the rest of the week (on their own time) to complete the lab.

Goals

Content/concepts goals for this activity

Learning to interpret depositional environments from facies information, constructing and interpreting Rose diagrams, and drawing paleogeographic maps using Walther's Law and basic stratigraphic principles.

Higher order thinking skills goals for this activity

Transferring 2D stratigraphic information (stratigraphic columns to 3D paleogeographic maps, linking and visualizing movement of environments through time, constructing and scaling maps, identifying and distilling graphical data for interpretations, and interpolating between limited data points using sound geologic knowledge.

Other skills goals for this activity

Description of the activity/assignment

Students are given 4 hypothetical stratigraphic columns (each roughly 30 m thick) of deltaic deposits, 3 base maps with section locations, and a map scale. Students subdivide the stratigraphic units into subfacies and interpret subenvironments (delta plain, delta front, prodelta, marine) and describe/list features used to make these interpretations. Using depositional interpretations, 3 bentonite marker beds, and paleocurrent information, students draw 3 successive paleogeographic maps of the region showing delta migration through time.

Determining whether students have met the goals

Students turn in and are graded on their 3 maps, interpreted stratigraphic columns (including the list of features they used to interpret each subenvironment), 5 Rose diagrams, and short write up describing observed trends through time. Most of grade is based on their maps checking for geologically sound and logical interpretations, flow directions, migration directions, realistic scale, and reasonable interpolation between data points.

More information about assessment tools and techniques.