Sediment Dispersal and Continental Margin Stratigraphy

Kathleen Surpless, Adam Hoffman, Steven Kuehl, Lonnie Leithold

Summary

This is one component of the Source to Sink Mini Lesson Set

This module explores sediment dispersal and its impacts on margin geometry; students will use data (including data from the Fly and Waipaoa river systems) to explore how margin stratigraphy/geometry development occurs in the context of varying sediment dispersal systems.

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Learning Goals

Students will be able to:
  • describe the important aspects of sediment dispersal systems.
  • characterize sediment accumulation and dispersal systems utilizing visualizations and datasets available from MARGINS research.
  • evaluate how various factors impact the development of margin stratigraphy and geometry at specific sites.
  • predict how perturbations might alter sediment dispersal and the stratigraphic record.

Context for Use

This module can be incorporated into mid-level and upper-level undergraduate courses dealing with sedimentology and stratigraphy, sedimentary geology, basin analysis, geochemistry, paleoclimate, or oceanography. Students should have basic knowledge of sediment transport processes, sediment diagenesis and familiarity with graphing and analyzing scatter plots. In addition access to computers onto which visualization programs, such as the free and widely available GeoMapApp, have been installed. This 60 minute mini-lesson is readily adaptable and by mixing and matching data sets and visualization tools can be used as an in-class activity, lab, or homework assignment.

Description and Teaching Materials

This mini-lesson is divided into three parts - a hook to engage the students in the topic, a forray into sediment disperson systems, and examining shelf sedimentation characteristisc . Students will explore the differences between sediment dispersion systems. After understanding the differences they will utilize data to predict the type of dispersal systems for riverine systems around the world. Then they will focus on two MARGINS sites, Waipaoa River and the Fly River, and using GeoMapApp bathymetry and additional data for each system, students will compare and evaluate similarities and differences within a plate tectonics context. Using the bathymetry and seismic data, the students will be able to determine where sediment is being deposited within each of these systems, and then the students will evaluate stratigraphic characteristics for each system and contrast with present sedimentation patterns to determine if the stratigraphic record is consistent with the dispersal system noted in each environment. As a summative assessment piece, students will be asked to predict future stratigraphic development and dispersal patterns given current and predicted anthropogenic influences such as variations in land use practices and sea level.

PART I. Hook:

The goal of this brainstorming activity is to help the students realize the importance of the topics covered in this minilesson - sediment dispersal and continental margin stratigraphy. The hook can be used regardless if one chooses to do all or portions of this minilesson.

PART II. Sediment dispersion:

The goal of these activities are to use tidal range, significant wave height, sediment supply and shelf width data to examine the differences between the types of sediment dispersal and then to classify different riverine systems world wide as either Proximal-accumulation-dominated (PAD), Marine-dispersal-dominated (MDD), Estuarine-accumulations-dominated (EAD), Subaqueous-delta-clinoform (SDC), or Canyon-captured (CC).

A. Introductory PowerPoint: Dispersion Powerpoint (PowerPoint 2007 (.pptx) 1016kB Aug21 15)

B. Activities - NOTE: there is a activity assignment that needs to be assigned to the students prior to the class period.

  1. Create graphs to explore the relationships between tidal range, significant wave height, sediment supply and shelf width data.
  2. Predict the type of dispersal system from tidal range, significant wave height, sediment supply and shelf width data from a variety of fluvial systems.

C. Files:

  1. Student - Dispersion - Student Activity (Microsoft Word 2007 (.docx) 76kB Jan5 14)
  2. Teacher -

PART III: Shelf Sedimentation Characteristics:

The goal of this activity is to use seismic and bathymetric data to document spatial sedimentation patterns for each system. Students will use bathymetric grid data within GeoMapApp to create down-channel and cross-channel profiles at different levels within each river system. Students will be able to document areas of deep incision or broad floodplains, as well as shelf and slope morphology at the continental margins. Students will utilize high resolution CHIRP seismic data and other seismic data within GeoMapApp to examine questions related to spatial sedimentation patterns in specific river-shelf systems - the Waipaoa and the Fly systems. Another goal of this activity is to allow students to synthesize data for each river system in order to predict future sedimentation patterns given changes in one or more variables that control current shelf sedimentation development. Students will tie together the S2S concept and examine how changes in subsidence, sea level, and sediment supply will influence accommodation and in the long-term the stratigraphy of the system.

A. Introductory PowerPoint: Shelf sedimentation intro slides (PowerPoint 2007 (.pptx) 426kB Aug21 15)

B. Activities:

1. Evaluating Shelf Sedimentation Characteristics

a.Use shelf width and sediment data to examine influences of accommodation space on sediment storage.

2. Profiles

a. Use GeoMapApp to create profiles for the Fly and Waipaoa systems.

b. Students predict how changes in subsidence, sea level, and sediment supply influence shelf sedimentation distribution.

C. Files:

1. Student - Student Information (Microsoft Word 2007 (.docx) 21kB Jan5 14)

2. Teacher -

Assessment:

Instructors may choose to grade the bathymetric profiles students develop and interpret, as well as formal or informal reports on current sedimentation patterns.

Working in groups, students could develop either down or cross channel profiles at Waipaoa or Fly and the findings could be reported to the rest of the group in the form of a short group presentation. Alternatively, this activity could follow a jigsaw format, in which the members of original groups that focused on a one of the four options (e.g. cross channel at Waipaoa) are re-grouped such that each group contains at least one student from each original river system. The new groups could then be tasked with comparing and contrasting the four systems and answering related questions.

Assessment for the student's ability to predict future stratigraphy depends on how well a student understands the controls on current sedimentation and past stratigraphic development can be readily built into the activity. For example, students may be asked to predict how sedimentation and dispersal characteristics, thus stratigraphic development, will (or will not) change given specific changes in land use (e.g., opening of a mine, deforestation, development of agriculture), river engineering (e.g., building or removing dams or levees, channel straightening), tectonics (e.g., major earthquake and uplift event), and/or climate (e.g., rising or falling sea level, increased or decreased chemical weathering rates).

Teaching Notes and Tips

Part II has an optional extension exercise outlined in the teacher handout for that section that can be added on if so desired.

Assessment

A pre-module concept-map activity will both stimulate thoughts on sediment dispersal and assess existing knowledge. Summative assessment will be measured at the end of the second activity to assess the S2S concept and examine how changes in subsidence, sea level, and sediment supply will influence accommodation, and in the long-term the stratigraphy of the system.

References and Resources

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