Role of Sedimentation in Rifting

Becky Dorsey, Sue Cashman, Scott Bennett, Jack Loveless, Lisa Lamb, Andrew Goodliffe

Summary

This is one component of the Rupturing Continental Lithosphere suite of mini-lessons.

The Sedimentation module will build directly on the introductory Bathymetry of Rifted Margins Lab, and includes material for one lecture/activity - a powerpoint lecture with an embedded set of problems for students to work out and discuss. Students work with basic equations, and analyze/discuss simple solutions.

This mini-lesson focuses on examining the role of sedimentation, and how it can influence the development of rifted margins over time. Students solve a series of problems investigating the isostatic effect of filling a basin with water and sediment using examples - Gulf of California basins - studied in previous mini-lessons (Bathymetry of Rifted Margins, Extensional Styles). Students then examine how crustal thinning affects the depth of sedimentary basins. In the final part of the mini-lesson, students are asked to determine one or more sets of rifting parameters (initial crustal thickness, initial thickness of mantle lithosphere, density of sediment fill) that could give rise to observed characteristics of the Delfin Basin.

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Learning Goals

Overarching Take-Away: students will learn that sediments are not just a passive record of past processes and environments, but in some settings they play an active role in structural deformation, crustal extension, and rupturing of the Earth's lithosphere. Students will:

  • Predict isostatic response of crust to water and sediment loading
  • Apply principles of isostatic loading to Gulf of California examples
  • Calculate possible starting conditions that could generate observed crustal architecture in the Gulf of California
  • Examine how sediments control parameters of rifting, such as heat flow, time to continental break-up, crustal recycling, and architecture of rifted margins

Skills to be developed include: critical thinking, data analysis, learning to develop simple analytic solutions to predict basin subsidence, and synthesis of data with new understanding of regional crustal processes. Students will demonstrate these skills by solving problems, by writing/reflecting on problem design, and by small group discussions moderated by instructor.

Context for Use

This activity is designed for use in an upper-level undergraduate or graduate course in tectonics, stratigraphy, sedimentation or basin analysis. The lesson is designed to give students an understanding and working knowledge of principles of sediment mass balance and basin filling, isostatic balance, and the influence of sediments on parameters of rifting such as crustal recycling and architecture of rifted margins.

The activity can be used in two one-hour lecture classes, with the possibility of assigning some problems as homework to be completed between classes and discussed in the second class. Alternatively, the activity could be used in a three-hour lab class.

Description and Teaching Materials

Students use measurements and observations from the Gulf of California Bathymetry of Rifted Margins Lab to solve isostasy problems based on Gulf of California sedimentary basins. The activity consists of a powerpoint lecture Role of Sedimentation in Rifting (PowerPoint 2007 (.pptx) 3.6MB Oct7 15) with embedded problems that individual students or small groups of students will solve and discuss in class before moving on to subsequent problems.

Teaching Notes and Tips

"Notes to Instructor" Notes to instructor, "Role of Sedimentation" mini-lesson (Microsoft Word 2007 (.docx) 100kB Aug19 14) introduces the sequence of materials and activities in the "Exploring the role of sedimentation in continental rift systems" module.

The "Advanced optional problems" spreadsheet

enables the instructor to test many different possible solutions to an optional further investigation of the final problem in the "Isostasy in Basin Analysis" lecture and problem set.

Download Teaching Notes and Tips (Microsoft Word 2007 (.docx) 100kB Jan21 15)

Assessment

  1. Students solve problems similar to the ones learned in class or lab but with different starting values.
  2. Students design a way to solve for rifting parameters that could give rise to observed crustal architecture, or students write a short reflection piece on the influence of sediments on rifting.
  3. Students demonstrate grasp of material through small group discussion moderated by instructor.

In addition to assessment specific to this mini-lesson, several synthesis test questions probe students' cumulative learning of the physical characteristics of the Gulf of California and the processes that have shaped it.

Instructor Stories

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References and Resources

  • Bialas, R. W. and W. R. Buck, 2009, How sediment promotes narrow rifting: Application to the Gulf of California: Tectonics 28(TC4014, doi:10.1029/2008TC002394).
  • Dorsey, R.J., P.J. Umhoefer, M.E. Oskin, and R. Arrowsmith, 2013, Rupturing Continental Lithosphere in the Gulf of California and Salton Trough: GeoPRISMS Newsletter no. 30, p.1-6.
  • Lavier, L. L. and M. S. Steckler, 1997, The effect of sedimentary cover on flexural strength of continental lithosphere: Nature 389: 476-479.
  • Martin-Barajas, A., M. Gonzalez-Escobar, J.M. Fletcher, M. Pacheco, M. Oskin, and R. Dorsey, 2013, Thick deltaic sedimentation and detachment faulting delay the onset of continental rupture in the Northern Gulf of California: Analysis of seismic reflection profiles: Tectonics, v. 32, issue 5, p. 1294-1311.

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