Sediments and carbon burial on the continental margins


Summary

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

This lesson will explore the factors that control the character and fate of organic carbon delivered by rivers from the continents to the oceans. A Powerpoint presentation and in-class discussion is used to introduce the students to aspects of carbon cycling in sedimentary systems, with particular focus on the sources of particulate organic carbon discharge from rivers to the continental margins. Students will then complete a homework assignment in which they plot data on carbon burial efficiency on various continental shelves and answer questions about the possible controls on differences amongst systems. A guided in-class discussion would explore the implications of variations in carbon burial on margins over space and time.

Learning Goals

  • Students will be able to describe the role of source-to-sink sedimentary systems in the global carbon cycle
  • Students will be able to predict which continental margin environments might be characterized by the highest organic carbon burial efficiencies
  • Students will be able to articulate the possible effects of climate change and human perturbations on sedimentary systems (e.g. construction of dams) on carbon burial on the continental margins.

Key concepts:

  • Most of the organic matter produced on land or the ocean is degraded (not buried).
  • The small fraction that is buried over the long term has a key control on atmospheric chemistry and climate, and is the precursor to petroleum.
  • The carbon carried by rivers includes fractions of different age and reactivity such as recent plant debris, aged soil, and ancient rock carbon.
  • The composition of what emerges into the coastal ocean strongly reflects the properties of the watershed (including its tectonic setting)
  • Rapid sediment burial favors high organic carbon burial efficiency.

Context for Use


Upper level undergraduate courses in sedimentology/stratigraphy, marine geology, low temperature geochemistry

Students should have an understanding of the differences between active and passive margins, the short and long term carbon cycles, and radiocarbon (14C) dating

Along with introductory and follow-up discussions of the material, this lesson could occupy one to two class periods and a homework assignment.

Description and Teaching Materials

This module consists of the following components:

1) An introductory lecture (PowerPoint 2007 (.pptx) 3.6MB Sep10 15) on the role of margins, especially river-dominated margins, in the carbon cycle. Questions for break-out discussions during the lecture are included

2) A homework exercise in which students plot and describe data and then consider its implications.
Carbon Burial on Continental Margins-- Controls from Source to Sink (Microsoft Word 2007 (.docx) 564kB Nov14 13)

3) A guided discussion of the homework results and discussion of potential influences of tectonics, climate change, and humans on organic carbon burial.

Assessment

The students will complete a homework exercise. Exam questions will be used to assess their synthesis of the lecture material, discussion, and homework.

References and Resources

  • Berner 2003 Nature- The long-term carbon cycle
  • Blair and Leithold
  • Hossler, K., and Bauer, J.E.,2013, Amounts, isotope character, and ages of organic and inorganic carbon exported from rivers to ocean margins: 1. Estimates of terrestrial losses and inputs to the Middle Atlantic Bight: Global Biogeochemical Cycles 27, 1-16.
  • Griffith et al., 2010

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