INQUIRY-BASED TEACHING OF SEQUENCE STRATIGRAPHY USING THE “DELTA-BOX”

The National Center for Earth surface Dynamics' (NCED) “Delta Box”, which was presented to attendees of the Cutting-Edge Program's workshop on “Teaching Sedimentary Geology in the 21st Century”, was built and used to teach principles of sequence stratigraphy during part of a Sequence and Seismic Stratigraphy course. Previously, these principles were taught using the conventional lecture approach with exercises that were completed outside of class. There was limited student engagement during class and little inquiry-based learning by the students.

Using the “Delta Box”, students are able to derive the relationships between stratal geometry and variation in base level, sediment supply and tectonics. Initially students held sediment supply and water discharge constant and did not alter the tilt of the box (a simulation of tectonic uplift or subsidence). Base level was altered during this simulation. Students attempted to alter base level in a sinusoidal manner and used a ruler and stopwatch, while working in teams, to measure the amplitude and rate of base level change. As base level changed, they documented direction and rate of migration of the offlap break, style of offlap, position of onlap and downlap and made estimates of the partitioning of fine and coarse facies (coal-dust and sand are the proxies for these facies in the model) along the depositional profile. They compare data on rate and amplitude of base level change with the data on concurrent variation in stratal geometry and write their own set of principles that describe the relationship between stratal geometry and base level change. They then can perform similar experiments holding base level and “tectonics” constant while varying sediment supply (but holding water discharge constant) and then hold sediment supply constant and vary water discharge to assess the impact of climate variation. Next, they can vary “tectonics” by gradually altering the tilt of the “Delta Box” using wedges, while holding the other variables constant and to assess the impact of tectonics. They then compare the impact on the stratal geometry caused by variation in each variable; consider where and over what intervals each variable is most likely to be dominant. Finally, students consider the strengths and weaknesses of the simulations, how well they represent nature and how this may impact their “principles.”