Sedimentary Analysis of the Sag Pond at Fairfield Osborn Preserve
Project Description: In 2014, the students of Geography 317 visited the Fairfield Osborn Preserve to analyze the stratigraphy of the sag pond, located on the Rodgers Creek fault, and infer past environmental changes. Preliminary investigation showed distinct changes in soil color and texture with depth and macrofossil charcoal, suggesting changes in environment over time. We hope to correlate these changes in stratigraphy with long-term sedimentary processes resulting from mass wasting and tectonic activity.
Duration: Spring 2014
Type of Educational Activities: service-learning
Project Faculty: Michelle Goman (Geography), John-Scott Forester (Art and Art History)
Partners: Center for Environmental Inquiry, Steve Norwick Memorial Fund
- Geography 317 Lab Methods in Physical Geography- 11 students
Project Location: A sag pond is defined as a body of water that occurs in the lowest part of a depression formed either near the head scarp of rotational landslides or between two strands of an active strike-slip fault. Our site is located at 38° 20.591 N and 122° 35.460 W within the boundaries of Fairfield Osborn Preserve. The sag pond measured 25 meters in length and 5 meters in width. The sag pond was dry at the time of sampling, allowing field data collection.
Methods: Students took soil samples along a 25 meter transect laid out along the long axis of the pond. Three locations were sampled within the sag pond and a comparative sample was taken outside of the pond. At each location, an auger was used to take a 50 cm soil core. Cores were broken down into 10 cm increments for further analysis. In the field, we measured pebble size and characterized soil color using Munsell color charts. Lab analysis included texture by feel, loss on ignition, magnetic susceptibility, pH, macro charcoal and percent of clay and sand composition. Variables were plotted against soil depth (cm below surface) to determine how soil properties may have changed over time.
Field and laboratory methods were conducted under the guidance of Michelle Goman.
Results Summary: An abrupt increase in gravel content and iron-rich sediment in soils 40 cm below the surface of the sag pond suggests a mass movement event in the area, perhaps more than 100 years ago. The low amount of charcoal (a few pieces within the top 25 cm of soil) coupled with the lack of fire evidence in a nearby tree-ring study suggests that fire has not recently occurred in the area. Shells, insects, small amounts of charcoal, and seeds were found in the top 25 cm and can be made available for further analysis.
Presentations: (see data disclaimer)
- Poster: Scientific Mud Pies: Sedimentary Analysis of the Sag Pond at Fairfield Osborn Preserve. Kyle Towers, Pasha Abooamery, Emma Anthony, Gracie Lock, Mark Castro, Lauren James, Devin Connor, Chris Cunningham, Quinten Rodriguez, David Price, Justin Reacer (Advisor: Michelle Goman, Geography 317 Lab Methods in Physical Geography) Towers et al. 2014 (pdf, 1.8 Mb); 2014 WATERS Abstracts
- Powerpoint: Scientific Mud Pies: Sedimentary Analysis of the Sag Pond at Fairfield Osborn Preserve. Lauren James, Mark Castro, Justin Reacer, David Price, Quinten Rodriguez, Pasha Abooamery, Chris Cunningham, Emma Anthony, Kyle Towers, Gracie Lock, Devin Connor. (Advisor: Michelle Goman, Geography 317 Lab Methods in Physical Geography) James et al. 2014 (pdf, 2.5 Mb)