SEDIMENT ANALYSIS

Objectives:

• Determine the rock and mineral characteristics of the bottom and banks of the wetlands using methods that are reliable, reproducible, and accurate.
  
• Present the determinations of the rock and mineral characteristics in a scientific format.
  
• Determine the local and regional geology through literature research.
  
• Derive conclusions regarding the geology of the wetlands from core and dredge samples taken from the wetlands natural laboratory.
  
• Design a site sampling approach that allows for the successful completion of objectives.
  
• Design a sample analysis protocol that allows for successful completion of objectives.
  

Logistics:

• Students who participate in the geology module of the wetlands study do so as a component of their Physical Geology Laboratory class, GLY 1010L. The GLY1010L Laboratory exercises that cover sediments and sedimentary rock accommodate the geology module of the wetlands study.
  
• Because the students in the GLY1010L are also enrolled in the lecture, the students have a basic understanding of several of the geologic processes pertinent to the module in order to approach the objectives outlined above.
  
• All of the students in the lab (20 students for 2 hours) participate in determining the site sampling program and sample analysis protocol. Final plan is given a go ahead by the instructor. This takes place after taking the students on a familiarization tour of the wetlands. (During plan determination a map of the site is needed and appropriate sampling gear should be discussed and made accessible to the student).
  
• Students pick or are assigned a partner, as well as a sampling location in the wetlands. Each student team will sample the wetlands with a box core, dredge, sandpoint, or auger type core, depending on the site characteristics.
  
• Students return with samples to be identified the next time the GLY1010L lab meets.
  
• Student teams complete a final report in which they have determined the sediment characteristics of their sample.
  
• Student teams discuss their findings with each other and determine how the geology of the wetlands relates to the local and regional geology.
  

Parameters to be analyzed:
The following field sampling gear and field analysis instruments are available for the students: Auger corer, sandpoint corer, piston corer, box corer, bottom dredge, PVC pipe, rock hammer, sledge, containers, field microscopes, rock and mineral identification kits. Rock and mineral identification kits contain hydrochloric acid, nail, copper penny, glass plate, porcelain streak plate, magnet, pocket knife, hand lens, grain size comparison cards, and a comprehensive rock and mineral identification handbook. Cores, dredge, and field microscopes can be purchased from Wildlife Supply Company, 1-800-799-8301 or web site at www.wildco.com. Rock and mineral identification kits can be assembled from material purchased through Fisher Scientific.
Time and sample type determines the type(s) of parameters measured. In general, the laboratory can accommodate the following analysis at this time:
Quantitative Analysis:

1. Grain Size Analysis (sieving with sieve set and sieve shaker; weighing to get weight percent data)
   
2. Grain Size Analysis (Emhoff Cones for settling and sorting to derive grain size and %volume data. Sieves and Emhoff Cones can be purchased from Fisher Scientific.
   

Qualitative Analysis:

1. Grain composition (visual, using binocular stereo microscopes, and rock and mineral ID kits).
   
2. Determination of terrigenous, biogenous, and authigenic components.
   
3. Particle shape and roundness can be visually estimated and used to determine the degree of transport and reworking of the sediment grains
   
4. Fossil identification of both macro and microfossil can be accomplished; lab equipped with transmitted light microscope (Olympus BX-40, phase contrast stage and polarizing filters) as well as a digital imager (Pixar Digital Camera 1.3 Megapixel) with output to a computer for microscopic grain determinations.
   
5. Students also visually qualitatively estimate the porosity, permeability, color, induration, of the whole rock/sediment sample.
   

Statistical Data Analysis:
Statistical analyses are performed on the measured grain size data to arrive at a conclusion regarding sediment sources, transport history and type, and site-specific processes. All data are entered on a Microsoft EXCEL spreadsheet and then imported into KALEIDOGRAPH by Synergy Software, a graphing and statistical analysis program. Methods of Grain Size Analysis include:

1. Graphical plots:
   
2. Individual weight percent plotted as a function of grain size to create a grain size histogram that provides a quick and easy pictorial for representing grain size distributions. The approximate average grain size and sorting, in other words the spread of grain size values around the average size, can be seen at a glance.
   
3. Grain size frequency curves are constructed by plotting grain size against cumulative weight percent frequency. The shape of this curve is independent of sieve size.
   
4. Skewness, or the asymmetry of a frequency curve, and kurtosis, the peakedness of a frequency curve, can be used to quantify various trends in grain sorting.
   
5. Mode size, mean size and median sizes of the grains are calculated.
   
6. Sorting, or the range of grain sizes and also the spread/scatter of grain sizes around the mean size can be estimated visually, or calculated using standard deviation. Methods of grain size analysis and the mathematical treatment of the grain size data are discussed in detail in Principles of Sedimentology and Stratigraphy, 2nd Edition, Sam Boggs Jr., Prentice Hall, 1995, pages 84 - 101. A high school or college level project facilitator can easily understand these methods.
   

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This material is based upon work supported by the National Science Foundation under Grant No. 9653672. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.