Well Core Analysis: Capstone Activity for Historical Geology
As a capstone laboratory project for introductory historical geology, the class is divided into groups of 3 to 5 students to analyze a sedimentary rock core and associated geophysical log. Each group graphically describes and interprets 24 feet of split core, along with a gamma log for the same interval. The class is provided with hand lenses, binocular microscopes, , spray wash bottles, dilute HCl, a logging form, and with selected research papers on textures, structures, and fossils found in the core, regional paleogeography, and on the tectonics and paleooceanography at the time of deposition. Each group gives a 15-minute presentation of their core interval to the entire class and submits a graphic log for the interval. All students submit a two-page report summarizing their own observations and interpretations of the core interval. Assessment is based on a combination of the group presentation and individual report.
Context for Use
- A freshman-level introductory course in historical geology at either a 2-year or 4-year college
- An undergraduate- or graduate-level stratigraphy or sedimentology course
Students should have completed previous laboratory or field exercises on the identification and interpretation of sedimentary rocks, sedimentary structures, and fossils.
Total laboratory time is 6 hours with the core available for student use outside of the scheduled class time in a 4-hour open laboratory session.
A well core for this exercise might be obtained from an oil or mining company, or through a state geological survey. College alumni working for energy or mining companies, consulting firms, or government agencies may be able to arrange for donation of part of a core to the college. The U.S. Geological Survey Core Research Center in Denver (http://geology.cr.usgs.gov/crc) is also a potential source of information on well cores.
This exercise could be modified to use well cuttings, instead of core, with more emphasis on textural trends, mineralogy, and possibly microfossil identification.
Description and Teaching Materials
Lab 1 (1.5-hr) – introduction to subsurface methods, including constructing graphic well logs and interpreting geophysical logs; Orientation to well core (e.g. labeling, marks indicating orientation of core, depth measurements on core box, markings produced in coring and preparation of core) and geophysical log.
Lab 2 (1.5 hr) – safety briefing followed by selection of groups; each group begins description of two boxes of core, each with 9 feet of split core; Emphasis is on learning to use the logging form and describing the "big picture" for the entire 18-feet of core; Professor acts a consultant to guide students in observing and interpreting textures, grain-size trends, structures, fossils, and minerals. Students are offered a selection of photocopied research papers that can borrowed and read before the next lab session. Other references are included as *.pdf files on Blackboard.
Lab 3 (1.5 hr) – completion of core description and preparation for group presentation; Professor continues role as a consultant using the Socratic method to guide observations and interpretations.
Lab 4 (1.5 hr) – each group gives a presentation to the entire class gathered around the group's boxes of core. Each group has 10 minutes for a presentation and 5 minutes for questions. The professor summarizes and adds to each group's presentation once it is complete. Students submit individual 2-page papers on their core interval.
Equipment and supplies
Dilute hydrochloric acid in a dropper bottle (1 per group)Photocopied (or *.pdf copies) of references containing illustrations and interpretation of body and trace fossils, sedimentary structures, plate tectonics, paleogeography, paleoclimatology, and paleoceanography (if applicable) help students place the core in a local, regional, and global context.
Hand lenses (1 per student)
Meter sticks with a scale in inches (1 per group)
Plastic spray bottles with water (identical to those used for misting plants - 1 per group)
Binocular microscopes (optional - 1 per group)
Teaching MaterialsStudent Handout for Well Core Project (Microsoft Word 304kB Jun11 10)
Graphic Logging Form (Microsoft Word 242kB Jun11 10)
Teaching Notes and Tips
References and Resources
Swanson, R.G., 1981. Sample examination manual: Tulsa, OK, American Association of Petroleum Geologists Methods in Exploration Series.Standard symbols for graphic logs
Nilsen, T.H., Lindquist, T. and Cobb, J.C., 2006. Lithologic patterns for stratigraphic columns and cross sections, in Walker, D.J. and Cohen, H.A., eds. The geoscience handbook, AGI data sheets (4th edition), p. 42-44.Interpretation of wireline geophysical logs
Bohling, Goeff, and Doveton, John H., 2002 Reading the rocks from wireline logs: Lawrence, KS, Kansas Geological Survey, updated 2003 - online tutorial and software at http://www.kgs.ku.edu/PRS/ReadRocks/portal.html
Doveton, John H., 1994. Geologic log interpretation: Tulsa, OK, Society of Economic Paleontologists and Mineralogists Short Course No. 29, 169 p. [ http://scnotes.sepmonline.org/content/sepscgli/1.toc]
Lewis, D.W., 1984. Practical sedimentology: Stroudsburg, PA, Hutchinson Ross Publishing Co., 227 p.
Interpretation of trace fossils in core
Chamberlain, C. Kent, 1978. Recognition of trace fossils in cores, inBasan, Paul B., ed., Trace fossil concepts: Tulsa, OK, Society of Economic Paleontologists and Mineralogists Short Course No. 5, p. 133-183. http://scnotes.sepmonline.org/content/sepsctfc/1/SEC5.body.pdf