TAKING THE MYSTERY OUT OF COMPLEX GLACIAL SEQUENCES AT ENVIRONMENTAL AND GEOTECHNICAL SITES IN THE MIDCONTINENT:
Part 2: Understanding the Effects of Post-Depositional Weathering – Development of Surficial Soils, Weathering Zones, and Secondary Jointing

Surficial weathering alters the geotechnical and hydrogeologic properties of glacial sediments. South of the Canadian Shield, where glacial deposits are derived from Paleozoic and younger sedimentary bedrock, distinctive weathering patterns and weathering zones develop from the surface downward.

Surficial soils develop from the land surface downward and are commonly 0.5 to 2 m (1.5 to 6 feet) thick. Alteration is so great that these surficial soils have a pervasive secondary soil structure that largely obliterates any primary sedimentary structure.

Beneath the surficial soils, weathering continues but is not as intensive, and a sequence of “weathering zones” develop. These zones are defined on the basis of

• Color-related oxidation state
• Carbonate status (leached or unleached)
• 3Presence of absence of jointing

The sequence and depth of these weathering zones indicate the nature and extent of the subsurface alteration that these deposits have undergone.

Weathering zones can be quickly and readily described using simple letter abbreviations, and are extremely important in depicting the weathering changes that have taken place to different units in the glacial succession.

Accompanying weathering is the development of secondary jointing: fractures that affect infiltration and sediment strength. Examination of fracture geometry indicates that they develop from desiccation. Although there is still much research to be completed, the desiccation process significantly affects the hydraulic conductivity of fine-grained glacial deposits.

What does taking the mystery out of weathered glacial deposits require? An understanding of surficial soils, weathering zones, and secondary joint development. This webinar, Part 2, provides techniques for identifying and understanding weathering zones and the occurrence of secondary jointing. Join us for this webinar and learn how to take the mystery out of the complex glacial sequences underlying your environmental and geotechnical sites.

This webinar is the second part in a Three Part Series in characterizing complex glacial sedimentary successions. Register for all three and receive a special reduced rate along with complimentary field tools by Midwest GeoSciences Group.

Pay one site (one computer) registration fee and an unlimited number of participants from your organization can attend at that site.

Participants will receive a handout referencing the webinar topics and discussion.

1.5 Professional Development Hour (1.5 PDH) for each verified attendee will be available as a Course Completion Certificate from Northern Illinois University.

Register by 25 March 2010 for this three part webinar series and receive 3 free FIELD GUIDE FOR SOIL AND STRATIGRAPHIC ANALYSIS, 3 free USDA SOIL TEXTURING FIELD FLOW CHARTS and 3 free GLACIAL SEDIMENTS CHARTS (12" X 18") by Midwest GeoSciences Group.

Register for this webinar (without the other in the series) and receive 1 free FIELD GUIDE FOR SOIL AND STRATIGRAPHIC ANALYSIS by Midwest GeoSciences Group.

Additional field guides and flow charts may be purchased for a reduced price with early registration (see registration form for details).

Attendees will be invited to actively participate during this live and interactive on-line web seminar. Discussion is planned following the webinar for those who want to continue the session. Bring your questions to the webinar and present them to the instructor and other participants for exploring the best solution.

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Instructor Bio
Tim Kemmis received his bachelor’s degree in agricultural soil science from the University of Illinois and his master’s degree in glacial geology while working as a graduate assistant at the Illinois State Geological Survey.

He worked 14 years for the Iowa Geological Survey, during which he received his Ph.D., and where he:

• Carried out glacial sedimentologic investigations
• Remapped the Des Moines Glacial lobe
• Established the formal glacial stratigraphy for the lobe based on depositional environments
• Discovered a new type of hummocky glacial topography
• Determined the geometry and origin of jointing in glacial tills
• Developed a lithofacies code to decipher the history of glacial outwash and alluvial sequences

For most of the time since 1992, Tim has worked as a senior geologist consultant and project manager for large-scale hydrogeologic investigations. His unique experience as both an applied researcher and consultant has allows Tim to effectively unravel sedimentary complexities coupled with his personal ability to teach these concepts to all staff levels.