Glacial Geology
Subglacial Module - Week #6, 1999
Objective:
Hone Field Observation, Interpretation, and Reporting Skills
Background:
Subglacial processes produce some of the most complex sediments we can deal with. Thus, they offer the best chance to assure we can make subtle separations in the field. Till is an overused word, here we restrict it to "those sediments deposited directly by glacial ice with no significant reworking". Diamictons are sediments with a wide range of grains sizes, but this term carries no genesis implication. These definations took over ten years to sort out. Tills are problematic because the processes that emplace them overlap. Basically, we have four choices (see figure)- All processes on the top plane can occur in the subglacial setting whereas the flowtill processes are more common in the ice-margin or superglacial setting. This is just a first order rule of thumb.
More detailed information can be found in the readings.
Resources:
Be familiar with sections 5.5-5.7, 10.1-10.3, and 11.2 in Benn and Evans.
Handouts:
Tasks:
NOTICE- All context on this page supercede those on the attached pages. (The others are older versions)
1. Decide how to describe diamictons so that you will have the information needed to distinguish between the three types. You will be recording part of what you need on the data sheets, but you will need to develop a check list covering any additional important properties of diamictons.
2. Expose a ~meter wide swath of the outcrop.
3. Using your check list describe the exposed diamictons at the site. Record all properties as well as take sketchs of the geometry of any units and lots of photos!
4. From your descriptions, make an educated guess as to the origin of these three deposits. Hint: it may be that one or more of the units is neither a lodgement nor a meltout till. In this case simply say so. Support your interpretation.
5. Make a report - This will have a scientific format (similar to the papers we read last week), thus the data sets need to be detailed and complete. Moreover the background sections should include all important references. Figures are essential - (for overall location, outcrop geometry and outcrop details) (For this week we can restrict ourselves to raster formats).
SEE Special Note
The completed report (in HTML format of course) and all necessary files should be in a folder with your first name and the starting file should be called index.html.