Fold mapping lab

Undergraduate, senior-level structural geology course, required for majors.

Students should have been introduced to the concepts of axial planar cleavage development, fold geometry, bedding-cleavage relationships, and parasitic folds. This activity gives the students practice in applying these concepts to map a regional fold structure.

This activity is part of a segment about 3/4 of the way through the semester in which we discuss cleavage development, fold geometries, and applications of outcrop- to regional-scale mapping.

Measuring attitudes of lines and planes with a Brunton compass

Taking detailed field notes of lithologies and structures

Integrating field data to inform an interpretation of regional structures

Drawing an interpretive cross section based on field data

Working in groups
using a Brunton compass

For this activity, you will need to have several (5 is a good number) samples showing bedding-cleavage relationships where the angle between bedding and cleavage is different in each sample (higher S0-S1 angles in the hinge zone, lower on the limbs). You will also need samples of parasitic folds (I don't worry about matching the lithologies because I'm not lucky enough to have samples that match and ask the students to only write notes on the lithologies of the S0-S1 samples). You will need to arrange the samples around the room such that the student can make a strip map of bedding and cleavage, and note the vergence of parasitic folds. I affix the samples to the tables using modeling clay, but I still have the tell the students to gingerly measure attitudes because the samples can move. Attached are the activity instructions and a sample strip map and cross section.

Fold Mapping Activity (Acrobat (PDF) 623kB Apr30 12)
Strip map and X-section sample (Acrobat (PDF) 104kB Apr30 12)

Excellent teaching samples can be collected in the PA, VT, or other slate belts where cleavage and bedding are still distinguishable.

I grade students' maps, x-sections, "field" notes, and setreographic analyses using a 0-5 rubric for each component.