In the southeastern fault block of the Bree Creek Quadrangle, Paleozoic rocks have experienced two episodes of folding, F₁ and F₂. The foliations shown on the Bree Creek map are axial planar. F₁ parasitic folds are indicated by the symbol with a singleheaded arrow, and F₂ parasitic folds are indicated by the symbol with a double-headed arrow.

1. On your Bree Creek Quadrangle map draw the axial-surface traces, S₁ and S₂, for both generations of folds, as is done in Fig. 8.7, using the parasitic folds to help you locate them. Use appropriate symbols to indicate synclines and anticlines.

2. Draw structure sections C–C’ and D–D’, using the axial-planar foliations to help you determine the attitudes of the axial planes of the folds.

Because structure sections C–C’ and D–D’ are intersecting vertical planes, they have a common vertical line. Draw this vertical line on both structure sections and label it ‘‘Intersection of C–C’ and D–D’.’’ The depth from the surface to the top and bottom of each rock unit must be the same along this vertical line on both structure sections, as if you had cored down at this spot on your Bree Creek map and shown the data from the core on both structure sections. After you have drawn structure section D–D’, the depth and thickness of each rock unit on this line of intersection can be transferred to your C–C’ topographic profile, thereby providing stratigraphic control for your C–C’ structure section.

3. Completely and succinctly describe each generation of folding. Include attitudes of the fold axes, attitudes of the axial surfaces, interlimb angles, symmetry, fold class, age of folding, and type of interference pattern.

Transcribed Image Text:

a → S1- S1- S1- S1-