NAME:

ID#: University of Alberta

EAS 421 STRUCTURAL GEOLOGY Hand in all pages

LAB EXAM REPRESENTATIVE QUESTIONS

Ensure that all constructions are provided and derivation of results is explicit. Use coloured pencils where appropriate in diagrams, and use labels where needed (if in doubt - label it). The sample for part D will be available for 20 minutes only. Begin part D as soon as the sample arrives at your desk.

A. NET PROBLEMS (value 30%)

1. In an area of poorly exposed and uniformly dipping sandstone, three drill holes are placed to determine the subsurface attitude of bedding. From the data given, determine the attitude of bedding.

Drill hole no.Trend PlungeCore to bedding-normal angle

1200 40 50

2090 50 35

3298 5885

2. One limb of a parallel fold strikes 033, is overturned and dips 70 toward the northwest. The horizontal projection of a mineral lineation in this limb trends 013. If the lineation formed before the fold, what this the trend and plunge of the lineation in the other limb of the fold, which strikes 348 and dips 15 SW?

3. A fault has an orientation of 030, 45 SE. Beds on the northwest side of the fault dip 35 toward 350. Beds on the southeast side of the fault dip 17 toward 320. Assuming that the beds on the northwest side have the same attitude as before faulting, what is the rotational movement of the fault (the angular amount and sense of hanging wall rotation relative to the foot wall)? Hint: rotate fault to horizontal, then measure the difference in strike of the bedding normals transferred to the periphery of the net.

B. FAULT DISPLACEMENT (value 30%)

A fault strikes 090 across a map area with poor exposure and dips 55 N. The bedding in the host rock strikes 010 and dips 45 SE. A dyke strikes 315 and dips 65 SW. A vein strikes 325 and dips 70 SW. A thin distinctive black limestone bed occurs in the host rock. The data are as follows; distance is measured toward the east from zero.

Distance onDistance on

North wallSouth wall

Limestone0150 m

Dyke250 m200 m

Vein350 m(?)

Determine the trend, plunge, rake and value of the net slip, and the relative movement of the fault blocks. Draw a map showing the limestone marker and the dyke and the location of the vein on the south side of the fault.

C. FOLD ANALYSIS (value 20%)

Figure 1a is an oblique perspective view of a small map area showing several outcrops, some with asymmetric folds. Each outcrop is represented on the map view (b) beneath by a strike-and-dip symbol or a trend-and-plunge symbol. The black layers represent thin limestone beds within shale. The limestone bed at one outcrop is not necessarily the same bed as at adjacent outcrops.

1. Using the appropriate map symbols for asymmetric minor folds as viewed down plunge, indicate the fold asymmetry on map(b).

2. Draw in the principal fold axial traces on map (b).

3. Sketch structure section A - A= along profile (c), inferring folded layers both above and below line A - A; show parasitic folds schematically.

D. TECTONITE DESCRIPTION (value 20%)

Describe with the aid of a diagramall the structures and fabric elements you can see in the tectonite sample. Provide possible genetic relationships between structures (i.e., relative timing and possible derivation from the same or different deformation episodes).