1. Structure and Sedimentary Rocks (Lab #2)

2. Fold geometry
See page 238–241 (237–240 6th Ed.)

3. Faults What’s the footwall? What’s the hanging wall?
Different types of faults
See pages 243–245 (242–243, 6th Ed.)

4. The Compass, drawing strike and dip symbols, and the Right Hand Rule

5. The compass N E W S 360 degrees = = 000 degrees = 090 degrees

6. The compass
000 or 360
090
180
270 N E S W

7. Drawing a strike and dip symbol
What is the orientation determined?
115/37 NE

8. Drawing a strike and dip symbol
115
115/37 NE 37 NE
What is the strike?
Done!
Remember that if it is a cleavage measurement,
the symbol is like this…
What is the dip direction?
What is the dip?

9. The Right Hand Rule
The Right Hand Rule is a convention that is used so that strike and dip is always written so that the dip is to the right of the strike direction.
This allows us to show strike and dip without dip direction (particularly important for computer applications).
Examples…

10. Right Hand Rule
For example, 000/49 has a strike of 000 and a dip of 49 to the RIGHT of 000 (i.e. 090, or East) like this…
000
right 49
right
180
has a dip of 49 to the RIGHT of 180 (i.e., 270 or West) like this…
But 180/49, though it has the same strike,

11. Right Hand Rule…more examples
090/37 is this… 37 37
but 270/37 is this…
045/63 is this… 63 63
but 225/63 is this…

12. Right Hand Rule…last comment
As a precaution most people continue to indicate direction of dip even when they adhere to the Right Hand Rule.
225/43 NW
045/63 SE
130/27 SW
265/12 N
315/29 SW
010/82 E
Which of these isn’t correct (i.e., doesn’t follow the Right Hand Rule)?

13. Maps and block diagrams
Map (a) on p. 4 shows geological contacts that dip away from a central point at a consistent angle.
Map (b) shows 3 geological units that dip slightly to the east. The outcrop pattern is the result of topography.

14. Maps and block diagrams
Block diagram (c) shows a folded sequence (younger beds in the middle) but with all units dipping in the same direction.
Block diagram (d) shows a plunging fold. This diagram is made harder by not showing the junction between the units on all the faces.

15. Sedimentary rocks
Supplementary information on sedimentary rocks available in Monroe & Wicander pp. 162–167 (161–165, 6th Ed.)

16. Sedimentary Rocks & Structure
Clastic — rocks made up of fragments deposited by a flowing medium (air, water, ice)
Non-clastic — rocks made from chemically or biologically derived material

17. Clastic rocks
Clastic rocks are classified according to the nature of the following components:
Grains
Matrix
Cement
Pores

18. Pores 10% pore space is not unheard of Doesn’t sound like much but…
10 km x 10 km x 10 m = 1 x 109 m3
at 10% porosity  1 x 108 m3 of pore space (oil?)
= 1 x 1011 litres
= 2.64 x 1010 US gals
= 6.29 x 108 barrels
worth $3.33 x (at $53/barrel on January 17)
That’s $33,300,000,000 (~$33 billion)!

19. Non clastic rocks Non-clastic rocks classified by composition
Carbonate
Evaporite
Biochemical
Chemical

20. Texture
Refers to the nature and inter-relationship of the constituent particles
most non-clastic rocks are “crystalline”
texture of clastic rocks described by various features

21. Clastic rock texture Grain size Roundness
Sphericity (equidimensionality)
Sorting
size
composition

22. Sedimentary structures
Primary (physical)
bedding
ripples
cross laminations
graded bedding
cracks
raindrop imprints
etc.

23. Sedimentary structures
Primary (organic)
Tracks & trails
Burrows
Bioturbation
Stromatolites (moderate scale)
Reefs (large)

24. Sedimentary structures
Secondary (physical)
Load
Dewatering (fissility, cone-in-cone)
Secondary (chemical)
Nodules & concretions
Dendrites

25. Other sedimentary features
Colour — can be loosely indicative of the environment of deposition.
Red (hematite) indicates subaerial deposition
Black (carbon) indicates reducing environment
Maturity — chemical stability and degree of sorting of components indicating distance of transportation from source area.

26. Last exercise
Apply the revised sedimentary rocks information to a suite of 5 rocks found in the 6 drawers at the back of the lab labeled rock and fossil samples (not those in the benches)

27. To make the lab go more smoothly…
Because of the number of people and the small numbers of samples at the back of the lab, it would help if some people started with the Sedimentary Rocks part of the lab (Part IV, p. 5) first and do the Structure parts (Parts I, II and III) later.

28. Questions?