Geol 5, Lab #3: Sedimentary Rocks under the Microscope

For this lab you were required to answer all questions of page 21 (ternary diagram for classification of sandstones) and to fill two tables,pages 22 and 26, from chapter 3 in your lab manual. The ternary diagram exercise was done collectively in the classroom and your answers should match the key below. The first of two tables, Table 3.1, page 22, dealt with sandstone textures. You were required to answer only questions 2, 3, 4, and 5 for all three samples A, B, and C from Figure 3.7, p. 23. The second table, Table 3.3, page 26, dealt with carbonate rocks textures. You were required to answer all questions, 1, 2, 3 4, 5, and 6 for all six samples from Figure 3.9, page 25. You were ALSO required to provide a rock name following Dunham's and Folk's classifications. What follows is a key to this lab.

You will not be graded on Dunham's or Folk's names, but make sure to double check what you put down in your exercise.

Sandstone ternary diagram, page 21

Composition of point B

Composition of point C

Composition of point D

Composition of point E

% of Quartz

40

30

70

60

% of Lithic Grains

40

60

0

20

% of Feldspar

20

10

30

20

Table 3.1, page 22

Question #

Rock A

Rock B

Rock C

1

skip

skip

skip

2

a

a

b

3

a

c

d

4

b

d (a+b)

d (a+c)

5

a

b

c

Table 3.3, page 26

Question #

Rock A

Rock B

Rock C

Rock D

Rock E

Rock F

1

c

b

a

a

a

a

2

b

c

c

c

c

a

3

b

b

a

b

n/a

n/a

4

a

b

b

b

c

a

5

a

a

a

a

a

c

6

a

b

b

a (or b)

c

c (possibly a)

DUNHAM'S
CLASSIFICATION

MUDSTONE

WACKESTONE

GRAINSTONE

GRAINSTONE

GRAINSTONE

Dolomite indicates a DOLOSTONE,
which can not be classified according to Dunham's

FOLK'S
CLASSIFICATION

BIOMICRITE

BIOSPARITE

OOBIOSPARITE

OOBIOSPARITE

BIOSPARITE

Dolomite indicates a DOLOSTONE,
which can not be classified according to Folk's