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).

As a learning exercise you could lave also filled two tables, pages 22 and 26, from chapter 3 in your lab manual. 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.

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