Rock formation and deformation - Fundamentals of the Physical Environment - page 265

(a) (b)

CLAY CARBONATE

Limestone

Clay

Arenaceous
limestone

Argillaceous
limestone

80 20

Sandy
silty
clay

50 50 50 50

Calcareous
sandstone

Calcareous
shale

Silty
clay
sand

Sandy
clay
silt

20 80

Sandstone Shale

Sand Silty sand Sand silt Silt

Argillaceous
sandstone

Arenaceous
shale

QUARTZ CLAY

SAND SILT

80 50 20 50

(c)

0.002 0.006 0.02 0.06 0.2 0.6 2 6 20 60 200 mm

FINE MEDIUM

SAND

COARSE FINE MEDIUM COARSE FINE MEDIUM COARSE

COBBLES
BOULDERS

BSI SAND GRAVEL

V. FINE FINE MED. COARSE V. CO.

USDA SILT GRAVEL

SAND

2 6 20 60 200 600 2000

Figure 12.9 Some standard schemes for classifying sedimentary rocks (a) by particle size and (b) by mineral content; the
numbers are percentages. (c) Below these ternary diagrams the British Standards Institute and the US Department of Agriculture
define particle size and their millimetre and micron size ranges.

6285&(52&.

WEATHERING
PROCESS

Physical Physico-

chemical

Chemical
(solution, etc.)

Biological

WEATHERING
PRODUCT

Rock
fragments

Sand
grains

Clay minerals
(mostly new
species)

Carbonate,
silicate,
chloride and
sulphate solutions

Organic
tissue

Dead
organisms

UNCONSOLIDATED
SEDIMENT

Gravel,
boulders

Sand Mud Precipitates

mineralized
skeletons

LITHIFIED
ROCK

Conglomerates
and breccias

Sandstones Shales Limestones,

cherts

Peat,
lignite, coal

Evaporites
(rock salt,
gypsum etc.)

Figure 12.10 Origins and classification of the principal sedimentary rocks.
Source: After Newton and Laporte (1989)