Download SEDIMENTARY ROCKS

CHAPTER 6.3
SEDIMENTARY ROCKS
SEDIMENTARY ROCKS
95% OF EARTHS CRUST IS IGNEOUS ROCK, AND 4-5% IS
SEDIMENTARY AND METAMORPHIC ROCK
SEDIMENTS – ANY SUBSTANCE THAT SETTLES OUT OF A
FLUID
• Created by weathering and erosion
WEATHERING – THE PROCESS BY WHICH ROCKS ARE
BROKEN UP INTO FRAGMENTS
MECHANICAL, CHEMICAL AND BIOLOGICAL
EROSION – THE REMOVAL AND TRANSPORT OF EARTH
MATERIALS BY NATURAL AGENTS
LITHIFICATION – PROCESS BY WHICH MATERIALS BECOME
ROCK
ORIGIN OF SEDIMENTS:
1. CLASTIC – ROCK FRAGMENTS FORMED BY
WEATHERING/EROSION OF EXISTING
ROCK
DEFINED BY SIZE SMALLEST TO LARGEST
CLAY, SILT, SAND, GRAVEL
Clastic sediments are often sorted by water
action before pressure and mineral cements
turn them into rock.
LITHIFICATION OF CLASTICS:
a.) CEMENTATION DISSOLVED MINERALS
THAT BIND PARTICLES TOGETHER
SILICA – FROM QUARTZ. GRAY OR WHITE
LIME – FROM CALCITE. GRAY OR WHITE
IRON – VARIOUS IRON MINERALS RED,
BROWN, YELLOW
b.) COMPACTION – PRESSURE OF
OVERLYING MATERIALS LITHIFY DEPOSITS
1. A river moves sediment into a lake.
2. Particles are sorted by size.
The largest gravels are the first
to be deposited, followed by
sands, and then silt and clay.
Sands and
Gravels
Sands
Silt and
Clay
3. Over time,
the sediments
are buried,
compacted,
and may be
cemented.
Conglomerate
Sandstone
Shale
CLASTIC SEDIMENTARY ROCKS:
CONGLOMERATE – CEMENTED MIXTURE OF
ALL SIZES OF CLASTIC MATERIALS.
LARGEST PEBBLES (QUARTZ)
SANDSTONE – CEMENTED QUARTZ /
FELDSPAR GRAINS
SILTSTONE – SILT SIZED PARTICLES
SHALE – COMPACTED SILT OR CLAY. OFTEN
OCCUR IN FLAT SHEET LIKE LAYERS.
SANDSTONE
CONGLOMERATE
SILTSTONE
SHALE
2. CHEMICAL SEDIMENTARY ROCKS – SEDIMENTS
THAT FORM FROM EVAPORATION OR
PRECIPITATES
LIMESTONE – CHEMICAL DEPOSITION OF
CALCITE
ROCK SALT – EVAPORATIVE DEPOSITION
OF HALITE
ROCK GYPSUM – EVAPORATIVE DEPOSITION
OF GYPSUM
LIMESTONE
ROCK GYPSUM
ROCK SALT
3. ORGANIC – SEDIMENTS FORMED FROM THE
REMAINS OF PLANTS AND ANIMALS
COQUINA – LIMESTONE FORMED BY THE
CALCUIM REMAINS OF MARINE ANIMALS
SHELL LIMESTONE – SHELLS CEMENTED BY
LIME OR CLAY MATRIX
BITUMINOUS COAL – COMPACTION OF
PLANT MATERIAL
COQUINA
SHELL LIMESTONE
BITUMINOUS
COAL
SEDIMENTARY ROCK FEATURES:
STRATIFICATION – THE DEPOSITION OF
SEDIMENTS INTO IN BEDS GIVES A LAYERED
APPEARANCE
BEDDING PLANE – THE LINE THAT SEPARATES
ROCK LAYERS. ORIGINALLY DEPOSITED IN
NEARLY HORIZONTAL POSITION.
CROSS BEDDING – BEDS ARE DEPOSITED IN
INCLINED LAYERS. COMMON IN WIND OR DELTAIC
DEPOSITS.
FOSSILS – THE REMAINS OR IMPRESSIONS OF
PLANTS OR ANIMALS IN ROCK
RIPPLE MARKS – FEATURES FORMED BY THE
ACTION OF WIND OR WATER CURRENTS.
MUD CRACKS – DEVELOP WHEN DEPOSITS WITH
HIGH % OF CLAY DRY AND CONTRACT.
CONCRETION – ROUND OR EGG SHAPED BODIES
FOUND IN LIMESTONE OR SHALEBEDS.