Transcript Sedimentary Rocks

Sedimentary Rocks
Terms to know

Transportation – currents of wind and water and
the movement of glaciers, transport particles
downhill or downstream

Deposition – (also called sedimentation) –
sediment particles settle out as wind or water
currents slow, or as glacier edges melt
Terms to know
– As layers of sediment accumulate, older
deposited material is compacted and buried in the
crust
 Burial
– Physical and chemical changes,
including pressure, heat and chemical reactions.
Once this occurs, a new identity for the rock
results
 Diagenesis
Categories of Sedimentary Rock
 Clastic
 Chemical
 Organic
Sedimentary Rocks
•formed by the lithification of unconsolidated sediments.
•lithification is a process of compaction and cementation
The weight of overlying sediments causes sediments to
be reduced in volume by 40%
•
There is also an increase press and temp
• The heat causes some minerals to melt, like silica and
calcite
•
these go into solution and fill spaces between
remaining grains.
• They then harden to form a glue or cement:
cementation
Clastic

Rocks form from bits and
pieces of other rocks

Weathering and erosion by
rivers, ice, wind and
waves carry sediment
down to the sea
Major Classes of Clastic Sedimentary
Rocks
Conglomerate
Coarse grain particles
Boulder
larger than 256mm
About 10 inches
Cobble
256-64mm
about 2.5 inches
Pebble
64-2mm
about .08 inches
Major Classes of Clastic Sedimentary
Rocks
Sandstone
Medium particle size
Sand
2 - .062 mm
Major Classes of Clastic Sedimentary
Rocks
Siltstone
Fine grained particles
Silt
.062 - .0039 mm
Major Classes of Clastic Sedimentary
Rocks
Mudstone, Shale,
Claystone
Very fined Grained sediments
Clay
Finer than .0039 mm
Clastic – classifications

Sorting

Particles that are close to
the same size = well sorted


beach
Particles that are not the
same size = poorly sorted

River
Clastic – classifications

Shapes of Clastics

Angular – particles have
not traveled very far from
the parent rock

Rounded – rocks have
traveled far from parent
rock
Clastic - Conglomerate

Lithified equivalents of
gravel (looks like gravel
that is stuck together)
Found in river beds and
old drainage basins
 Roundness of clastics tell
the story of travel

Clastic - Sandstone
Lithified equivalent of
sand (looks like sand is
stuck together
 Cross-bedding – layers of
different colors

Tells the story of
paleocurrents
 Reveals the former stream,
wind, or shallow marine
water flows

Clastic - Siltstone

Lithified equivalent of silt
(looks like silt is stuck
together)

Look similar to mudstone
or very fine grained
sandstone
Clastic – Mudstone

Muds are deposited by
rivers and tides
After a river has flooded its
lowlands and the flood
recedes, the current slows
and the mud settles
 Deep ocean floor is covered
by muds, due to weak or
absent currents

Clastic - Shale

Shales are composed of
silt and clay

Have been known to
contain large quantities of
oily organic material (oil
shale)
Clastic - Claystone

Either wind blown or
water deposited

Particles are the finest of
all clastic sizes

Dust settles after a wind
storm
Chemically- Formed Sedimentary
Rocks

Chemically- Formed sedimentary rocks are derived from
minerals carried in solution into lakes and seas.
Limestone
 Dolomite
 Travertine
 Gypsum
 Rock Salt
 Chert

Chemical - Limestone

Fine to coarse grained
bedded rock

Contains calcite (calcium
carbonate)

Fizzes with acid
Chemical - Dolomite

Fine to coarse grained
bedded rock

Contains dolomite
(calcium, magnesium
carbonate)

Fizzes with acid
Chemical – Travertine

Found in caves – water passes
through cave walls, pulls
calcite out of rock and
peculates onto the floor

Contains calcite


Fizzes with Acid
Stalactites and Stalagmites
Chemical - Gypsum

It is formed by the
evaporative deposition of
gypsum from solution.

commercially very
important for the
production of plaster of
Paris and gypsum
wallboard for house
construction
Chemical – Rock Salt




This is the common name for
the mineral "halite".
table salt
It is typically formed by the
evaporation of salty water
(such as sea water)
dry lake beds, inland marginal
seas, and enclosed bays and
estuaries in arid regions
Chemical – Chert


Chert is composed
mostly of the mineral
chalcedony—silica, or
quartz in crystals of
submicroscopic size.
forms in the deep sea
where the tiny shells of
siliceous organisms are
concentrated, or where
underground fluids
replace sediments with
silica
Organic – Sedimentary Rock
 Organically-formed
sedimentary rocks form from
the remains of plants and animals
 Fossil
Limestone
 Coal
 Coquina
Organic – Fossil Limestone

Fine to coarse grained
bedded rock

Contains calcium
carbonate (fizzes w/acid)
Often contains identifiable
fossil shells
-found in marine
environments

Organic - Coal

Black to brown in color

Contains compacted beds
of peat and other organic
debris
Found in areas that at one
time were heavily wooded
Coquina

Mostly consists of shells
or fragments of shells

It is a limestone – so it
will fizz with acid

Found in marine
environments