Physical Geology 101
13. Sedimentary Rocks I
(p. 194-208)
Sediment Deposition
Weathering results in rock being broken down into smaller fragments, called regolith. This regolith is then
broken down to form soil. The regolith may also be eroded and transported away from where it first
formed by the surface processes of water, wind, and ice.
Eventually, eroded material must get dropped somewhere else- a process called __________________.
The loose material that is deposited is referred to as _________________ which eventually bonds
together and hardens to form sedimentary rock.
How much of the Earth's crust is comprised of sedimentary rocks? _________
Nonetheless, sedimentary rocks cover most of the sea floor and about __________ of the continents, so
they are the type of rock that we see most often at the surface.
Sedimentary rocks are usually banded into many layers, one on top of the next, like a layered cake.
Example: __________________________.
We call these layers __________ or _____________, and the overall appearance is called either:
____________________
or
____________________.
Each bed is separated from the next by a break called a ________________________.
We can we distinguish one bed from another because they commonly show:
______________________________________________________
Significance of Sediments
The appearance of beds in sedimentary rocks and the type of sediment that makes up the rock can tell us
many things about the history of the Earth. This is because sediments tell us something about the surface
processes that created the sediment.
We can understand this by looking at the types of sediments we find in different environments on Earth
today.
Example: How different are the sediments found in river channels, lake bottoms, and beaches?
Fill in the type of sediment in each environment:
RIVER CHANNELS: ________________ LAKES: _______________ BEACHES: ________________
So different environments and on Earth, and the processes that occur there, tend to be associated with
different types of sediment.
What do we call these different types of environments? __________________________________.
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Physical Geology 101
Sedimentary rocks can tell us about the past distributions of rivers, lakes, oceans, deserts, and glaciers.
We may even learn about how climate changed over time in certain places.
Examples:
(1) In the Great Lakes region, we see evidence of long-term climate change in the sediments that
were: __________________________________________________
(2) In what type of ancient environment did the limestones in Florida form?
________________________________________________________________
Types of Sediment
Sediment comes in all different shapes and sizes, as well as being formed through different processes in
different depositional environments. We can divide sediment into three categories based on where it
came from:

_________________ sediment: broken down particles of rock produced by weathering and erosion.
Also called __________________ sediment.

_________________ sediment: precipitates out of water during evaporation or because of chemical
reactions in water.

_________________ sediment: mostly broken fragments of once living organisms, e.g. decayed
plants; seashells.
Detrital (Clastic) Sedimentary Rocks
Also called clastic sedimentary rocks. Detrital sediment may be transported and deposited by rivers,
lakes, glaciers, wind, waves, etc. (any surface process).
The individual grains in detrital sedimentary rocks are called __________________
which are made up of bits of individual minerals and sometimes fragments of broken down rocks that we
call __________________________.
Fill in the following chart showing the different types of clast grain sizes, and examples of materials
having a similar size:
CLAST NAME
SIZE
SIMILAR SIZE STUFF
OTHER INFO
< 1/256 mm
aka "mud"
1/256 - 1/16 mm
aka "mud"
1/16-2 mm
usually quartz
> 2mm
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Physical Geology 101
The names of the detrital sedimentary rocks that form from the different types of clastic sediment are
determined by the size of the clasts that make up the rock:
SEDIMENT SIZE
clay ->
ROCK NAMES
_________________ or _________________
Contains thin layers of sediment called ________________ or _________________
We can tell the difference between these two rocks through these characteristics:
Shale: if broken, it _____________________ (i.e., the rock is ____________)
Mudstone: this rock is more _______________.
SEDIMENT SIZE
silt
->
ROCK NAME
________________________
What are simple tests for the presence of clay or silt in a rock?
Clay: ___________________________________________________
Silt: ____________________________________________________
SEDIMENT SIZE
sand ->
ROCK NAMES
_________________ or ________________ or _______________
How do these three rock types with sand-sized grains differ from each other?
Sandstone: the clasts are mostly made of _______________
Arkose: some of the clasts must be made of _______________
Graywacke: some of the clasts must be ______________________
SEDIMENT SIZE
pebbles +
->
ROCK NAMES
_________________ or _________________
We can tell these two apart because the clasts in conglomerate are ___________ whereas the clasts
in breccia are ______________.
Sorting and Rounding
Some sedimentary rocks are made up of a range of sizes of clasts. The range of clast sizes is a
characteristic called the sorting of the sediment.
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Physical Geology 101
If there are a range of sizes, the sediment is ____________________ but if the clasts are all about the
same size, the sediment is ____________________.
We can also characterize the clasts on the basis of their shapes, which we call the rounding of the
sediment.
The rounding can range from ___________________ to ____________________.
Rounding of sedimentary particles results from clasts being bashed together during transport. Small
particles of the clasts chip off, causing grains to become more and more rounded over time.
Examples:
beach sand is:
[well sorted
or
Also, ________________ sand is:
poorly sorted]
[well sorted]
[well rounded
or angular]?
[well rounded]
This type of sand will eventually form a type of rock called ______________________.
Sediment deposited by glaciers is called _____________ and is dumped in a big heap. The type of rock
that forms from it is called _________________.
glacial sediment is: [well sorted
or
poorly sorted]
[well rounded
or angular]?
Chemical Sedimentary Rocks
Chemical sediment forms when sediment particles form directly out of water through the process of
______________________. This can occur in one of two ways:
______________________ (e.g., dripstone and __________________)
or
______________________ (i.e., involving living things)
The most common inorganic mechanism by which chemical sediments form is by:

__________________: as water evaporates, minerals like ____________ or ___________ or
_______________ precipitate out of the water. e.g. Great Salt Lake; Dead Sea.
The type of rocks that results from evaporation are called ___________________.
e.g., evaporation of the _____________________ Sea in the Pliocene.
When organic processes result in the precipitation of chemical sediments, we say the rocks are:

__________________: plants and animals in water can alter the water chemistry. Organisms can
change the amount of dissolved CO2, which may cause __________ (i.e., ________________) to
precipitate out.
This is how many _________________ are formed.
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Physical Geology 101
What other mineral can precipitate out of water due to the presence of organic life, and what type of
rocks get formed by it?
MINERAL
ROCK
_______________________
_______________________
Biogenic Sedimentary Rocks
Biogenic sediment is the broken down remnants of once living organisms and so is not the same as
chemically produced biochemical sediment. The individual fragments of bones and teeth make a type of
sediment particle called ________________ sediment.
What two types of biogenic rocks contains lots of broken down fragments of coral, sea shells and the
CaCO3 skeletons of marine organisms?
_____________________ and ______________________
A type of limestone containing large seashell fragments is called _________________.
Some organisms have siliceous shells, meaning they are made of silica. These may accumulate on the
ocean floor to form a rock called ____________, which is usually so fine-grained, you can't see the
individual particles of quartz. (e.g., flint).
Rocks that are made up of the remains of plants are called ___________. The dead material accumulates
in thick piles, first forming ____________, which finally turns into coal because of high temperatures and
pressures underground.
Lithification
Loose particles of sediment that have not yet turned to rock are called:
____________________________
The phenomenon by which this sediment is turned into rock is called ______________. It literally means
"turn to stone". We say the sediment “lithifies.”
The chemical, physical, and biological processes that occur in the rock during lithification are called
diagenetic processes.
So the sediment is said to undergo _____________________ as it lithifies.
The three diagenetic processes are: ________________________________________.
 Compaction is when sediments get buried deeper and deeper because of all the material being piled
up on top. The sediments get compressed and any water present in the sediments starts to get
squeezed out like squeezing a wet sponge.

Cementation is when the water getting squeezed out of the sediments fills up gaps between the
sediment grain, called pore spaces, and minerals precipitate out of the water. These minerals start
gluing the grains together, so they are called cement.
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Physical Geology 101

Recrystallization is when some minerals change into stronger types of minerals due to increasing
pressure and temperature. The stronger minerals help bind the rock together.
FINAL QUESTION:
What minerals often form the cement that glues sediment particles together during diagenesis?
____________________ and __________________
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