Lesson 5: Sedimentary Rocks Flashcards by Ashley De Guzman

It needs to exist for sedimentary rocks to form

Sediments

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For sediments to exist rocks have to be

weathered, eroded, transported, deposited

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means being exposed to weather

Weathering

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Weathering will result to

sedimentary clasts (or solid fragments),
ions in solutions (which can form minerals later on), and soil.

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sedimentary clasts also known as

solid fragments

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The process of cracking due to loss of pressure is called

EXFOLIATION

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Water gets into cracks, and if it turns into ice, it worsens the crack

FROST WEDGING

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The freezing water expands in the soil and pushes the overlying material upward. This becomes a problem for roads as it may damage them.

FROST HEAVING

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Salt water infiltrates rocks, as the water dries, the salt crystals grow in the rock and crack it.

SALT CRYSTAL FORMATION

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Plants can weather rocks when

their roots grow through rocks

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• Removal of weathered materials
• Helps weathering happen more as weathered materials are moved
and thus exposing the rock again.

EROSION

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Erosion has several agents these are

Gravity
Wind
Water
Waves
Animals

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Greatly dependent on the environmental conditions (normally, greatest at warm and wet climates) and minerals present.

Chemical Weathering

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2 types of chemical weathering

MINERALS INTO OTHER MINERALS (ex. Feldspar becomes
clay minerals through hydrolysis)
• MINERALS GETTING DISSOLVED INTO A SOLUTION (ex.
Calcite can be dissolved by acidic solutions)

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is very important in chemical

weathering

Carbonic Acid

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In the air, only very weak carbonic acid can be made but having more ____ in the soil can make water passing through it considerably more acidic.

CO2

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It plays important role in chemical weathering. An example is ferromagnesian silicates (Olivine, Pyroxene, etc) can be altered so that its iron becomes dissolved iron and undergo oxidation to create iron oxides

Oxidation

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sediment/dissolved ions movement from
point A (point where it was eroded) to point B (point where it
will be deposited)

Transportation

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sediments stops moving

Deposition

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Newer sediments bury the older sediments at point B

causing covering and compacting of material

Burial

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As they are buried, the sediments are

squeezed/compacted together.

Compaction

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at depths of hundreds to thousands of

meters, sediments cement together to form sedimentary rocks

CEMENTATION

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made up of sediments that were transported as

solid fragments or clasts

Clastic

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made up of sediments that were transported as

ions in solutions

CHEMICAL

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Rock/Mineral fragment of various sizes.

Clast

smallest sized clay is clay at around what size?

>0.0039 mm

________ of the medium (water or wind, mostly) is the key factor affecting which sediments it can move.

Velocity

what affects the velocity of a medium

Season, Geometry of path including meanders, slopes,

• _____ sediments may remain on the bed of a river and pushed along the way while ____- ones may be suspended in the water

Bigger, smaller

It is the term for a collection of processes that end up | turning SEDIMENT DEPOSITS INTO ROCKS.

Lithification

is where minerals crystallize in the pores and | contact points of the clasts causing them to become a whole unit.

Cementation

has at least 75% silt or clay composition and form in | very low-energy environment (lakes, deep parts of the ocean)

Mudrock

* If it is mostly clay, then the mudrock is called (a) * If it has beddings/lamination, then the mudrock is called (b) * Otherwise, it is just called (c)

(a) CLAYSTONE (b) SHALE (c) MUDSTONE

often classified as ORGANIC sedimentary rock due to its composition of decayed material, however, it can be thought of as under clastic rocks since it is made up of fragments of organic matter and it is always found along with other clastic rock layers (as a layer in between other clastic rocks)

Coal

Made up mostly of sand (other part is silt and clay)

Sandstone

* If silt and clay is <15% : | * If silt and clay is >15% :

“CLEAN SANDSTONE” or “ARENITE” | “WACKE”

the sandstone's sand-sized particle components are mostly made of

Quartz, | Feldspar, and Rock Fragments

Sedimentary rocks with significant amount of clasts bigger than 2mm will be known as

either conglomerate or breccia

the clasts are rounded (formed in high energy environments like swift rivers, hence the more rounded shape)

Conglomerate

the clasts are angular (formed in environments | where clasts not transported significantly, hence little effect on shape)

BRECCIA

Typically made up mostly of components transported as ions in a solution

CHEMICAL SEDIMENTARY ROCKS

It comes from the organisms like corals, urchins,

Carbonate sediments

rock that forms from | carbonate sediments

Limestone

Some organisms like radiolarians and diatoms use silica to make their shell. When they die, the shells settle down and become

chert

this rock dissolved iron in seawater becomes oxidized and insoluble and sinks until it becomes a rock.

BANDED IRON FORMATION

In dry areas, when waters in lakes and rivers evaporate, they become concentrated with dissolved salts which then crystallize. Some examples are carbonates, gypsum, halite, borax, etc

Evaporites

Sediments (ex. glacial till, gravel, sand, silt, clay) are moved by gravity and moving water and ice and is usually deposited in land areas or other water bodies like streams or rivers.

GLACIAL

Sediments (mainly angular fragments) are pulled | downwards by gravity and ends up in steep sided valleys.

ALLUVIAL

Sediments (gravel, sand, silt, sometimes organic matter) | are carried by water to streams and may be deposited there.

FLUVIAL

Sediments (sand mainly on edges, silt, clay, organic | matter) are moved by water flowing into a lake.

LACUSTRINE

Much like lacustrine but lakes are situated in arid | areas and sediments are mostly salts and clays

EVAPORITIC

Sediments are sand and silt carried by wind into deserts and coastal areas.

AEOLIAN

Sediments (Silt and clay) are moved by currents/tides to tidal flats.

TIDAL

Sediments (sand, silt, clay, organic materials) are moved by water into deltas.

DELTAIC

Sediments (gravel and sand) are carried by waves and | longshore currents into the beaches and sand bar

BEACH

Sediments (typically carbonates) are almost not | moved and settles to the lagoon bottom.

LAGOONAL

Carbonates are carried by waves and tidal currents to be deposited in reefs and basins around it.

REEF

Sediments (carbonates, sand, silt, clay) | are carried by waves and tidal currents to shelves and slopes shown in the figure (and sometimes lagoons)

SHALLOW WATER MARINE

Sediments (clays, carbonate mud, silica | mud) are washed by ocean currents into deep ocean abyssal plains shown in the figure.

DEEP WATER MARINE

Sediments (gravel, mud, sand) are carried by | underwater gravity flows into the slopes (before abyssal plains) and abyssal plains in the figure.

SUBMARINE FAN

sediments are deposited and accumulate horizontally. Any layers that are tilted must have been subject to tectonic forces.

PRINCIPLE OF ORIGINAL HORIZONTALITY

layers are deposited in sequence and older is always at the bottom (unless turned over by tectonic process)

PRINCIPLE OF SUPERPOSITION

any rock/fragment in a layer is older than the layer itself much like the rocks in a conglomerate is older than the conglomerate itself.

PRINCIPLE OF INCLUSIONS

fossils may be used to determine the age of the rock it is in.

PRINCIPLE OF FAUNAL SUCCESSION

``` layering of sediments that can be seen in changes in texture, color, composition, etc. It indicates changes related to the deposition of materials that may be due to seasonal, climates, or tectonic changes among others. ```

Bedding

are narrow gaps in between layers shown in a bedding. These may indicate periods with no deposition.

Partings

Bedding that has angled layers within horizontal beds. This forms due the sediments being deposited by water or wind.

Cross bedding

linked to cross bedding are ripples on the surface of the | sediment bed.

RIPPLES

``` Sediments in a flowing water body may become ________- – that is they tile towards one direction, with their tops tilting towards the direction of a flow ```

IMBRICATED

A bed where gradation/gradual change of grain size from large to small is seen as from bottom to top (known as normal graded beds). Some have large grains at the top and finer grains at the bottom known as reverse/inverse graded bed

Graded Bedding

when a shallow body of water dries up, the mud at its bottom dries up and cracks due to the clay in the mud shrinking as it dries.

MUDCRACKS