Sedimentary Rocks

Question 1

What is a sediment

Answer 1

A collection of loose earth material (rocks, minerals, soil, fossils)

Question 2

What are the different ways sediment can form? (4)

Answer 2

1. When an older larger rock breaks into smaller pieces
2. When a rock reacts with air or water and forms new minerals
3. When a mineral dissolves in water and reprecipitates somewhere else
4. When minerals dissolve in water and an animal extracts the ions to produce a shell

Question 3

What is weathering

Answer 3

Describes the processes used to create sediments

Question 4

What are the different types of weathering (2) and describe both

Answer 4

1. Physical weather, breaking large rocks into smaller rocks
2. chemical weathering, altering rocks or minerals with air or water producing new minerals and dissolved elements and compounds

Question 5

Two commons types of sediment and what is there texture

Answer 5

1. Clastic and has a clastic texture
2. Chemical and has a crystalline texture

Question 6

What is biogenic sediment and what type of sediment is it

Answer 6

sediment produced through biological activity and is a chemical sediment

Question 7

What are the types of clastic sediments (2) and what does each mean

Answer 7

1. Siliclastic, meaning it doesn’t come from dead things
2. Bioclastic, meaning it comes from dead things

Question 8

What is weathering and erosion, how do they differ

Answer 8

Weathering is how sediment is formed and erosion is how the sediment is picked up and transported

Question 9

What are the agents for erosion (4)

Answer 9

1. Air
2. Gravity
3. Ice
4. Water

Question 10

Clastic sediments are deposited when there is a drop in ______ of the medium in which it is traveling

Answer 10

Velocity

Question 11

What are the main depositional environments (3)

Answer 11

1. Continental
2. Coastal
3. Marine

Question 12

What is the Hjulström diagram and what does it describe

Answer 12

It predicts at a specific velocity what size grains can be transported or entrained

Question 13

What is the difference between entrainment and transportation

Answer 13

In entrainment, the sediment is fully suspended in the water and doesn’t touch the bottom. Whereas, in transportation the sediment is being pulled along with the current but is being dragged/bouncing along the bottom

Question 14

In the Hjulström diagram it shows that clay is harder to entrain than grains that are much larger, why is that?

Answer 14

Because some clay is platy and the inter-particle forces hold the plates together (van der Waals and electrostatic forces)

Question 15

What are the continental dispositional environments (6)

Answer 15

1. Lake
2. Desert
3. Wetland
4. Alluvian fan
5. River
6. Glacier

Question 16

What are the coastal dispositional environments (5)

Answer 16

1. Beach
2. Delta
3. Carbonate platform
4. Barrier island
5. Tidal wetland

Question 17

What are the marine dispositional environments (2)

Answer 17

1. Continental shelf
2. Abyssal plain

Question 18

What is a primary sedimentary structure and what are they (6) briefly explain each

Answer 18

Primary sedimentary structures are structures in a rock that was created at deposition
1. Stratas (roughly horizontal layers of sediment that have accumulated over time
2. Bed grading (a bed of sediment that is sorted by grain size, there are two types normal and reverse grading)
3. Cross-bedding (a bed that doesn’t run horizontally caused by ripples and dunes)
4. Ripples (ripples in the sediment caused by water running over the sediments, there are two types symmetrical and asymmetrical)
5. Imbricated pebbles (form when flat pebbles overlap because flowing water in rivers pushes over them causing them to point downstream)
6. Sole marks (grooves and indents that form either as an object is dragged across by a current, or caused by back-currents

Question 19

What is a secondary sedimentary structure and what are they (3) brief explain each

Answer 19

A secondary sedimentary structure is a structure that forms after deposition
1. Mudcracks (when the water dries up causing the clay to contract)
2. Bioturbation (a result of animals burrowing into the ground)
3. Soft sediment deformation (occurs when sediment is loaded onto waterlogged sediments and compression may cause the water to squeeze out deforming the horizontal bedding)

Question 20

What is lithification

Answer 20

Describes processes of turning sediment to stone

Question 21

What are the types of lithification (2)

Answer 21

1. Burial (due to burial)
2. Cementation (precipitation of chemical sediments between clasts)

Question 22

What are sedimentary rock types based on (2)

Answer 22

1. Texture (clastic or crystalline)
2. Composition (type of sediments its made of)

Question 23

What are the types of sedimentary rocks)

Answer 23

1. Siliciclastic rocks
2. Chemical sedimentary rocks
3. Bioclastic rocks

Question 24

What are siliciclastic sedimentary rocks are distinguished by (2)

Answer 24

1. Grain size and shape
2. In sandstone, also identify grain type (relative proportion of quartz, feldspar, lithics and clay)

Question 25

What are the types of siliciclastic sedimentary rocks from largest to smallest grain size (4)

Answer 25

1. Breccia or conglomerate
2. Sandstone
3. Siltstone
4. Shale or mudstone

Question 26

Chemical sedimentary rocks are distinguished by (1)

Answer 26

Crystal type

Question 27

What are the types of chemical sedimentary rocks (3)

Answer 27

1. Travertine (non-biogenic carbonate)
2. Rock salt
3. Chert (microcrystalline quartz)

Question 28

Bioclastic sedimentary rocks are distinguished by (2)

Answer 28

1. Grain size and shape
2. Grain type (chemical sediments like shells, or organic sediments like plants)

Question 29

What are the types of bioclastic sedimentary rocks (4)

Answer 29

1. Coquina (macroscopic shells)
2. Chalk (microscopic shells)
3. Chert (microcrystalline quartz)
4. Coal (Plants)