Sedimentary Rocks and Processes

Question 1

What is sediment?

Answer 1

Particles transported by water, ice, wind, and gravity.

Question 2

What is stratification/bedding?

Answer 2

The arrangement of sedimentary particles in layers

Question 3

What is a stratum?

Answer 3

A distinct layer of sediment

Question 4

What do you call the top and bottom surfaces of a bed?

Answer 4

The bedding plane

Question 5

What are the 2 main types of sediment/

Answer 5

Clastic (‘rock’) and non-clastic

Question 6

What are the 2 main types of non-clastic sediment?

Answer 6

• Chemical precipitates
• Biogenic sediment (made from plants or animals)

Question 7

What are the 4 sub-categories of clastic sediment in size order?

Answer 7

Gravel
Sand
Silt
Clay

Question 8

How is sediment sorting described?

Answer 8

Poorly sorted (large range) or well sorted (similarly sized particles)

Question 9

What is till?

Answer 9

Glacial sediment

Question 10

How does water speed differentiate sediment?

Answer 10

Faster flowing water can transport larger/heavier particles
- As water slows, heavier particles are deposited first and lighter ones carried further

Question 11

What is roundness?

Answer 11

A measure of the sharpness of the edges of a particle

Question 12

What is sphericity?

Answer 12

A measure of how similar a particle’s shape is to that of a sphere

Question 13

Used together, what can sorting, roundness and sphericity tell us?

Answer 13

About the environment sediment was transported and deposited in

Question 14

What is graded bedding? What does it show?

Answer 14

A bedding in which particles are deposited mostly by size with the coarsest at the bottom
- Shows a change in energy of the depositional system over time

Question 15

What is cross bedding? What does it show?

Answer 15

Inclined beds of sediment.
- Shows dominant wind directions

Question 16

What is diagenesis?

Answer 16

Sediment becoming rock ( a collective term for all processes including compaction and chemical processes )

Question 17

What is lithification?

Answer 17

The overall process for creating sedimentary rock

Question 18

What is the difference between lithification and diagenesis?

Answer 18

Lithification is the overall process of creating sedimentary rock.
Diagenesis is the collective term for all chemical, physical, and biological processes that cause lithification.

Question 19

What is compaction as a diagenesis process?

Answer 19

The weight of an accumulating sediment forces the grains together and the pore space is reduced.

Question 20

What is cementation?

Answer 20

Substances dissolved in water precipitate to form a cement that binds sediment grains together

Question 21

How do cementation and compaction work together?

Answer 21

Water being squeezed out by compaction allows chemicals to precipitate and cement.

Question 22

What is recrystallisation?

Answer 22

Less stable minerals recrystalise into more stable forms

Question 23

What is dissolution?

Answer 23

When some minerals are dissolved during burial

Question 24

Name 4 common clastic sedimentary rocks.

Answer 24

Conglomerate, Breccia, Sandstone, Mudstone/Shale

Question 25

What are the 4 vague categories of sedimentary structures?

Answer 25

• erosional
• depositional
• biogenic
• post depositional

Question 26

What type of rock is coal?

Answer 26

A biogenic sedimentary rock

Question 27

How is coal formed/

Answer 27

Plant remains accumulate and form peat which is compressed to become coal

Question 28

How are erosional structures formed?

Answer 28

Aqueous flows run over recently deposited sediment and gouge out depressions which are usually then infilled by sediment from the flow

Question 29

What are the two most notable erosional structures?

Answer 29

Flute marks (asymmetric dips, wider upstream), Groove marks (ridges)

Question 30

What do depositional structures depend on?

Answer 30

Flow velocity, flow depth, grain size

Question 31

What are some examples of depositional structures?

Answer 31

Ripples, dunes, cross stratification

Question 32

What are biogenic structures?

Answer 32

Structures left by animals such as burrows

Question 33

Name two types of biogenic structures.

Answer 33

Ichnofacies, Bioturbation

Question 34

What is an ichnofacie?

Answer 34

Trace fossil left by something like a burrow or feeding structure

Question 35

What are bioturbations?

Answer 35

Shapes/erosions in sediment caused by things like footprints

Question 36

Name two post-depositional structures?

Answer 36

Mud cracks, raindrop depressions

Question 37

What is an evaporite?

Answer 37

A rock formed from salts produced by evaporation

Question 38

What makes biogenic sediment bioclastic sediment?

Answer 38

When the remains of plants/animals are then broken and scattered

Question 39

What is deep sea ooze?

Answer 39

Fine deep sea mud formed of skeletal material

Question 40

What are the two types of deep sea ooze?

Answer 40

Calcareous ooze is made from material with more than 30% calcium carbonate
Siliceous ooze is made from material that’s mostly silica

Question 41

What are stromatolites? How are they formed?

Answer 41

Algae reef systems, formed incrementally as algae deposit calcium in laminations

Question 42

What are BIFs?

Answer 42

Banded iron formations, iron concentrations in layers

Question 43

What is limestone?

Answer 43

Rocks formed from the deposition of calcium carbonate

Question 44

What is oolitic limestone?

Answer 44

Limestone containing 0.5-2mm spherical grains of carbonate, shaped when these particles roll around in tidal environments

Question 45

What is chalk formed from?

Answer 45

Compacted carbonate shells of coccolithophores