sedimentary rocks

Question 1

sedimentary rocks

Answer 1

form from sediments (mineral grains) deposited in water or air

Question 2

clastic sediments

Answer 2

form through breaking down pre-existing rock

Question 3

chemical sediments

Answer 3

form from directly precipitating from solution

Question 4

biochemical sediments

Answer 4

minerals precipitated by mediation of organisms from solution

Question 5

formation

clastic (detrital) sedimentary rock

Answer 5

weathering, erosion (transport), depostion, lithification

Question 6

types of weathering

physical weathering

Answer 6

jointing, frost wedging, root wedging (biological weathering), exfoliation (thermal expansion)

Question 7

types of weathering

chemical weathering

Answer 7

results primarily from the ability of water to dissolve rocks and minerals

H₂O + CO₂ = H₂CO₃ (carbonic acid) can dissolve minerals

Question 8

features of clastic sedimentary rocks

grain size

Answer 8

gets smaller as time passes and with transportation away from source region of sediments

Question 9

features of clastic sedimentary rocks

immature sediment

Answer 9

coarse, angular, very poorly sorted

Question 10

features of clastic sedimentary rocks

mature sediments

Answer 10

fine-grained, rounded, very well sorted (grain size becomes more uniform)

Question 11

features of clastic sedimentary rocks

classification by size

Answer 11

• > 2mm: breccia (angular), conglomerate (rounded)
• 0.0625-2mm: sandstone
• < 0.0625mm: siltstone, shale, mudstone

Question 12

chemical (inorganic) sedimentary rocks

Answer 12

an evaporite is deposit containing minerals that precipitated from an aqueous solution as a result of mineral saturation through evaporation

Question 13

chemical sedimentary rocks

example

Answer 13

banded iron formations: related to excess iron ions becoming oxidized during the Great Oxygenation Event; usually banded with iron-rich and silica-rich (chert) layers

Question 14

biochemical sedimentary rocks

example

Answer 14

• limestone - calcite/aragonite
• chalk - consists of shells of billions of microscopic calcareous organisms, coccoliths
• chert - aka flint, small particles of silica from shells of microscopic Radiolarian, microscopic quartz

Question 15

sedimentary structures

bedding plane

Answer 15

made up of layers (bed/strata), shows pause in deposition and change of conditions

Question 16

sedimentary structures

graded bedding

Answer 16

grain size variation within bed, coarse sediments at bottom, fine sediments at top, indicates change in the energy of deposition, used as a way up indicator

Question 17

sedimentary structures

cross-bedding

Answer 17

layers existing at high angles to other layers, truncation: cutting of one set of layers by younger ones

Question 18

sedimentary structures

bioturbation

Answer 18

burrows and trackways by organisms, can destroy structure and affect texture of sediments

Question 19

trace fossils

Answer 19

a record of activity of organisms in the depositional environment

Question 20

form from sediments (mineral grains) deposited in water or air

Answer 20

sedimentary rocks

Question 21

form through breaking down pre-existing rock

Answer 21

clastic sediments

Question 22

form from directly precipitating from solution

Answer 22

chemical sediments

Question 23

minerals precipitated by mediation of organisms from solution

Answer 23

biochemical sediments

Question 24

weathering, erosion (transport), depostion, lithification

Answer 24

formation

clastic (detrital) sedimentary rock

Question 25

jointing, frost wedging, root wedging (biological weathering), exfoliation (thermal expansion)

Answer 25

types of weathering

physical weathering

Question 26

results primarily from the ability of water to dissolve rocks and minerals

H₂O + CO₂ = H₂CO₃ (carbonic acid) can dissolve minerals

Answer 26

types of weathering

chemical weathering

Question 27

gets smaller as time passes and with transportation away from source region of sediments

Answer 27

features of clastic sedimentary rocks

grain size

Question 28

coarse, angular, very poorly sorted

Answer 28

features of clastic sedimentary rocks

immature sediment

Question 29

fine-grained, rounded, very well sorted (grain size becomes more uniform)

Answer 29

features of clastic sedimentary rocks

mature sediments

Question 30

• > 2mm: breccia (angular), conglomerate (rounded)
• 0.0625-2mm: sandstone
• < 0.0625mm: siltstone, shale, mudstone

Answer 30

features of clastic sedimentary rocks

classification by size

Question 31

an evaporite is deposit containing minerals that precipitated from an aqueous solution as a result of mineral saturation through evaporation

Answer 31

chemical (inorganic) sedimentary rocks

Question 32

banded iron formations: related to excess iron ions becoming oxidized during the Great Oxygenation Event; usually banded with iron-rich and silica-rich (chert) layers

Answer 32

chemical sedimentary rocks

example

Question 33

• limestone - calcite/aragonite
• chalk - consists of shells of billions of microscopic calcareous organisms, coccoliths
• chert - aka flint, small particles of silica from shells of microscopic Radiolarian, microscopic quartz

Answer 33

biochemical sedimentary rocks

example

Question 34

made up of layers (bed/strata), shows pause in deposition and change of conditions

Answer 34

sedimentary structures

bedding plane

Question 35

grain size variation within bed, coarse sediments at bottom, fine sediments at top, indicates change in the energy of deposition, used as a way up indicator

Answer 35

sedimentary structures

graded bedding

Question 36

layers existing at high angles to other layers, truncation: cutting of one set of layers by younger ones

Answer 36

sedimentary structures

cross-bedding

Question 37

burrows and trackways by organisms, can destroy structure and affect texture of sediments

Answer 37

sedimentary structures

bioturbation

Question 38

a record of activity of organisms in the depositional environment

Answer 38

trace fossils