WEATHERING AND SEDIMENTARY PROCESSES

Question 1

• Sediment and sedimentary rock

Answer 1

5% of continent by volume, but 90% by surface area

Question 2

o Weathering-

Answer 2

 Sedimentary rocks are formed by weathering and erosion of other rocks

Question 3

o Physical weathering: physically weakening a rock and reduce the size

Answer 3

 Produces clastic fragments
 Transportation/ erosion
* Water, wind, ice, gravity
 Deposition
* Sedimentary environment
 Compaction and cementation
* Reduces pore space; cement (quartz, calcite, hematite) binds grains together (lithification) forms clastic rocks

Question 4

o Chemical weathering: change composition through processes such as oxidation and mineral composition (ions dissolved in water)

Answer 4

 Produces: ions in solution
 Transportation
* As dissolved ions and ionic groups in water
 Precipitation from solution
* Organic and inorganic form rocks called chemical precipitates

Question 5

o Clastic rocks

Answer 5

 Mostly from physical weathering
 Sandstone, mudstone

Question 6

o Chemical precipitates

Answer 6

 Mostly from chemical weathering
 Limestone, rock salt

Question 7

physical

Answer 7

mudrock, coal, sandstone, conglomerate, breccia

Question 8

 Mudrock

Answer 8

• Mudstone
  o >75% silt and clay, not bedded
• Shale
  o >75% silt and clay, thinly bedded

Question 9

coal

Answer 9

o Dominated by fragments of partially decayed plant matter often enclosed between beds of sandstone or mudrock

Question 10

 Sandstone

Answer 10

• Quartz, sandstone
  o Dominated by sand, >90% quartz
• Arkose
  o Dominated by sand, >10% feldspar
• Lithic, wacke
  o Dominated by sand, >10% rock fragments, >15% silt and clay

Question 11

 Conglomerate

Answer 11

o Dominated by rounded clasts, granule size and larger

Question 12

 Breccia

Answer 12

o Dominated by angled clasts, granule size and larger

Question 13

chemical

Answer 13

 Most common: limestone “carbonate CaCO3” rock , chert, BIR, evaporites

Question 14

 Limestone

Answer 14

• Continental shelves, tropical regions (coral reef)

Question 15

chert

Answer 15

• Microcrystalline silica- ocean floor

Question 16

banded iron formation

Answer 16

• Deep sea, iron dissolved in water is oxidized = insoluble and precipitating

Question 17

evaporites

Answer 17

• Arid regions of lakes with no ocean stream outlet
• Salts saturate and precipitate out of solution
  o Gypsum and halite commonly formed this way

Question 18

o Sedimentary rocks take millions to 10s of millions of years to become lithifies- need to be deposited into a basin, formed by tectonic process, that will last

Answer 18

 Trench, forearc, back arc basin, rift basin

Question 19

o The principles

Answer 19

 Principle of horizontality
 Principle of superposition
 Principles of inclusions; rock fragments are older
 Principle of faunal succession – age of species in the fossils

Question 20

o Clues to environments of deposition

Answer 20

 Grain composition
* Conglomerate, breccia (angular)
 Grain size, sorting, and shape
* Amount of energy to move
 Sedimentary structures
 Fossils

Question 21

o Bedding

Answer 21

 Arrangement into layers by composition, weathering, texture

Question 22

o Cross bedding

Answer 22

 Current (water/ wind) change direction

Question 23

graded bedding

Answer 23

 Gradtional change in grain size within a single layer (finer as you go up)
 Turbidite
* Deposited by turbidity (underwater avalanche) dumping mass volumes of sediment into deep ocean

Question 24

o Mud cracks

Answer 24

 Arid environments with seasonal precipitation or very shallow water

Question 25

o Ripple marks

Answer 25

 Indicated currents or waves – sand dunes

Question 26

• Fossils and economic resources in sedimentary rocks

Answer 26

o Fossils
 Marine – shells, shark teeth, microfossils
 Non-marine (terrestrial)- flowering plants, ferns, animals, dinosaurs
o Resources
 Oil and gas, Coal, Gypsum, Rock salt, Fertilizer, Uranium