Section 7- Sedimentary Rocks

Question 1

Sedimentary Rock Formation

Answer 1

Deposition and lithification

Question 2

Deposition

Answer 2

laying down of material by a natural agent (air, water, ice, gravity)
or precipitation from solution

Question 3

lithification

Answer 3

Compaction
-process which pressure reduces the volume of sediment due to a reduction in void space
+
Cementation
-process by which clastic sediment are converted to rock by precipitation of mineral cement (calcite,quartz,iron oxides) between grains
-crystallizing in pore space to hold sediments together, happens when water flows through pores between sediments, ions in the water combine to form crystals to fill the pores and hold sediment together

Question 4

Sedimentary Rock Types

Answer 4

clastic (detrital)
- starts as clasts(fragments or particles)
-form from fragments of other rocks that have been weather, eroded, etc and overtime compacted and cemented together

Chemical (evaporites)
-formed by precipitation from solution

Organic (biogenetic)
-formed from previously living organisms

Question 5

Clastic (detrital)sedimentary rocks

Answer 5

composed of fragments of weathered and eroded rocks that are compacted and cemented together

Question 6

3 main types of clastic rocks

Answer 6

mudrock
-smaller particles, silt and clay
sandstone
-dominated by sand
conglomerate
-pebbles to boulders, rounded clasts
breccia
-pebbles to bouders, angular clasts

Question 7

chemical (evaporites) for sedimentary rocks

Answer 7

precipitation of minerals from solution
-often requires restricted basin in warm climate
-halite and NaCl

Question 8

organic (biogenic) sedimentary rocks

Answer 8

remains of living things
-limestone
-coal

Question 9

sedimentary structures:
bedding and ripples

Answer 9

Bedding
-layer of sedimentary rock with a recognizable top and bottom
-boundary between two is called bedding plane

Ripples
-symmetrical ripples formed by waves (both directions)
-asymmetrical ripples formed by wind or river (current in one direction) (gentle ->steep slope indicate current direction)

Question 10

Facies

Answer 10

a distinctive rock unit that forms under certain conditions of sedimentation, relfecting a particular process or environment

Question 11

Walthers Law

Answer 11

a vertical sequence of facies reflects a lateral change in depositional environment

Question 12

Marine Transgression

Answer 12

sea level rises
depositional environments migrate towards land
marine sediments (shale and limestone) deposited on top of continental sediments (sandstones)
(Coarse to fine sediment)

Question 13

Marine Regression

Answer 13

sea level falls
depositional environments migrate toward sea
continental desiment(Sandstone) deposited on top of marine sediments (shales nad limestones)
(Fine sediment to coarse)

Question 14

Angular unconformity

Answer 14

Younger sediment rets upon the eroded surface of tilted or folded older rocks

Question 15

Angular unconformity

Answer 15

Younger sediment rets upon the eroded surface of tilted or folded older rocks

Question 16

Disconformity

Answer 16

Contact between younger and older beds is marked by visible, irregular or euneven erosional surface

Question 17

Paraconformity

Answer 17

Beds above and below the unconformity are parallel and no erosional surface is evident; but can be recognized based on the gap in the rock record

Question 18

Nonconformity

Answer 18

Develops between sedimentary rock and older igneous or metamorphic rock that has been exposed to erosion