sedimentary Rocks

Question 1

sedimentary rocks are?

Answer 1

Compacted and cemented sediment from erosion and/or chemical deposition

Question 2

what is the importance of sedimentary rocks?

Answer 2

fossils, natural gas and oil. used to tell history of area

Question 3

how much does sedimentary rocks form on earth

Answer 3

cover 75-80% of land surface of earth, but <5% of earth’s crust

Question 4

how long does it take for sedimentary rocks to form

Answer 4

they can take 1000’s to millions of years to form

Question 5

lithification

Answer 5

loose sediments are transformed into solid rock by
compaction
cementation

Question 6

what is the most important feature

Answer 6

formation of layers (strata)

Question 7

fluvial and delta systems

Answer 7

-complex area where rivers enter the ocean
-sand, silt and mud predominate
-lead to formation of sandstones and conglomerate rocks
-associated with river transport

Question 8

alluvial fan and glacial systems

Answer 8

-found at the base of mountain ranges in arid regions
-thick gravel deposits often associated with debris flows
-most common rock formed is conglomerate
-transports unsorted mixed load of large boulders, gravel, sand and silt
-deposition occurs near margins of glaciers as they retreat
-deposits are called ‘glacial till’ and form glacial conglomerate

Question 9

eolian (dunes) and shorelines

Answer 9

-associated with wind-driven sand dunes
-well-sorted, can show cross-bedding
-major rock types is, of course, sandstone
-beaches
-when waves are present, mud is cleaned out and only sand remains- well-ssorted
-typical rock is sandstone

Question 10

other systems include

Answer 10

lagoons
shale
shales

Question 11

sedimentary rock classifications are

Answer 11

clastic/detrital
bioclastic/biochemical
organic
chemical

Question 12

clastic/detrital

Answer 12

sedimentary rocks- sandstone

Question 13

bioclastic/biochemical

Answer 13

sedimentary rocks- limestone

Question 14

organic

Answer 14

made from decayed plant material

Question 15

chemical

Answer 15

sedimentary rock- rock salt

Question 16

types of sandstone

Answer 16

quartz sandstone( most common)
arkose (25% feldspars)
Bituminous
graywacke

Question 17

sediment facies

Answer 17

-sequences of rock indicating a certain environment of formation
-marine transgression marine regression

Question 18

graded bedding= decrease in grain size upward though the layer

Answer 18

-produced on the ocean floor by turbidity currents
-turbidity currents are underwater landslides
-rocks with graded bedding are called “turbidites”

Question 19

surface impressions

Answer 19

-things like mudcracks, ripple marks, dinosaur tracks
-these can be preserved in stream deposits as well as ocean deposits
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