SEDS: Sandstone

Question 1

the abundance of a particular mineral in a sedimentary rock is dependent on

Answer 1

availability, mechanical and chemical stability

Question 2

quartz will likely be the only grain that will survive in this condition.

Answer 2

low relief and humid climate

Question 3

unstable grains will survive in this area

Answer 3

high relief

Question 4

Unstable grains are called

Answer 4

Labile grains

Question 5

formed by the breakdown of pre-existing rocks by weathering and erosion, and from material that forms within the depositional environment.

Answer 5

Sand grains

Question 6

2 types of breakdown products

Answer 6

detrital mineral grains, lithic fragments

Question 7

Grains that form within the depositional environment are principally ___________

Answer 7

biogenic in origin

Question 8

defined as a sedimentary rock with grains of these sizes.

Answer 8

Sandstone

Question 9

Minerals that grow as crystals are called

Answer 9

Authigenic materials

Question 10

Major Components of Sandstone

Answer 10

Detrital Minerals
Lithic Fragments
Biogenic particles
Authigenic materials – (Minerals that grow as crystals)
Matrix – Fine-grained material

Question 11

types of lithic grains can be related to the plate tectonic setting of the provenance terrane and adjoining sedimentary basin

Answer 11

Rock Fragments

Question 12

very useful in studies of the provenance of sandstone, but intravaginal lithics, which are commonly of mud and carbonate, are usually excluded.

Answer 12

Rock Fragments

Question 13

________ rocks tend to break into individual grains

Answer 13

Plutonic rocks

Question 14

most common mineral in sandstone; most stable of all minerals

Answer 14

Quartz

Question 15

The average sandstone contains about ____ quartz

Answer 15

65%

Question 16

Quartz in Sandstone is derived from

Answer 16

granitoid rocks, acid gneisses and schists

Question 17

Why is K feldspare (ortoclase and microcline) are much more common in sand stone than plagioclase?

Answer 17

because K feldspar is chemically more stable and is more common in continental basement rocks.

Question 18

Plagioclases are more common in sandstones derived from

Answer 18

uplifted oceanic and island-arc terranes

Question 19

feldsp content is largely controlled by

Answer 19

rate of erosion and climate

Question 20

Humid climates

Answer 20

promotes destruction of feldspars

Question 21

in Arid environment

Answer 21

-fresh feldsp survive

Question 22

___________ will produce some feldsp. grains in spite of a humid climate

Answer 22

Rapid erosion

Question 23

The average percentage of feldspar in Sandstones

Answer 23

10-15%

Question 24

The average percentage of feldspar in Arkoses

Answer 24

(commonly) reach up to 50%

Question 25

common in the matrix of sandstones and coarse clastic.

Answer 25

Phyllosilicates

Question 26

derived from many igneous rocks but are especially from metamorphic rocks.

Answer 26

Muscovite (more common) and biotite

Question 27

both detrital and authigenic. Kaolinite, illite, chlorite, smectites, and mixed-layer clays.

Answer 27

Clay

Question 28

reflect source geology, climate, and weathering processes

Answer 28

Detrital clays

Question 29

Study of ___________ gives indications of provenance and of events in the source area

Answer 29

Heavy Minerals

Question 30

Metamorphic terranes

Answer 30

garnet,, epidote, and staurolite

Question 31

Major changes in the source-area geology, such as the uplift and unroofing of a granite may be recorded in

Answer 31

Heavy min assemblage

Question 32

iron potassium phyllosilicate (mica group

Answer 32

Glauconite

Question 33

the Fe2+ end member of the chlorite group; A hydrous aluminum silicate of iron, which is produced in an environment of low to moderate grade of metamorphosed iron deposits, as gray or black crystals in oolitic iron ore.

Answer 33

Chamosite

Question 34

a method whereby a thin section on a petrographic microscope is examined by stepping across the thin section at equal intervals and identifying the material (quartz, feldspars, rock fragments, or matrix) that lies immediately beneath the crosshairs.

Answer 34

Point counting

Question 35

Counting ________ grains will accurately yield the proportion of each component.

Answer 35

250 to 300

Question 36

graph used for the classification of Sandstone

Answer 36

Petti-john

Question 37

Sandstones with at least 95% quartz grains

Answer 37

Quartz Aranite

Question 38

the most compositionally mature, usually consisting of well-rounded and well-sorted grains so that textural maturity is also very high.

Answer 38

Quartz Arenite

Question 39

in many cases, these are the products of extended periods of sediment reworking

Answer 39

quartz arenites

Question 40

Why is climate a factor in the composition of Sandstones?

Answer 40

warm, humid climate will lead to the removal of many unstable grains.

Question 41

factors that allow quartz to dominate in sandstones.

Answer 41

humid climate, low relief, and slow sedimentation

Question 42

Many quartz grains in these arenites are

Answer 42

2nd cycle (derived from older sediments)

Question 43

Quartz arenites produced by persistent waves or current reworking were deposited on

Answer 43

stable cratons and passive margins

Question 44

sandstone that has >25% feldspar, much quartz, and some rock fragments

Answer 44

Arkose

Question 45

Arkoses are derived from _________________ and vary from in situ weathering products to sandstones that have undergone long transport.

Answer 45

granites and gneisses

Question 46

Arkoses are typically

Answer 46

poorly- to well-sorted, with very angular to subrounded grains

Question 47

conditions that are favorable for feldspar to form Arkose

Answer 47

semi-arid and glacial climates, very rapid erosion, and High relief (despite of intense chem weathering)

Question 48

Many arkoses were deposited in

Answer 48

fluvial environments

Question 49

Lithic > Felds; These rocks range widely in composition (both grain types and chemistry), depending largely on the rock fragments present.

Answer 49

Litharenites

Question 50

The immature composition of Litharenites implies

Answer 50

high rates of sediment production followed by short transport distances

Question 51

sandstone with a fine-grained matrix, which consists of an intergrowth of chlorite, sericite, and silt-sized grains of quartz and feldspar.

Answer 51

Graywackes

Question 52

Origin of the matrix = “greywacke problem."

Answer 52

(a) fine-grained sediment deposited along with the sand fraction, and (b) diagenetic alteration of unstable rock fragments.

Question 53

Feldspar grains in Graywackes are chiefly

Answer 53

Na plag

Question 54

Greywackes are ___________ in color

Answer 54

dark gray or black