limestones

Question 1

dolomite is dominant in:

limestone is dominant in:

Answer 1

precambrian and paleozoic;

mesozoic and cenozoic

Question 2

three main groups of carbonate minerals:

Answer 2

calcite, dolomite, aragonite

Question 3

a rock composed of whole dolomite is called

Answer 3

dolostone

Question 4

ion substitution occur with atoms of:

Answer 4

similar charges and atomic radii

Question 5

staining in limestones:

Answer 5

calcite + Alizarin red + diluted HCl = red

aragonite + feigl’s solution = black

dolomite/Mg-calcite + titan yellow = yellow

Question 6

non-carbonate components of limestones

Answer 6

silicates, evaporite salts and sulfates, metal oxides

Question 7

explain how presence of metal oxides indicate reduction conditions

Answer 7

low sulfidation, high pH, thereby CacO3 precipitate

Question 8

what is the difference between calcite and aragonite?

Answer 8

calcite: stable
aragonite: metastable (unstable at surface)

Question 9

considered as double carbonates:

Answer 9

dolomite

Question 10

less stable polymorph of calcite

Answer 10

aragonite

Question 11

this refers to carbonate aggregates that make up the bulk of many limestones

Answer 11

allochems

Question 12

sizes of peloids, ooids, oncoids, and pisoids

Answer 12

0.02-0.05
0.1-2 (0.5 to 1 on average)
2-10
>10

Question 13

this allochem is determined to be fecal matter produced by marine organisms and is derived from pellets

Answer 13

peloids

Question 14

may occur as encrustations of cyanobacteria and algae

Answer 14

peloids

Question 15

concentric accretionary layers originated from a cortex or a nucleus of various composition and is wrapped around by carbonates

Answer 15

ooids

Question 16

radial ooids: quiet waters
______ ooids: dynamic water

Answer 16

concentric

Question 17

grains of cyanobacteria, red algae, bryozoans and bacterial origin

Answer 17

oncoids

Question 18

encrusted by micrite and may include some sand or silt particles

Answer 18

oncoids

Question 19

t or f: oncoids are invisible in the naked eye

Answer 19

F (visible)

Question 20

cave pearls (>10mm)

Answer 20

pisoids

Question 21

t or f: cave pearls are mostly non-marine

Answer 21

t

Question 22

sediments from the disturbed seafloor may enter carbonated rocks

Answer 22

intraclasts

Question 23

intraclasts may enter through:

Answer 23

bioturbation and erosional processes

Question 24

originated from weathering of older carbonate rocks

Answer 24

extraclasts

Question 25

microcrystalline calcite

Answer 25

micrite

Question 26

microcystalline carbonates

Answer 26

lime mud

Question 27

what constitutes marl?

Answer 27

lime mud with silicate sand and silt particles

Question 28

lime mud mixed with silicate sand and silt particles

Answer 28

marl

Question 29

t or f: sparrite occur larger than micrite

Answer 29

t

Question 30

size of sparite

Answer 30

0.02-1mm

Question 31

sparry calcite occur as cements in the form of:

Answer 31

best friends must stay together

bladed
fibrous
mosaic
syntaxial

Question 32

t or f: syntaxial cements are authigenic

Answer 32

t

Question 33

folk’s classification

Question 34

dunham classification

Question 35

this type of diagenesis removes aragonite and/or transforms to calcite

Answer 35

meteoric diagenesis

Question 36

differentiate meteoric and burial diagenesis of limestones

Answer 36

burial diagenesis reduces pore spaces and removes calcite and aragonite while meteoric diagenesis results in increase in porosity (dissolution) and removal/transform of aragonite

Question 37

modern ooids:
ancient ooids:

Answer 37

aragonite;
calcite