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GLE 2024 (Day 2) > SEDIMENTARY PETROLOGY (BIOGENIC, CHEMICAL, AND VOLCANICLASTICS) > Flashcards

SEDIMENTARY PETROLOGY (BIOGENIC, CHEMICAL, AND VOLCANICLASTICS) Flashcards

1
Q

Differenatiate Calcareous and Carbonaceous?

A

Calcareous are used to describe sediments which soliidy to form limestones which are rich in CaCO3 while Carbonacous are used fro materials rich in carbon such as coal

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2
Q

How would you differentiate quartz from calcite?

A

Calcite is soft with hardness of 3 and can be scratched easily by pen-knife while quartz is 7 and is harder than the metal blade.

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3
Q

How many % of mg to qualify for low and high-Mg Calcite?

A

Low: <4%,
High: 11-19%

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4
Q

Organisms that have high Mg Calcite?

A

Echinoderms, Barnacles, Foraminifers

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5
Q

Difference between calcite and aragonite?

A

Calcite is hexagonal while aragonite is orthorhombic. Aragonite is more densely packed and isthus denser with G=2.95. Calcite is 2.74-2.94. Aragonite is harder (3.5-4).

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6
Q

Inverterbrates which has aragonitic composition for hard parts

A

Bivalves and Corals

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7
Q

Chemical formula of dolomite?

A

CaMg (CO3)2

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8
Q

When you stain dolomite with Alizarin Red-S, what would be the contrast with other carbonates?

A

No change in color but for makes other carbonates pink

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9
Q

This dye is used to distinguish between ferroan and non-ferroan carbonates?

A

Potassium ferricyanide

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10
Q

What would be the color if iron in the carbonate reacts with potassium ferricyanide?

A

Blue

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11
Q

How can you make thin sections for carbonates?

A

Acetate peels

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12
Q

Organisms which usually appear as single crystals?

A

Crinoids, Echinoids and calcareous sponges

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13
Q

Homogenous crystals?

A

Trilobites, Ostracods, and molluscs

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14
Q

Lamellar form?

A

molluscs

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15
Q

primsatic form?

A

Molluscs

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16
Q

Foliated form?

A

brachiopods and other moluscs

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17
Q

granular form

A

Foraminifera and mollluscas

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18
Q

nacreous

A

molluscs

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19
Q

Radial form?

A

belemnites

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20
Q

Spherulitic?

A

Corals

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21
Q

modern calcitic bivalves

A

oysters and scallops

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22
Q

molluscs which have distinct coiled form and have calcitic or aragonitic layered structure

A

Gastropods

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23
Q

have layered shell structure, which includes modern nautilus and the coiled chambered ammonites

A

Cephalopods

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24
Q

A cephalopod that has cigar-shape guard of radial fibrous calcite which is common in Mesozoic Sed Rocks

A

Belemnites

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25
Q

shelly organisms with 2 shells similar to bivalves but are made up of low magnesium calcite nad a two-layer structure of fibrous crystals which may be preserved

A

Brachiopods

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26
Q

The exoskeletons of these organism as made up of prisms of calcite that are elongate perpendiular to the edges of the plates

A

Trilobites

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27
Q

Examples of Arthropods?

A

Triblobite and Barnacles

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28
Q

sea urchins?

A

Echinoids

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29
Q

Sea lilies?

A

Crinoids

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30
Q

small single celled marine organisms which range from few tens of microns in diameter to tens of mm

A

Foraminifera

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31
Q

Contrast planktonic and Benthic?

A

Planktonic means floating while benthic are those which live on the sea floor

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32
Q

Hard outer parts of forams made up possibly of high and low mg calcite

A

Tests

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33
Q

What is the class of corals?

A

Cnidaria

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34
Q

Whats the contrast between older and younger corals?

A

Older are made primarily of calcite while the
younger ones are aragonite-rich

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35
Q

Corals which have symbiotic relationship with algae that require clear, warm, shallow marine waters

A

Hermatypic Corals

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36
Q

Corals that do not have algae and can exist in cooler, deeper water?

A

Ahermatypic Corals

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37
Q

Singe-celled protozoans w/c are mainly encrusting organism made up of aragonite and/or high mg calcite

A

bryozoa

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38
Q

sedentary organisms that may form hard parts of calcite which some may also be of silica or protein composition

A

Sponges (Porifera)

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39
Q

Calcareous sponges that were common in Palaeozoic

A

Stromatoporoids

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40
Q

Annelid worms which secrete tubes of carbonates (Calcitic, or aragonitic) as they encrust pebbles or other hard parts of other organisms

A

Serpulid

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41
Q

A carbonate producing alage which isknown as corraline algae which have a layered structure and are effective at binding soft substrate

A

Red algae (Rhodophyta)

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42
Q

Algae that have calcified stems and branches and often sgmented which contribute fine grains and rods of Calcite when the organism dies

A

Green Algae (Chlorophyta)

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43
Q

these are spherical bodies of few tens of microns made of of plates which are important constituent of pelagic limestone such as cret chalk

A

Cocolithophores

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44
Q

These are flat or domes structures formed by trapping of finegrained carbonates by the filaments and stick surfaces of cyanbacteria. These are also considered as some of the earliest lifeforms on Earth

A

Stromatolites

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45
Q

Cyanobacterial communities which have an irregular form

A

Thrombolites

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46
Q

irregular concentric structures mm to cm accross formed of layers bound by cyanobacteria found as clasts w/in carbonate sediments

A

Oncoids

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47
Q

The action of cyanobacteria to alter original structure of a shell into fine-grained micrite

A

Micritisation

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48
Q

spherical bodies of CaCO3 less than 2mm in diamter which have an internal strucure of concentric layers which suggest precipitation of CaCO3 aroun the surface of the sphere

A

Ooids

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49
Q

what may be the nucleus of an ooid?

A

a carbonate materials or a clastic sand grain

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50
Q

A rock made up of carbonate ooids?

A

Oolitic Limestones

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51
Q

How does ooids form?

A

Chemical precipitation out of agitated water saturated in CaCO3 in calcium cabonate in warm waters

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52
Q

How can you differentiate Pisoids from ooids?

A

Pisoids have a dimater of over 2mm and are more irregular in shape but similar in form and origin to ooids

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53
Q

Round particles made up of fine-grained clacites found in sediments which do not show any concentric structures and didnt grow in water

A

Peloids or Faecal Pellets

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54
Q

What organisms usually produced these particles which are less than a mm across?

A

gastropods

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55
Q

fragments of CaCO3 material that has been partly lithifed, an then broken up an reworked to form a clast which is incorporated into the sediment

A

Intraclasts

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56
Q

rounded carbonate grains consisting of several fragments of CaCO3 cemented together

A

Grapestone

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57
Q

Fine -grained carbonate particles less than 4microns across which may be purely precipitated from CaCO3 saturated water, from breakdown of skeltal framents or algal or backerial origin

A

Lime Mud,Carbonate Mud or Micrite

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58
Q

the most widely used schme for limestone description in the field both in mesoscopic and microscopic scale which is based on texture, including the proportion of carbonate mud present and the overall framework of the rock

A

Dunhman Classficcation

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59
Q

A rock consisting entirely of ooids with no matrix?

A

OOlitic Grainstone

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60
Q

Rock with 75% shelly fragments in a matrix of carbonate mud

A

bioclastic packstone

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61
Q

In limestone petrographic analysis, a high proportion of fine-grained carbonate materials imply that?

A

rock was formed in a relatively low-energy setting

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62
Q

Absence of mud in a limestone imply that?

A

High energy environment of roc formation

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63
Q

What does high concentration of ooids indicate?

A

Shallow, wave-dominated coastl setting

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64
Q

What would be the depositional evnrionment of a rock composed of biogenic material of same group of organisms such as bivalves or gastropods?

A

Lagoonal Setting

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65
Q

What would be the indicator if shells are composed mainly of aragonite or high mg calcite?

A

When primary fabric is lost due to recrystallisation

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66
Q

organism which te to retain primary structures

A

LowMg Calcite such as brachiopods and Bivalves

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67
Q

Minerals formed by precipitation our of solutions as ions became more concentrated when water evaporates?

A

Evaporites

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68
Q

Ave dissolve ions in Sewater?

A

35 part per thousands

69
Q

Order of precipitation of evaporite minerals?

A

CaCO3, Calcium Sulphate, Sodium Chloride then Potassium and Magnesium Chlorides

70
Q

This will precipiate once evaporation concretae seawater to 19% of its original volume

A

Cacium Suplhate

71
Q

Differntiate Anhydrite and Gypsum?

A

Gypsum is hydrous

72
Q

Slender crystals of Gypsum?

A

Selenite

73
Q

forms as a results of rehydration of anyhdrite and has fine crystalline form in nodules

A

Alabaster

74
Q

How can you distinguidh Gypsum from Calcite and Halite

A

Gypsum is softer with hardness of 2 and can be scratched by fingernail and does not taste salty

75
Q

How can you differentiate gypsum and anhydrite?

A

Gypsum is less denser and softer while Anhyrite is harder and cannot be scracthed by fingernail (3.5), under the microscpore, Gypsum has low relief and has interference color of low-order grays while anhydrite has high relief and have moderate high-rder colours

76
Q

When will calcite precipitate from Sewater?

A

when evaporation concentrate seawater to <50% of its original volume

77
Q

Precipitates our of seater once it as been concentrated to 9.5% of its orignal volume

A

Halite (NaCl)

78
Q

Halite with stepped or stairlike crystal face?

A

Hoppe Crystal

79
Q

Contrast haltie and sylvite

A

Halite is Sodium chloride and has salty taste while sylvite is potassium chlorid with bitter taste

80
Q

Striking characteristics of halite under microscope?

A

It is isotropic, has stronge cleavage planes because it is isometric

81
Q

Lakes that have the same dissolved ions as sewater?

A

Saline Lakes

82
Q

Minerals which may precipitate from Saline lakes?

A

Trona Na2CO3, Mirabilite Na2SO4, and Epsomite (MgSO4)

83
Q

Silica which is made up of radating fibers a few tens to hundreds microns long?

A

Chalcedony

84
Q

Fine-grained siliceous sed rocks made up of microcrystalline quartz and chalcedony

A

Cherts

85
Q

These froms on the seafloor or lake floor by accumulation of siliecous skeletons of microscopic oranism which becomes chert

A

Siliecous Ooze

86
Q

siliecous microoganism in lakes or in freshwater?

A

Diatoms

87
Q

Common siliceous microoganism marine environments?

A

Radiolaria

88
Q

differentiate radiolaria and diatoms

A

Radiolaria are zooplankton while diatoms are phytoplankton

89
Q

Cyrptocrystalline silca with water in mienral strcuture

A

Opal

90
Q

Depositional evnironment of Cherts?

A

Deep-Marine

91
Q

How does diagenetic Cherts form?

A

when SiO2 replaces unstable materials in a rock by water rich in silica flowing through the rock

92
Q

Texture of Diagenetic Cherts

A

Nodular

93
Q

Dark Chert

A

Flint

94
Q

Hardest Sedimentary Rock

A

Cherts

95
Q

What gives jasper its strong red color?

A

Hemattite

96
Q

What does chert look like under the microscope?

A

Radiating fibers of chalcedony or completely interlocking microquartz grains

97
Q

What depositonal environemnt are phosphatic materials usally associated?

A

Shallow marine continental shelf deposits

98
Q

Calcium phospahtes which occur as accessory minerals in granitic rocks

A

Apatite

99
Q

Where does phosphates usually occur?

A

High organic Productivity envir and with low oxygen content

100
Q

Rocks with concenration of 5-35% P2O5

A

Phosporites

101
Q

calcium hydroxl fluorapatite?

A

Francolite

102
Q

Fossilated faeces of fishes or animals

A

Coprolite

103
Q

Sed rocks with at least 15% iron

A

Ironstones or iron formations

104
Q

from which age are most iron rock mined today came from?

A

Precambrian

105
Q

black mineral which occurs as accessory mineral in igneous rocks and as detrital in seds

A

Magnetite (Fe3O4)

106
Q

most common oxide mineral which is bright red to black and occurs as weathering or altertion product in seds and sed rocks?

A

Haematite (Fe2O3)

107
Q

Iron hydroxide that is widespread in sediments as yellow-brown mienrals which may be primary deposit or weathering product representing less oxidizing conditions than haematite

A

Goethite (FeO.OH)

108
Q

Why are young deserts yellowish in color?

A

Because of Geothite content

109
Q

Why are ancient deserts reddish in color?

A

Because Geothite already oxidized ,cause by post depositional processes, into haematite giving it a reddish color

110
Q

A hyrated iron oxide that is amorphous

A

Limonite

111
Q

Differentiate Goethite, Limonite, Magnetite and Hematite in Thin Section

A

Iron Oxides are opaque while magnetite is black and often euhedral while haematite occurs in variety of form which is red in reflected light. Geothite and Limonite are yellow-brown in thin sections and are anisotropic

112
Q

Common iron rich sulphide minerals found in ign and met rocks as brassy cubic crystals and occurs finely disseminated particles which may give dark coloration to sediments

A

Pyrite (FeS)

113
Q

Iron rich phyllosilicates minerals found in ironstones and formed either as authigenic and diagenetic

A

Greenalite (Serpentine)
and Chamosites (Chlorite)

114
Q

A phyllosilicate formed through authigenetic processes in shallow marine environments

A

Glauconite

115
Q

siderite rich mudstones are associated with what environment?

A

Freshwater reducing conditions such as
non-saline marshes

116
Q

A sed rocks consisting of alternating laminated or thin bedded alternations of heamatite rich seds and other material which is typically siltsone or chert (Silica Rich) which there is no equivalent forming today

A

Banded Iron Formations (BIFs)

117
Q

Age range of BIFs

A

2.5-1.9 Ga Precambrian

118
Q

an example of ferromanganese deposit form at any depth authigenically in a very slow manner and are only found concentrated deep in the oceans where the rate of deposition of other sed is even slower

A

Manganese Nodules

119
Q

Seds or sed rocks with high conc of organic matter

A

Carbonaceous

120
Q

whats the range for a mudrock to be considered as carbonaceous?

A

> 2%

121
Q

Whats the range for a limestone to be carbonaceous?

A

> 0.2%

122
Q

Whats the range of organic matter content for a sandstone to be carbonaceous?

A

> 0.05%

123
Q

Enviroment with very limited to no oxygen?

A

Anaerobic

124
Q

This may form from long term accumulation of dead vegatation favored by wet anaerobic conditions of mires, bogs, and swamps

A

Peat

125
Q

At present where does peat forms?

A

from Subarctic boggy regions to mangrove swamps in the tropics

126
Q

What is the ideal area for pure peat formation?

A

areas with little clastic input

127
Q

Remains of planktonic algae, spores and very fine detritus from larger plants that accumulates underwater in anaerobic conditions?

A

Sapropel

128
Q

Organisms whose remains will ultimatey form liquid and gaseous hydrocarbons?

A

Zoonplankton and Phytoplanktons and bacteria

129
Q

how much of a rock must be organic matter to qualify as coal?

A

2/3

130
Q

Non organic, non combustible material of Coals

A

Ash

131
Q

When will a coal be economic?

A

If ash content is less than 10%

132
Q

this is a heterogenous type of coal made up of different types of vegetation

A

Peat

133
Q

Coals that is bright, shiny black that usually breaks cubically and consisting of woody tissues

A

Vitrain

134
Q

Black or grey in color, dull and rough usually contains a lot of spore and detrital plant material

A

Durain

135
Q

Black fibrous with a silky luster, friable and soft coal that represent fossil charcoal

A

Fusain

136
Q

Banded, layered coal that consists of alternation of the other three types

A

Clarain

137
Q

A coal with chonchoidal fracture

A

Sapropelic

138
Q

Sapropelic Coal with dull black luster rich with spores

A

Cannel Coal

139
Q

Saproperlic Coal with black/brown color rich with algae

A

Boghead Coal

140
Q

Particle types making up the coal

A

Macerals

141
Q

How do you observe coal under thin section?

A

Polished surfaces under a thin layer of oil using reflected light

142
Q

Macerals in which the oirgin is mainly cell walls of woody tissues and leaves

A

Vitrinite

143
Q

Macerals which comes mainly from spores ,cuticles and resins

A

Liptinite

144
Q

Macerals which are burnt, oxidised, or degraded plant material

A

Inertinite

145
Q

A technique used to analyse coal by measuring the amount of light reflcted from the polished surface

A

Reflectance

146
Q

Differentiate Macerals in terms of reflectance?

A

Liptinite have low reflectance while inertinite have high reflectance and vitrinite reflectance varies on coal rank

147
Q

A technique used to determine the rank of coal and is a measure of the burial temperature of the bed and also provides a measure of the burial depth of a bed in basin analysis

A

Vitrinite reflectance

148
Q

relation of coal rank with T

A

As T in burial increases, Rank increases

149
Q

Mudrocks which contains high proportion of organic material that can produce liquid oil or gas

A

Oil Shales

150
Q

Organic material, usually of algae, which are broken down to form long chain of hydrocarbons

A

Kerogen

151
Q

Most important source rock

A

Shale

152
Q

Environment which favors source rock formations?

A

Lakes, restricted shallow marine environments

153
Q

Clastic sediments that are saturated with hydrocarbons and they are exposed equivalents of oil reservoirs

A

Tar sands/ Oil Sands

154
Q

What happens to organic matter in the formation of tar sands?

A

Biodegraded into bitumen

155
Q

Differentiate Basaltic and Silicic Magma in terms of Volcanoclastic content

A

Basaltic usually ejects large volumes of lava but small volcanic ash while silicic are those which have large amounts of molten rocks ejected

156
Q

Collective terms for pyroclastic materials?

A

Tephra

157
Q

Diferentiate pyroclastic and volcanoclastic?

A

Pyroclastic is mainly particles ejected by the volcano while volcaniclastic are those which are composed mainly of volcanic detritus

158
Q

Differentiate volcanic blocks and bombs

A

Both are coarse materials over 64mm in diameter but blocks are ejected in a solid form while bombs are those which were partially motlen and have cooled in the air

159
Q

Blocks that are consolidated into a rock?

A

VOlcanic Breccia

160
Q

Bombs consilidated into a rock

A

Agglomerate

161
Q

Pyroclastic materials with 2-64 mm diameter or granule to pebble size

A

Lapilli

162
Q

Consolidated lappili?

A

Lapillistone

163
Q

Speherical aggreggates of fine ash formed during air fall which is a bit moist

A

Accretionary Lapilli

164
Q

Unconsolidated sand, silt, and clay grade pryoclastic materials

A

Ash

165
Q

Lithified ash from volcanic eruptions

A

Tuff

166
Q

3 usual compositions of vocaniclastic rocks?

A

Mineral grains, Lithic fragments and Vitric materials (Glass Shards and Pumice)

167
Q

These are small dark lenses of glassy material usually of pumice that were softened and compressed in flame like structures during welding of tuff

A

fiamme

168
Q

A rock that have fiamme structures

A

Ignimbrite / Welded Tuff

GLE 2024 (Day 2) (41 decks)

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