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EES 450 > Unit 1 > Flashcards

Unit 1 Flashcards

1
Q

sedimentary petrology

A

study of sedimentary rocks (field, megascopic, and microscopic settings)

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2
Q

sedimentary petrography

A

description and classification of sedimentary rocks, especially through microscopic examination

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3
Q

sedimentary petrogenisis

A

origin and formation of sedimentary rocks

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4
Q

field scale

A

outcrop

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5
Q

megascopic scale

A

handspecimen

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6
Q

microscopic scale

A

thin section

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7
Q

percentage of earth’s surface covered by sedimentary rocks

A

66%

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8
Q

average thickness of sedimentary rocks

A

1800m

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9
Q

fluid

A

anything that takes the shape of its container; common geological fluids include ice, water, wind, and viscous fluids

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10
Q

sediments

A

solid material that is moved and deposited in a new location

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11
Q

sedimentary rocks

A

form from sediments that accumulate in fluids at or near the surface and consist of accumulations of chemical/biochemical precipitates and/or fragments or grains of rocks, minerals, and fossils

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12
Q

types of sediments

A

lithogenous, biogenous, hydrogenous, and cosmogenous

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13
Q

lithogenous

A

derived from weathering of rocks or lithics

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14
Q

biogenous

A

derived from organisms

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15
Q

hydrogenous

A

precipitated directly from water (eg halite)

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16
Q

cosmogenous

A

extra-terrestrial sediment formed from meteoric debris

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17
Q

diamictite

A

a poorly sorted or non-sorted terrigenous non-calcareous rock than contains various sized clasts; often formed due to viscous fluid movement (mud flows, glaciers, etc)

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18
Q

debrite

A

deposit formed by a sediment gravity flow

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19
Q

bentonite

A

an absorbent swelling clay that usually forms from the weathering of volcanic ash in seawater or by hydrothermal circulation through the porosity of volcanic ash beds

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20
Q

geochronology

A

earth time; a defined division of absolute time; units in absolute time (early, middle, late)

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21
Q

chronostratigraphy

A

rock time; the body of rocks deposited during a specific time interval (lower, middle, upper)

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22
Q

Glocal Boundary Stratotype Section and Point (GSSP)

A

reference points on stratigraphic sections of rock which define the lower boundaries of stages on the International Chronostratigraphic Chart; physically marked with golden spikes

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23
Q

Tertiary-Quaternary boundary

A

2.6 Ma

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24
Q

Mesozoic-Cenozoic (KT or KP) boundary

A

65 Ma

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25
Q

Paleozoic-Mesozoic boundary

A

251 Ma

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26
Q

Precambrian-Cambrian boundary

A

542 Ma

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27
Q

Archaean-Proterozoic boundary

A

2.5 Ga

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28
Q

age of earth

A

4.6 Ga

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29
Q

lithostratigraphic units

A

a defined body of sedimentary, extrusive igneous, metasedimentary, or metavolcanic strata that is distinguished and delimited on the basis of lithic characteristics and stratigraphic position; it generally conforms to the Law of Superposition and is commonly stratified and tabular in form

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30
Q

biostratigraphy

A

focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them; the main unit is a zone and biozone

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31
Q

basic lithostratigraphic units

A

supergroup, group, formation, and bed

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32
Q

diabase

A

a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro

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33
Q

Why aren’t igneous and metamorphic rocks stable at earth’s surface?

A

most rocks and minerals are stable at the conditions under which they form (lower temp, lower pressure, more O₂, CO₂, H₂O, and organic matter)

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34
Q

percentage of sedimentary rocks that are mudrocks

A

65%

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35
Q

percentage of sedimentary rocks that are sandstones

A

20-25%

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36
Q

percentage of sedimentary rocks that are carbonates

A

10-15%

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37
Q

three final end products of ideal weathering model

A

quartz sand, clay, and ions in solution

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38
Q

unloading

A

removal of overlying materials; the underlying rocks, released from overlying pressure, can then expand

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39
Q

frost action

A

an umbrella term used to describe mechanical weathering processes that break down rock from freezing and thawing action

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40
Q

root wedging

A

roots force their way into even the tiniest cracks and exert tremendous pressure on the rocks as they grow, widening the cracks and breaking the rock

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41
Q

temperature change

A

changes in temperature cause rock to expand (with heat) and contract (with cold); as this happens over and over again, the structure of the rock weakens

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42
Q

Exfoliation/sheeting

A

unloading or stress-release weathering; caused by a change in pressure conditions as erosion removes overburden and rocks breaks into sheets

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43
Q

chemical weathering

A

changing the chemical composition of rocks and minerals

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44
Q

hydration

A

a form of chemical weathering in which the chemical bonds of the mineral are changed as it interacts with water

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45
Q

hydrolysis

A

a form of chemical weathering in which rocks are broken down by acidic water to produce clay and soluble salts

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46
Q

factors that affect weathering

A

water pervasivity, water dissociation, CO2 concentration, and temperature

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47
Q

paleosol

A

ancient soils, formed on landscapes of the past; most paleosols have been buried in the sedimentary record, covered by flood debris, landslides, volcanic ash, or lava

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48
Q

lithification

A

transforming sediment into rock or porosity destruction through compaction and cementation; three processes are involved

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49
Q

compaction

A

consolidation of sediments due to the intense pressing weight of overlying deposits; first step of lithification

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50
Q

cementation

A

the process by which dissolved minerals crystallize and glue sediment grains together; second step in lithification

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51
Q

recrystallization

A

minerals will recrystallize as a response to a change in their chemical environment; can involve entire grain reformation or just minerals rims; important process in the formation of limestone

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52
Q

soil and regolith

A

transitions between the atmosphere and lithosphere; the beginning stages in the generation of sedimentary rocks

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53
Q

catchment

A

an area that collects and drains rainwater; also known as a drainage basin or sediment source area

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54
Q

endorheic basin

A

basins that do not flow into an ocean or a sea

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55
Q

exorheic basin

A

basins that ultimately flow into an ocean or a sea

56
Q

accommodation space

A

the space made available in a sedimentary basin for potential sediment accumulation

57
Q

factors that affect accommodation space

A

sea-level rise (mostly glacio-eustatic), subsidence (mostly tectonic, can be related to sediment loading or fluid withdrawal)

58
Q

sedimentary basins

A

the subsiding areas where sediments accumulate to form stratigraphic successions; tectonic setting is the premier criterion to distinguish different types of sedimentary basins

59
Q

extensional basin

A

basin that occurs within or between plates and are associated with increased heat flow due to hot mantle plumes

60
Q

collisional basin

A

basin that occurs where plates collide, either characterized by subduction of an oceanic plate or continental collision

61
Q

transtensional basin

A

basin that occurs where plates move in a strike-slip fashion relative to each other

62
Q

composition

A

dominant mineral makeup of a rock

63
Q

texture

A

refers to particle shape, size, and fabric

64
Q

fabric

A

orientation and packing of grains (rounded vs angular, degree of sorting, linear vs non-linear, grain-size, etc)

65
Q

Udden-Wentworth grain size scale

A

Wentworth developed the size classes whereas Udden developed the logarithmic portion of the classifications; phi=-log2(d)

66
Q

provenance

A

sediment source area

67
Q

sorting

A

the distribution of grain size of sediments, either in unconsolidated deposits or in sedimentary rocks; indication of energy involved and duration of transport

68
Q

poorly sorted

A

indicates that the sediment sizes are mixed

69
Q

well sorted

A

indicates that the sediment sizes are similar

70
Q

rounding

A

used to describe the shape of the corners of a particular grain; indicates the distance and time involved in sediment transport

71
Q

sphericity

A

the degree to which a grain shape approaches a sphere

72
Q

grain orientation

A

particular arrangement or stacking of grains; indicates current direction

73
Q

sediment maturity

A

a relative measure of how extensively and thoroughly a siliciclastic sediment has been weather, transported, and reworked towards its ultimate end product (quartz sand)

74
Q

compositional maturity

A

sediment that has reached the ultimate mineral end member, quartz sand

75
Q

textural maturity

A

sediment that is composed of perfect spheres and well sorted

76
Q

texture

A

the size, shapes, and relationships between grains

77
Q

common relationships between grains

A

crystalline and clastic

78
Q

crystalline

A

crystals or recrystallized grains; can include chemical and biochemical rocks and cements

79
Q

clastic

A

rounded to angular grains or fragments that are cemented together

80
Q

diagenesis

A

the set of processes that a sediment undergoes from the moment of its deposition until the moment it reaches the conditions of the metamorphic environment or until it is again exposed to weathering

81
Q

epiclastic rudite

A

sedimentary rock whose fragments are derived from weathering and erosion (at or near the surface)

82
Q

conglomerate

A

contains >30% clasts and is clast or matrix supported

83
Q

diamictite

A

contains <30% clasts and is mud supported (no fissility)

84
Q

extraformational

A

clasts derived from older rocks than the formation in which they are found

85
Q

intraformational

A

clasts derived from the same formation in which they are found; occur in evaporite solutions, karst solutions, paleosols, intertidal deposits

86
Q

flat-pebble/edgewise conglomerate

A

conglomerate (usually carbonate or mud rich) formed by the penecontemporaneous breakup and reworking of semi-consolidated, usually laminated, sediment; almost always intraformational

87
Q

orthoconglomerate

A

generally clast supported, generally <15% matrix, generally water-laid, often stratified

88
Q

paraconglomerate (diamictite)

A

generally matrix supported, >15% matrix, generally more matrix than clasts, typically deposited by viscous fluid, unstratified

89
Q

olistostrome

A

large scale diamictite deposit formed by debris flows and submarine landslides, commonly in continental-slope and trench environments; often occur at subduction zones in accretionary wedges

90
Q

oligomict (monomict) conglomerate

A

conglomerate containing clasts of one or two compositions (often quartz or chert)

91
Q

polymict conglomerate

A

conglomerate containing rounded clasts of several different compositions

92
Q

petromict conglomerate

A

conglomerate containing unstable or metastable clasts

93
Q

fanglomerate

A

conglomerate deposited in an alluvial-fan environment; interpretive term

94
Q

breccia

A

rudite containing >30% angular clasts; same classification terms (ortho-, para-, etc) used for conglomerates are used for breccias

95
Q

wacke

A

sandstone with excessive (15-75%) matrix

96
Q

graywacke

A

informal term for dark-gray, coarse-grained sandstones consisting of poorly sorted, angular to subangular grains of quartz, feldspar, dark minerals, and lithic fragments in a fine-grained, compact, clayey matrix; if possible, use should be avoided

97
Q

turbidite

A

a fine-grained sediment (or sedimentary rock) that gradually changes from coarse- to fine-grained and that was deposited by turbidity currents

98
Q

turbidity current deposits

A

deposits from a form of underwater avalanche that is responsible for distributing vast amounts of clastic sediment into the deep ocean

99
Q

greensand

A

sand or sandstone which has a greenish color due to quantities of glauconies and clay minerals; formed in shallow marine areas

100
Q

glauconite

A

an iron potassium phyllosilicate mineral of a characteristic green color

101
Q

common cements

A

quartz, calcite, and hematite

102
Q

common matrices

A

micrite, clay, and sericite (fine micas)

103
Q

wave base

A

the maximum depth at which a water wave’s passage causes significant water motion, roughly 10m below surface

104
Q

phytoplankton

A

plankton consisting of microscopic plants

105
Q

zooplankton

A

plankton consisting of microscopic animals

106
Q

benthic

A

the lowest level of a body of water ie the ocean floor

107
Q

epifauna

A

animals living on the surface of the seabed or a riverbed

108
Q

infauna

A

the animals living in sediments of the ocean floor or river or lake beds

109
Q

shale constitutes

A

very tiny mud-size rock fragments, very fine planktonic organic matter, and clay-organic complexes

110
Q

calcareous shale

A

shale with abundant CaCO₃ and poorly developed laminae; does not frac well

111
Q

siliceous shale

A

hale with abundant SiO₂ and well-developed laminae; fracs well

112
Q

Two common ways to preserve organic matter

A

rapid burial in a subsiding basin and generation of anoxia in a deep basin

113
Q

oil shale

A

organic rich, fine grained, sedimentary rock containing significant amounts of kerogen from which shale oil can be produced

114
Q

shale gas

A

natural gas produced from shales

115
Q

fracking

A

injecting liquid at high pressure into underground rocks, boreholes , etc. so as to force open existing fissures and extract oil or gas

116
Q

conventional reservoir

A

any reservoir in which fluids flow easily through the rock matrix

117
Q

unconventional reservoir

A

any reservoir that requires post-drilling stimulation (eg fracking) to initiate economic production (ie shale)

118
Q

difference between conventional and unconventional reservoirs

A

permeability

119
Q

common mudrock depositional environments

A

alluvial environments, glaciers, non-glacial lakes, deltas, coastlines, and various marine environments

120
Q

polymorphic

A

a compound with more than one mineral form

121
Q

autochthonous (in situ)

A

rock deposited in place where it is found (most carbonate rocks)

122
Q

allochthonous

A

rock deposited in different place than its found (most clastic rocks)

123
Q

what precipitates most of the CaCO3 in limestone?

A

green algae

124
Q

sole

A

bottom of a bed

125
Q

sole marks

A

casts of hollows and marks left by currents on the bottom of beds; troughs filled with overlying unit, useful geopetal structure

126
Q

groove casts

A

long, straight sole marks

127
Q

bounce marks

A

sole marks from materials bouncing along the bottom of beds

128
Q

flute casts

A

v-shaped sole marks, indicate current direction

129
Q

geopetal structure

A

a sedimentary fabric which records the way up at the time of deposition; “way up” structure

130
Q

flocule ripples

A

come from mud deposition in a high energy environment; teeny tiny crossbeds

131
Q

floccule

A

a flake which is produced by the agglomeration of suspended solids (ie clay plates and organic material)

132
Q

saltation

A

sand grains hop, skipping, and jumping along the bottom of a current flow

133
Q

bedload

A

sediment transported along the bottom via traction transport

134
Q

suspended load

A

sediment transported above the river bottom

135
Q

dissolved load

A

dissolved ions transported by water current

EES 450 (1 decks)

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