Unit 1 Flashcards
1
Q
sedimentary petrology
A
study of sedimentary rocks (field, megascopic, and microscopic settings)
2
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sedimentary petrography
A
description and classification of sedimentary rocks, especially through microscopic examination
3
Q
sedimentary petrogenisis
A
origin and formation of sedimentary rocks
4
Q
field scale
A
outcrop
5
Q
megascopic scale
A
handspecimen
6
Q
microscopic scale
A
thin section
7
Q
percentage of earth’s surface covered by sedimentary rocks
A
66%
8
Q
average thickness of sedimentary rocks
A
1800m
9
Q
fluid
A
anything that takes the shape of its container; common geological fluids include ice, water, wind, and viscous fluids
10
Q
sediments
A
solid material that is moved and deposited in a new location
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
12
Q
types of sediments
A
lithogenous, biogenous, hydrogenous, and cosmogenous
13
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lithogenous
A
derived from weathering of rocks or lithics
14
Q
biogenous
A
derived from organisms
15
Q
hydrogenous
A
precipitated directly from water (eg halite)
16
Q
cosmogenous
A
extra-terrestrial sediment formed from meteoric debris
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)
18
Q
debrite
A
deposit formed by a sediment gravity flow
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
20
Q
geochronology
A
earth time; a defined division of absolute time; units in absolute time (early, middle, late)
21
Q
chronostratigraphy
A
rock time; the body of rocks deposited during a specific time interval (lower, middle, upper)
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
23
Q
Tertiary-Quaternary boundary
A
2.6 Ma
24
Q
Mesozoic-Cenozoic (KT or KP) boundary
A
65 Ma
25
Paleozoic-Mesozoic boundary
251 Ma
26
Precambrian-Cambrian boundary
542 Ma
27
Archaean-Proterozoic boundary
2.5 Ga
28
age of earth
4.6 Ga
29
lithostratigraphic units
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
30
biostratigraphy
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
31
basic lithostratigraphic units
supergroup, group, formation, and bed
32
diabase
a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro
33
Why aren’t igneous and metamorphic rocks stable at earth’s surface?
most rocks and minerals are stable at the conditions under which they form (lower temp, lower pressure, more O₂, CO₂, H₂O, and organic matter)
34
percentage of sedimentary rocks that are mudrocks
65%
35
percentage of sedimentary rocks that are sandstones
20-25%
36
percentage of sedimentary rocks that are carbonates
10-15%
37
three final end products of ideal weathering model
quartz sand, clay, and ions in solution
38
unloading
removal of overlying materials; the underlying rocks, released from overlying pressure, can then expand
39
frost action
an umbrella term used to describe mechanical weathering processes that break down rock from freezing and thawing action
40
root wedging
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
41
temperature change
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
42
Exfoliation/sheeting
unloading or stress-release weathering; caused by a change in pressure conditions as erosion removes overburden and rocks breaks into sheets
43
chemical weathering
changing the chemical composition of rocks and minerals
44
hydration
a form of chemical weathering in which the chemical bonds of the mineral are changed as it interacts with water
45
hydrolysis
a form of chemical weathering in which rocks are broken down by acidic water to produce clay and soluble salts
46
factors that affect weathering
water pervasivity, water dissociation, CO2 concentration, and temperature
47
paleosol
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
48
lithification
transforming sediment into rock or porosity destruction through compaction and cementation; three processes are involved
49
compaction
consolidation of sediments due to the intense pressing weight of overlying deposits; first step of lithification
50
cementation
the process by which dissolved minerals crystallize and glue sediment grains together; second step in lithification
51
recrystallization
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
52
soil and regolith
transitions between the atmosphere and lithosphere; the beginning stages in the generation of sedimentary rocks
53
catchment
an area that collects and drains rainwater; also known as a drainage basin or sediment source area
54
endorheic basin
basins that do not flow into an ocean or a sea
55
exorheic basin
basins that ultimately flow into an ocean or a sea
56
accommodation space
the space made available in a sedimentary basin for potential sediment accumulation
57
factors that affect accommodation space
sea-level rise (mostly glacio-eustatic), subsidence (mostly tectonic, can be related to sediment loading or fluid withdrawal)
58
sedimentary basins
the subsiding areas where sediments accumulate to form stratigraphic successions; tectonic setting is the premier criterion to distinguish different types of sedimentary basins
59
extensional basin
basin that occurs within or between plates and are associated with increased heat flow due to hot mantle plumes
60
collisional basin
basin that occurs where plates collide, either characterized by subduction of an oceanic plate or continental collision
61
transtensional basin
basin that occurs where plates move in a strike-slip fashion relative to each other
62
composition
dominant mineral makeup of a rock
63
texture
refers to particle shape, size, and fabric
64
fabric
orientation and packing of grains (rounded vs angular, degree of sorting, linear vs non-linear, grain-size, etc)
65
Udden-Wentworth grain size scale
Wentworth developed the size classes whereas Udden developed the logarithmic portion of the classifications; phi=-log2(d)
66
provenance
sediment source area
67
sorting
the distribution of grain size of sediments, either in unconsolidated deposits or in sedimentary rocks; indication of energy involved and duration of transport
68
poorly sorted
indicates that the sediment sizes are mixed
69
well sorted
indicates that the sediment sizes are similar
70
rounding
used to describe the shape of the corners of a particular grain; indicates the distance and time involved in sediment transport
71
sphericity
the degree to which a grain shape approaches a sphere
72
grain orientation
particular arrangement or stacking of grains; indicates current direction
73
sediment maturity
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
compositional maturity
sediment that has reached the ultimate mineral end member, quartz sand
75
textural maturity
sediment that is composed of perfect spheres and well sorted
76
texture
the size, shapes, and relationships between grains
77
common relationships between grains
crystalline and clastic
78
crystalline
crystals or recrystallized grains; can include chemical and biochemical rocks and cements
79
clastic
rounded to angular grains or fragments that are cemented together
80
diagenesis
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
epiclastic rudite
sedimentary rock whose fragments are derived from weathering and erosion (at or near the surface)
82
conglomerate
contains >30% clasts and is clast or matrix supported
83
diamictite
contains <30% clasts and is mud supported (no fissility)
84
extraformational
clasts derived from older rocks than the formation in which they are found
85
intraformational
clasts derived from the same formation in which they are found; occur in evaporite solutions, karst solutions, paleosols, intertidal deposits
86
flat-pebble/edgewise conglomerate
conglomerate (usually carbonate or mud rich) formed by the penecontemporaneous breakup and reworking of semi-consolidated, usually laminated, sediment; almost always intraformational
87
orthoconglomerate
generally clast supported, generally <15% matrix, generally water-laid, often stratified
88
paraconglomerate (diamictite)
generally matrix supported, >15% matrix, generally more matrix than clasts, typically deposited by viscous fluid, unstratified
89
olistostrome
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
oligomict (monomict) conglomerate
conglomerate containing clasts of one or two compositions (often quartz or chert)
91
polymict conglomerate
conglomerate containing rounded clasts of several different compositions
92
petromict conglomerate
conglomerate containing unstable or metastable clasts
93
fanglomerate
conglomerate deposited in an alluvial-fan environment; interpretive term
94
breccia
rudite containing >30% angular clasts; same classification terms (ortho-, para-, etc) used for conglomerates are used for breccias
95
wacke
sandstone with excessive (15-75%) matrix
96
graywacke
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
turbidite
a fine-grained sediment (or sedimentary rock) that gradually changes from coarse- to fine-grained and that was deposited by turbidity currents
98
turbidity current deposits
deposits from a form of underwater avalanche that is responsible for distributing vast amounts of clastic sediment into the deep ocean
99
greensand
sand or sandstone which has a greenish color due to quantities of glauconies and clay minerals; formed in shallow marine areas
100
glauconite
an iron potassium phyllosilicate mineral of a characteristic green color
101
common cements
quartz, calcite, and hematite
102
common matrices
micrite, clay, and sericite (fine micas)
103
wave base
the maximum depth at which a water wave's passage causes significant water motion, roughly 10m below surface
104
phytoplankton
plankton consisting of microscopic plants
105
zooplankton
plankton consisting of microscopic animals
106
benthic
the lowest level of a body of water ie the ocean floor
107
epifauna
animals living on the surface of the seabed or a riverbed
108
infauna
the animals living in sediments of the ocean floor or river or lake beds
109
shale constitutes
very tiny mud-size rock fragments, very fine planktonic organic matter, and clay-organic complexes
110
calcareous shale
shale with abundant CaCO₃ and poorly developed laminae; does not frac well
111
siliceous shale
hale with abundant SiO₂ and well-developed laminae; fracs well
112
Two common ways to preserve organic matter
rapid burial in a subsiding basin and generation of anoxia in a deep basin
113
oil shale
organic rich, fine grained, sedimentary rock containing significant amounts of kerogen from which shale oil can be produced
114
shale gas
natural gas produced from shales
115
fracking
injecting liquid at high pressure into underground rocks, boreholes , etc. so as to force open existing fissures and extract oil or gas
116
conventional reservoir
any reservoir in which fluids flow easily through the rock matrix
117
unconventional reservoir
any reservoir that requires post-drilling stimulation (eg fracking) to initiate economic production (ie shale)
118
difference between conventional and unconventional reservoirs
permeability
119
common mudrock depositional environments
alluvial environments, glaciers, non-glacial lakes, deltas, coastlines, and various marine environments
120
polymorphic
a compound with more than one mineral form
121
autochthonous (in situ)
rock deposited in place where it is found (most carbonate rocks)
122
allochthonous
rock deposited in different place than its found (most clastic rocks)
123
what precipitates most of the CaCO3 in limestone?
green algae
124
sole
bottom of a bed
125
sole marks
casts of hollows and marks left by currents on the bottom of beds; troughs filled with overlying unit, useful geopetal structure
126
groove casts
long, straight sole marks
127
bounce marks
sole marks from materials bouncing along the bottom of beds
128
flute casts
v-shaped sole marks, indicate current direction
129
geopetal structure
a sedimentary fabric which records the way up at the time of deposition; "way up" structure
130
flocule ripples
come from mud deposition in a high energy environment; teeny tiny crossbeds
131
floccule
a flake which is produced by the agglomeration of suspended solids (ie clay plates and organic material)
132
saltation
sand grains hop, skipping, and jumping along the bottom of a current flow
133
bedload
sediment transported along the bottom via traction transport
134
suspended load
sediment transported above the river bottom
135
dissolved load
dissolved ions transported by water current
