Sedimentary Rocks Flashcards

Terms Definitions
Several beds together
Coarse-GrainedRounded grainsForms from sedimetn deposited in a fast-moving riverTraveled a short distance from it's sourceModerately to poorly sorted
Water is Universal Solvent
Cross-beds develop in wind-blown sediment(ex: barchan sand dunes). Sand grains saltate (bounce) along the stoss-face and then avalanche down the steep, lee face, where wind velocities are reduced.
Very-fined grained sedimantary rock that breaks into sheets.
largest detrital sedimentary rock made of sharp pieces
Clastic Rocks
Pieces glued togetherClassified based on TEXTURETexture = size, shape, sorting of CLASTSFine-grained (shale, siltstone)Medium-grained (sandstone)Coarse-grained (conglomerate, breccia)(This is different from texture in igneous rocks which is determined by the size of CRYSTALS, not clasts)
Sedimentary rock made of sand-sized grains with quartz & feldspar
Turbidity Current
Moving submarine suspension of sediment.
Chemical Sediments
no mechanical breakdownform via reactions Rocks usually comprised of 1 major mineral type -acid rain, saltwater evaporation
Occurs when hydrogen ions replace positive ions in minerals
This alters the composition of the mineral by producing soluble substances and/or iron which can be oxidized
Source Rock
marine detrital sediments (like shale)
boulder gravel sand dust
examples of detrital rocks
Sedimentary Structure
Layering of sedimentary rocks, for surface features on layers formed during deposition, & for the arrangement of grains with layers.
chemical Sedimentary rock
Made of minerals from groundwater
unstable minerals can be altered into stable formsbreakdown of organic matter in presence of oxygen
a hydrocarbon in liquid or gaseous form.
Clastic Sedimentary rock
Cemented fragments & grains from preexisting rocks
slope wetness
Too little- particles can move past another easilytoo much-friction drop to point that material flowsjust right-moisture adds surface tension that stabilizes grains
The degree to which the clasts in a rock are all the same size ot include a variety of sizes.
What are the three kinds of sedimentary environments?
Continental, Shoreline, Marine
What is Chert used for?
Chert, like obsidian and quartz, fractures conchoidally, which makes it an ideal material to construct arrowheads and axe blades
What is a sedimentary rock?
Sedimentary rocks are products of mechanical and chemical weathering
Creep -Solifluction
unconsolidated material slowly moves downhill (mm's/yr) -creep caused by repeated freeze/thaw action
Why is limestone created primarily in warm, shallow water?
Warm water typically holds less CO2 than cold water, which causes the solubility of calcite to decrease.
negligible transport
Limestone [fossiliferous]
diatamacious earth
kills ants
clastic rock fragments
Quartz sandstone
maturely weathered
cemented shells of organisms
the smallest particle size
-between Continental and Marine

includes: beaches and coasts, lagoons, reefs, mangrove swamps (deltas?)
how lithification happens
burial, compaction, cementation
channelized flow transports sediment; sand and gravel fill concave-upward channels; predictable energy
microfossils make up
chalk and chert
calcite silica evaporites rock fragments feldspars
physical weathering
rock break into fragments
a process that squeezes sediments
common sedimentary rock consisting mostly of calcium carbonate (calcite), CaCO3, used as a building stone and in the manufacture of lime, carbon dioxide, and cement.
Geological Dating
relative age and numerical ages
fossiliferous limestone
abundant fossils, reacts to acid
a sedimentary rock texture consisting of broken fragments of preexisting rock
What is fine-grain?
silt and clay (mud)
takes place when dissolved minerals are deposited in the tiny spaces among the sediments.
Organic form of limestone; microscopic shells (coccoliths); used on blackboards; often white in color; often scratched by fingernail
black combustible rock consisting of over 50% carbon. coal is made of a detritus of plants deposited in layers. heat and pressure forced all the volatiles out, leaving a concentration of carbon. accumulates in lush tropical wetland settings. requires deposition in the absence of oxygen.
Chemical maturity

Lowest to greatest: olivine, pyroxene, amphibole, biotite, muscovite, feldspar, quartz

carbonate rock made up predominately of the mineral dolomite, CaMg(C03)2
Sedimentary rocks
What is created when weathering products are redistributed?
The term used to describe materials that are laid down directly by streams is
fossil succession
fossils remnants or traces of once-living organisms are often preserved in sedimentary rocks
Magma pushes into existing rock layers and cools formilng igneous rock. (Volcanoes)
organic rock
are made from once living things
biochemical chert
forms from sediment consisting of silica shells from dead organisms. plankton (microscopic organisms called radiolaria) make shells out of silica. this forms an ooze or gel on the deep ocean floor and solidifies to form a chert.
crumbled shells, looks like a rice crispy treat or oatmeal, bubles with acid
Rock Salt
chemical; composed of mineral halite; transparent to translucent
Water Transportation

o Saltation- particles bouncing (bed load)

o Suspended load- keeps carrying on

o Dissolved load

o Quartz (sand), clay materials, ions

can't see but can feel the "grit"
time for 1/2 of unstable nuclei to decay
poor sorted clast
variety of grain sizes; changing amounts of energy
Environment of deposition
simply a geographic setting where sediment is accumulating.
what is the ultimate end product of chemical weathering?
A sedimentary rock made from silt and clay sized particles in very slow moving water like lakes, swamps, deltas and offshore marines.
clastic rock
(geology) a rock composed of broken pieces of older rocks
sedimentary rocks contain:
coalpetroleum and natural gasFe, Al and Mg
Which sedimentary feature can be used to determine the direction of sediment transport
asymmetrical ripple marks
Angular unconformity
tilted or folded layers get eroded and new layers form on top.
detridal sedimentary rock, p 214
rocks forming from accumulated materials originating and transported as solid particles. The particles can come from mechanical weathering, or chemical weathering, or both.
fissibility, p 216
the property of splitting easily into layers along closely spaced, parallel surfaces, such as bedding planes in shale.
principle of inclusion
fragments included in a host rock are older then the host rock
Three basic sedimentary rock types
Evaporates and biochemical rocks
If ions in a solution is the weathering product, what type of sedimentary rock is formed?
graded bed, p 237
a layer of sediment that has larger particles on the top and smaller particles on the bottom. Graded beds change gradually in grain size from top to bottom.
facies, p 235
a section of a rock unit that has a unique set of characteristics distinguishing it from other parts of the same unit
no cleavage
soft brown coal
clastic crystalline bioclastic
coarsening upward deposits
What are clasts?
rock fragments
Secondary Structures form during...
Gray/brown, has subsurface clay accumulation and abundant plant nutrients. Forms in humid forests (e.g. Eastern US)
unconsolidated particles created by the weathering and erosion of rock
Through weathering, erosion, transport, and deposition sediment becomes what?
sedimentary rock
variety of silica containing microcrystalline quartz siliceous rock occurring as inclusions within limestone.
Distinctive from neighboring rock units
(of deposits, esp. limestones) derived from shell fragments or similar organic remains
present is key to the past
WAY more complex, "truly nuclear", euro stands for nucleus!
Graded Beds
particles within single sedimentary layer gradually change from coarse at the bottom to fine at the top.
Lacking minerals or mineral grains (organic rocks)
Consist of particles (sediment) broken off of preexisting rocks (conglomerate, breccia, sandstone, siltstone, shale)
graded bedding
particle size become progressively heavier and coaser toward bottom
in marine sedimentary rock
What precent of seawater is SALT?
-Unsorted from ice: till
-Sorted from melt water: Outwash (like stream deposits)
elements that have varing number of neutrons
The most abundant type of sedimentary rock is
in an undeformed sequence of layered rock; each bed is older than the one above and younger than the one below
Rock formed from other broken down rocks
Process of sedimentary rocks:
Weathering, Erosion, Deposition, Sedimentation, Cementation
coal and coquina
are 2 organic sedimentary rocks
petrified wood
forms when ash containing silica dissolves in groundwater that passes into trees. the dissolved silica precipitates in wood as cryptocrystalline quartz. the chert will retain the shape of the wood and its growth rings
oolitic limestone
sand grain with a calcite coat/tropical sea
Rain drop marks
Primary structures may also include
crystalline texture, p 228
same as "nonclastic texture"
horizontality and continuity
strata often form laterally extensive horizontal sheets
scour marks
troughs eroded into soft mud by current flow
Reservoir Rock
a porous, permeable rock that will yield petroleum and natural gas in sufficient quantities to make drilling worth-while
Earth is not covered by a thin "veneer" of sediment. T/F
Originally Horizontal
When layers of rock are deposited, they usually start out flat.
What is lithification?
changes sediments into rock and includes compaction/cementation
fined grained detrital sedimentary rocks
siltstone, mudstone, and shale
Other contacs
Unconformities or gaps in the geologic record/ no translation
Weathering (clastic sedimentary process)
Generation of detritus via rock disintegration.
a rock made from bits of mud stuck together
Clastic sedimentary rocks
are composed of weathered bits of rocks and minerals.
mud cracks
when deposits of wet clay dry and contract
cross-bedding, p 235
a principle of relative dating or rock units. A rock or fault is younger than any rock or fault through which it cuts. The older unit had to be there first in order to be changed (intruded into, faulted).
detridal sedimentary rock, p 214
rocks forming from accumulated materials originating and transported as solid particles. The particles can come from mechanical weathering, or chemical weathering, or both.
What are the four classes of sedimentary rocks?
Clastic, biochemical, organic, chemical
oil and natural gas
two basic conditions for an oil reservoir
1. porou, permeable reservoir rock
2. impermeable cap rock
derived from the remains of marine plants and animals
nonmetallic mineral resource
mineral resource that is not a fuel or processed for the metals it contains
Maturity of sediments








What is the usual sediment size?
Sediments can be large like gravel, or small like clay
attack from 3 directions
chemial sediments
precipitation and evaporation
Shale (clay)
Tiny Tiny Grains, Fissile
chemical sediment
ions deposited from solution
solids left when water evaporates
very hard, fine-grained, opaque quartz that sparks when struck with steel
-fine sediments
-often organic and peaty: may form Coral
settling out of the transporting fluid
process of stripping/ peeling away (mechanical effect)
layering that develops as sediments are deposited
Chemical weathering
Occurs when chemical reactions dissolve the minerals in rocks or change them into different chemicals
ripple marks
undulation of sediment surface produced as whind or water move across
symmetric and asymmetric
chemical sedimentary rocks
limestone, dolostone, and evaporites
carbonate rock made up predominately of the mineral dolomite, CaMg(C03)2
very hard, fine-grained, opaque quartz that sparks when struck with steel
well sorted clast
uniform grain size, steady energy
gravels and sands trapped near shore; low energy; very small sediment
a very hard, shiny black metamorphic rock.
Sed Features: Fossils
Any trace of ancient life
Process in which surface materials are worn away and transported from one place to another bu agents such as gravity, water, wind, and glaciers
sedimentary structures
features during or justafter sediment deposition
clues to how and where deposition of sediments occurred
Sedimentary Breccia

(Largest Particles)
Angular fragments, close to surface
strata, p 236
parallel layers of sedimentary rock
due to the movement of ice; takes every grain size so poorly sorted
Organic Sedimentary Rocks
Rocks composed of organic materials. ex: coal
an internal force pushes on the layers and they move into a slant.
Material that was the direct result of living organisms
What is the rock that is most commonly exposed to the surface?
Particle composition
Refers to the makeup of clasts in sedimentary rocks. Clasts may be composed of individual minerals or of rock fragments.
rock whose origin is from the erosion, transportation, deposition, and subsequent lithification of pre-exisiting rocks under conditions at the surface of the earth, or from inorganic chemical reactions, or from lithified accumulation of organic debris
sedimentary rocks
What is compaction?
When layers of small sediments stick together because of pressure
cementation, p 213
one of the ways that sedimentary rocks are lithified. Material precipitating from water percolating through the sediment fills up open spaces and glues the sediment pieces into a solid mass.
fossil, p 23
the remains or traces of organisms preserved from the geologic past
Where is an example of poor lithification?
El Morro, New Mexico
grain sizes small to big
clay, silt, sand, pebble, gravel, boulder - cannot see clay or silt grains
what did the paleozoic era begin with?
the appearence of complex life
salt flat, p 224
a white crust on the ground produced when water evaporates and leaves its dissolved materials behind.
How do sedimentary rocks help tell scientists about the past?
they help us know about animals such as dinosaurs and their fossils
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