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geo 101 - chapter 6

Terms in this set (59)

sedimentary rock consisting of cemented-together detritus derived from the weathering of preexisting rock
clastic (detrital) sedimentary rock
a fragment or grain produced by the physical or chemical weathering of a pre-existing rock
clast
sedimentary rock formed from material (such as shells) produced by living organisms
biochemical sedimentary rock
sedimentary rock (such as coal) formed from carbon-rich relicts of organisms
organic sedimentary rock
sedimentary rocks made up of minerals that precipitate directly from water solution
chemical sedimentary rocks
sedimentary rock types:

broken bits of previous rocks
clastic
sedimentary rock types:

animals shells
biochemical
sedimentary rock types:

plant/animal remnants
organic
sedimentary rock types:

precipitation from water
chemical
coarse-grained sedimentary rock consisting almost entirely of quartz
sandstone
clasts form by disintegration of bedrock into separate grains due to physical & chemical weathering
weathering
___ refers to the combination of processes that separate rock or regolith (surface debris) from its substrate; involves abrasion, falling, plucking, scouring, & dissolution, & can be caused by moving air, water, or ice
erosion
gravity, wind, water, or ice can carry sediment; the ability of a medium to carry sediment depends on the medium's viscosity & velocity
transportation
___ is the process by which sediment settles out of the transporting medium; sediment settles out of wind or moving water when these fluids slow down, because as the velocity decreases, the fluids no longer have the ability to carry sediment
deposition
geologists refer to the transformation of loose clasts into solid rock as ___, a process that takes place in two stages:

- it begins with ___, when the weight of overburden squeezes air or water out from between grains, so the grains can fit together more tightly
- it ends with ___, when minerals (commonly quartz or calcite) precipitate from groundwater & fill remaining spaces between clasts, to form a cement that binds grains together
lithification, compaction, cementation
the names used for clast size, listed in order from coarsest to finest, are:
boulder, cobble, pebble, sand, silt, and mud
___ of clasts indicates the proportion of clasts in a rock that are the same size
sorting
the size, angularity, sphericity, & sorting of clasts depends on the ___ medium (water, ice, or wind), that carried the clasts, & in the case of water or wind, on both the ___ of the medium & the ___ of transport
transporting, velocity, distance
coarse sedimentary rock consisting of angular fragments; or rock broken into angular fragments by faulting
breccia
very coarse-grained sedimentary rock consisting of rounded clasts
conglomerate
a clastic sedimentary rock containing both quartz & feldspar grains
arkose
fine-grained sedimentary rock generally composed of very small quartz grains
siltstone
very fine-grained sedimentary rock that breaks into thin sheets
shale
very fine-grained sedimentary rock that will not easily split into sheets
mudstone
rocks containing calcite &/or dolomite
carbonate rocks
when organisms die, the shells remain & may accumulate; rock formed dominantly from this material is ___
biochemical limestone
___ consists of visible fossil shells or shell fragments
fossiliferous limestone
___ consists of very fine carbonate mud
micrite
___ consists of plankton shells
chalk
biochemical ___ is made from cryptocrystalline quartz, consisting of quartz grains that are too small to be seen without the extreme magnification of an electron microscope
chert
a setting in which sediments accumulate; its character (fluvial, deltaic, reef, glacial, etc.) reflects local conditions
depositional environment
___ depositional environments, those that develop inland, far enough from the shoreline that they are not affected by ocean tides & waves
terrestrial
___ sediments, or non-marine sediments, accumulate either on dry land or under & adjacent to freshwater
terrestrial
when a glacier melts away, the sediment that had been in or on the ice accumulates as ___
glacial till
___ is unsorted & unstratified, it contains clasts ranging from clay size to boulder size all mixed together
till
where slopes decrease & water flow slows, the ___ clasts settle to form gravel & boulder beds, while the stream carriers ___ sediment like sand & mud farther downstream
larger, finer
sedimentary ___ of a mountain stream would include breccia & conglomerate
deposits
a gently sloping apron of sediment dropped by an ephemeral stream at the base of a mountain in arid or semiarid regions
alluvial fan
deposition takes place in alluvial fans because when the stream pours from a canyon mouth & spreads out into multiple channels, friction causes the water to slow down, & slow moving water does not have the power to move ___ sediment
coarse
sediment in alluvial fans may accumulate close to the source, so it will not have undergone much chemical ___
weathering
in very dry climates, few plants can grow & the ground surface lies exposed; strong winds can move dust & sand; the dust gets carried away, & the resulting well-sorted ___ can accumulate in dunes

this, thick layers of well-sorted ___, in which we can find large cross beds, are relicts of desert sand-dune environments
sand, sandstone
rivers transport gravel, sand, silt, & mud; the ___ sediment tumbles along the bed in the river's channel & collects in cross-bedded, rippled layers while the ___ sediment drifts along, suspended in the water
coarser, finer
geologists commonly refer to river deposits as ___ sediments
fluvial
in temperate environments, where water remains at the surface throughout the year, ___ form
lake
in the offshore portions of a lake, the deeper water is relatively quiet, & ___ can settle out to form mud on the lake bed

when lithified, such lacustrine mud turns into ___
clay, shale
a wedge of sediment formed at a river mouth when the running water of the stream enters standing water, the current slows, the stream loses competence, & sediment settles out
delta
at the mouth of streams that empty into lakes, small ___ may form
deltas
small lakeshore deltas contain three components:

topset beds composed of ___
foreset beds of ___ & ___
& ___ bottomset beds
gravel, gravel, sand, silty
___ environments start at the high-tide line & extend offshore, to include the deep seafloor
marine
deposits of an ocean-margin ___ produce a great variety of sedimentary rock types
delta
if you find well-sorted, medium-grained sandstone, perhaps with ripple marks, you may be looking at the remnants of a ___ environment
beach
in deeper water, where wave energy does not stir the seafloor, ___ sediment can accumulate

because the water here may only be a few meters to tens of meters deep, geologists refer to this depositional setting as a ___ environment
finer, shallow-marine
if you see beds of siltstone & mudstone containing marine fossils, you may be looking at ___ clastic deposits
shallow-marine
in ___ settings, where relatively little sand & mud enter the water, warm, clear, nutrient-rich water can host an abundance of organisms with carbonate shells, which eventually become ___ sediment
shallow-marine, carbonate
___ collect sand composed of shell fragments; ___ are sites where carbonate mud accumulates; & ___ consist of coral & coral debris
beaches, lagoons, reefs
shallow-water carbonate environments transform into various kinds of ___
limestone
in the ___ realm, only fine clay & plankton provide a source for sediment
deep-ocean
clay eventually settles out onto the deep seafloor, forming deposits of finely laminated ___, & plankton shells settle to form ___ (from calcite shells) or ___ (from silica shells)
mudstone, chalk, chert
deposits of mudstone, chalk, or bedded chert indicate a ___ origin
deep-marine
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