Sedimentary Petrology Flashcards
a broad scientific discipline that encompasses study of
all kinds of sedimentary rocks, including those that
constitute a relatively small volume of total
sedimentary rocks
sedimentary petrology
the removal of thick layers of sediments
overlying deeply buried by erosion or uplift
unloading
Rocks which form at low temperatures and pressures at the surface of Earth owing to deposition by water, wind, or ice. covers roughly 3/4 of Earth’s surface
sedimentary rocks
steps in forming sedimentary rock
weathering-erosion-transportation-deposition-diagenesis
The chemical alteration, physical, and biological
breakdown of rock during exposure to the atmosphere,
hydrosphere, and biosphere
weathering
types of weathering
mechanical/physical and chemical
the
expansion force of water as it freezes sufficient
to split any mineral or rock
freezing and thawing
– action of organisms, including animals and
plants reduces the size of rocks and minerals
organisms
Differences
in temperature in a rock give rise to differential
expansion and contraction
heating and cooling
Requires the application of some physical force or stress to be applied to the rock
→ No accompanying changes to the composition of rocks
→ Mechanical breakup increases the rock’s surface area and the surface-to-volume ratio
mechanical weathering
Grinding action, or the
rubbing of moving rock against each other.
griding or rubbing
– the disruption of soil results
in the swelling and contracting of soil beds and particles
wetting and drying
→ breakdown of minerals by chemical reactions with water, with chemicals dissolved in water, or with gases in the air.
→progression from less stable minerals to more stable minerals
chemical weathering
- the dissolving of a solid in a liquid
dissolution
process of minerals reacting with water
to form hydroxides, which usually are more soluble than
the original mineral
hydrolysis
weathering is accelerated by the
presence of hydrogen ion in water, such as that
provided by carbonic and organic acids
acidification
– involves the transfer of charged atoms
(ions) of calcium, magnesium, sodium, and potassium between
waters rich in one of the ions and a mineral rich in another
(Most effective in clays)
ion exchange
used in mineral weathering, is both the chemical combination of oxygen with a compound and the change in oxidation number of some chemical element (Reduction is the chemical process in which electrons are gained.)
oxidation and reduction
– combination of a solid mineral or
element with water
hydration
agents of erosion (GIOWW)
Gravity Ice Organism Water Wind
Agents of Sediment Transport (IWW)
Ice Water Wind
Measures smoothness of the sediment grains
roundness
long distance of transport = ______ roundness
rounded
short distance of transport = ______ roundness
angular
Measure of variation in size of sediment
grains
sorting
short distance of transport = ______ sorted
poorly
the geological process where materials, such as sediment, soil, and rocks, that have been transported by wind, water, ice, or gravity, are laid down or settled in a new location.
deposition
long distance transport = _____ sorted
well
stage of diagenesis that is from sedimentation until shallow burial
early diagenesis
Physical, chemical, and biological processes which collectively result in:
→ Transformation of sediments into sedimentary rock
→ Modification of the texture and mineralogy of the rock
diagenesis
stage of diagenesis that is from deep burial to subsequent uplift
late diagenesis
diagenetic process that squeeze or compacts sediments
compaction
diagenetic process in which there is formation of new minerals
authigenesis
diagenetic process that takes place when dissolved minerals are deposited in the tiny spaces among sediments
cementation
Basic end products, that all sedimentary processes are working to reach
quartz sandstone
shale
limestone
= all visible grains, including such ones
is incompletely weathered feldspar from the granodiorite in the simple ideal model
quartz sandstone
all clay sized grains
shale
= all dissolved minerals, including not only
calcite CaCO3, but also halite (table salt NaCl), and gypsum (CaSO4.2H2O) among others
limestone
categories of sedimentary rocks
clastic/siliciclastic rocks
chemical rocks
biochemical rocks
category of sedimentary rocks that is formed by the end products of mechanical weathering. classified according to texture and composition. made up of clast or framework grains, matrix, and cement
siliciclastic rocks
category of sedimentary rocks that is formed by direct precipitation from solution
chemical rocks
category of sedimentary rocks that is formed by biogenic and chemical processes
biochemical rocks
Composed of the mineral calcite (CaCO3 – calcium carbonate)
* They form by both chemical and biochemical processes
* Tend to be mixed together in various combinations in the rocks.
* They are extremely abundant and important.
Carbonates
peat and coal always form in the presence of _________
clastic rocks like sandstone and shale
Composed of SiO2
* Forms from the recrystallized skeletons of “animals” (single celled radiolarians, and glass sponges) or single celled “plants” (cratoms, silicoflagellates
chert
Halite (NaCl) and gypsum (CaSO4.H2O)
*Originally dissolved in sea water
* Sea water evaporates in a closed area, such as a lagoon, the salt concentration becomes very high, supersaturated, and precipitates out
evaporites
coal that has generally lower sulfur content, which makes it attractive for use because it is clean burning
sub bituminous coal
coal ranks
Lignite-Sub bituminous-Bituminous-Anthracite
- Structure found in sedimentary rocks
- Formed during or immediately after deposition
- Reflects different sedimentary processes
- May be used to determine the environment, flow
direction and tops and bottoms of sedimentary rocks
sedimentary structures
coal that is used primarily to generate electricity and make coke for steel industry
bituminous coal
*Formed by the deposition of sediments
*Bed > 1cm
*Lamination <1 cm
stratification
also called as brown coal, mainly used for electric power generation
lignite
Formed by the drying up and shrinkage of muddy sediments
Suggests a terrestrial environment
mudcracks
– alternating light and dark-colored
laminations which reflect changes in season
varves
Gradual change in grain size from bottom to top strata
graded bedding
- Stratifications that are at an angle to the main bedding plane
- Indicates flow direction
cross stratification
formed on top of the bed by the action of waves (symmetric)or currents
(asymmetric)
Indicates flow direction
ripplemarks
→Craters and pothole formed by the impact of rain on sediments
raindrop imprints
A mass of sedimentary rock which can be
defined and distinguished from other by its
geometry, lithology, sedimentary structures,
paleocurrent pattern, and fossils
sedimentary facies
sedimentary environments
terrestrial/continental
transitional (shoreline)
marine
a fan-shaped, terrestrial deposits
* Found at the transition of mountains and plains.
* where there is tectonic movement which maintains high relief between
mountains and plains
* Formed as mountains shed sediment off their flanks, streams carry it away
as alluvium.
alluvial fan
Composed of coarser particles – cannot be carried by suspension
-particles move along by:
1. rolling
2. sliding
3. saltation
bedload
Rivers/streams are elongated bodies of water that flows through
channels
fluvial/river
– describes activity of deposits of
winds
eolian
ability of streams to carry sediments is described by ___________ and __________
competence and capacity
- Formed in depressions or basins with internal drainage or limited flow
- Geometry – circular or elongate in plan view, lenticular (lens-like) in cross section
lacrustine
Two types of channels
meandering and braided
sand transport where large particles are rolled to the surface after coming into contact with saltating particles
creep
sand transport where bouncing and jumping movement of grains. it involves bedload
saltation
sand transport that occurs when fine dust and dirt are lifted into the wind that involves suspended load
suspension
the process of erosion produced by the suspended particles that impact on solid objects.
wind abrasion
form when there is (1) a ready supply of sand, (2) a steady wind, and (3) some kind of obstacle such as vegetation, rocks, or fences, to trap some of the sand
dunes
crescent-shaped dunes. They form in areas where there is a hard ground surface, a moderate supply of sand, and a constant wind
direction.
barchans dunes
unconsolidated, unstratified aggregation of small, angular mineral
fragments, usually buff in color. General believed to be wind-deposited
loess
long straight dunes that form in areas with a
limited sand supply and converging wind directions.
linear dunes
– large fields of dunes that resemble sand with a steep
face in the downwind side, form in areas where there is abundant supply of
sand and a constant wind direction
transverse dunes
– are “U” shaped dunes with an open end facing
upwind. Form in areas with abundant vegetation and constant
wind. Most common in coastal areas.
parabolic dunes
– dunes with variable arms and slip face directions.
Form in areas with abundant and supply and variable wind
direction
star dunes
The largest type of glaciers on Earth.
-Cover large areas of the land including mountain areas.
-Modern ice sheets cover Greenland and Antarctica.
ice sheets or continental glaciers
where ice can be created and remain all year round
snowline
Permanent (on a human time scale) body of ice that shows evidence of downward movement due to gravitational pull.
* Form at or above snowline
glacier
-Relatively small glaciers at higher elevations in mountainous regions
- small glaciers that form valleys
alpine/mountain glaciers
-Are sheets of ice floating on water and attached to land.
-Usually occupy coastal embayments
ice shelve
particle detachment by moving glacial ice
plucking
bowl shaped depressions that occur at the
heads of mountain glaciers
cirques
valleys that once contained glacial ice
become eroded into a “U” shape in cross section
glacial valleys
– long parallel scratches and grooves that are produced by rocks embedded in the ice scraping against the rock underlying the glacier
glacial striation
rock that has a smooth surface produced as a result of fine
grained material embedded in the glacier acting like sandpaper on the
underlying surface.
glacial polish
– if two adjacent valleys are filled with glacial ice,
the ridges between the valleys can be carved into a sharp knife-edge ridge,
aretes
where three or more cirques are carved out of a
mountain, that can produce a sharp peak
horns
a valley that has greater elevation than the
valley to which it is tributary
hanging valleys
narrow inlets along seacoasts once occupied by a fjord glacier.
fjords
general term for glacial deposits
glacial drifts
environments that are at or near the
transition between the land and the sea
transitional environments
Prograding depositional bodies that form at the point where a river drains into a lake or sea
delta
parts of a delta
delta plain-delta front-prodelta
types of delta
river-dominated
tidal-dominated
wave-dominated
Shallow salt water body separated from the deeper sea by a shallow or exposed sandbank, coral reef, or similar feature
-Quiet waters allow fine silt and clays to settle out of suspension, forming sequence of mudstone and shale
lagoon
continuous or broken circle of coral reef and low coral islands surrounding a central lagoon
atoll
Shore of a body of water formed and washed by waves and tides.
Usually covered by sandy or pebbly material
beach
a long narrow coral reef roughly parallel to the shore
separated from it at some distance by a lagoon
barrier reef
Coral reef that is directly attached or borders the shore of an island or
continent.
fringing reef
