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W5 handout sedimentary rocks class notes Flashcards

1
Q

three factors when looking at sedimentary rocks

A

source, slope, sink

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2
Q

source area

A 
factors such as 
composition of source area
climate
geological setting
influence how source material will respond to Earths reactive atmosphere
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3
Q

move down slope

A

Processes (wind, water, ice) serve to move weathered debris ( sediment) down slope until deposited

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4
Q

sink

A

sediment deposited in environment of accumulation or sink

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5
Q

Sedimentary Rocks make up

A

80% of rocks exposed on earth surface

layer of sedimentary rock relatively thin

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6
Q

stratified

A

sedimentary rocks are layered

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7
Q

beds or laminae

A

greater than 1 cm thick: beds

less than 1 cm: laminae

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8
Q

depositional unit means

A

accumulation of material > erosion

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9
Q

beds and laminae are seperated by

A

bedding or lamination planes

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10
Q

each surface represents

A

a change in conditions

ex change in source of material, particle size, energy of transporting agent

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11
Q

loss of recorded time

A

time is lost at bedding planes bcs erosion
bedding planes are all disconformities
major losses of time: unconformities

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12
Q

lithification

A

sediment is converted to sedimentary rock by lithification

processes: cementation and compaction

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13
Q

cementation

A

prcipitation of a chemical cement that binds the individual particles together
effective with coarser grained rocks

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14
Q

compaction

A

grains are forced together as a result of increased load pressure
more effective with finer clastic sedimentary rocks

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15
Q

Diagenesis

A

processes that act to modify the sediment and sedimentary rock after its buried
diagenesis may grade into metemorphism if temperature and pressure increase sufficiently

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16
Q

two broad cateegories of sedimentary rocks

A

clastic and chemical

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17
Q

clastic classified as

A

particles carried as solids by the slope agents

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18
Q

chemical classified as

A

ions transported in solution until they precipitate
such as limestomes (calcite and dolomite)
sulphates and salts

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19
Q

clastic bigger than sand sized

A

(bigger than 2mm)
conglomerates (rounded fragments)
breccia ( angular fragments)

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20
Q

clastic sand sized

A

(1/16 to 2mm)
quartz arenite- quartz is dominant component
arkose- feldspar is dominant componentt
litharenite- rock fragmeents are dominant component

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21
Q

clastic silt sized

A

1/256 to 1/16 mm)

silt stones

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22
Q

clastic clay sized material

A

(1/256 mm)
shale - rock is fissle, cleavage of clay minerals are parallel to each other, imparts a tendency to split into thin layers
mudstone- non fissle, cleavages not parallel,
rock has a blocky fracture

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23
Q

three major types of sedimentary rocks

A 
coarse clastics (conglomerates, breccias, sandstones) 
fine clastic ( shale and mudstone) 
chemical sedimentary rocks
24
Q

compositional maturity ( quartz)

A

the greater the amount of quartz in a coarse clastic sedimentary rock the higher the compositional maturity

25
common minerals react to form clay if
climate conditions are favourable and source area is stable
26
Sorting
set of processes that tend to concentrate particles of similar size
27
quartz abrasion when transported
when quartz transported --> change in shape due to abrasion --> grains bang together --> sharp corners and rounded edges
28
Feldspars abrasion when transported
Feldspars may cleave and retain angular shape when transported
29
Supermature means
compositionally and tecturally mature | ex. rock consisting of clastic grains the same size, containing majorly well rounded quartz grains
30
immature composition
mixture of sand sized angular quartz grains and clay minerals
31
two types of maturity
mineralogical maturity | textual maturity
32
mineralogical maturity
extent to which the unstable minerals have been destroyed by weathering
33
textual maturity
measures the availability of persistent currents that are needed to produce sorting and rounding of quartz
34
wind water and ice as producing mature sediments
wind and water produce mature sediments if slope agents are persistent ice tends to be unselective, glacial deposits are characteristically poorly sorted and immature
35
two other aspects of sedimentary rocks
porosity and permeability
36
porosity
percent of open space in the rock
37
permeability
extent to which the pores are interconnected so fluids can flow through the rock
38
stored in rocks
hydrocarbons and other liwuids (water) stored in rocks that are porous and permeable smth can be porpous but not permeable (ex. sponge)
39
if permeability changes
fluids may be trapped in rock unit creating a reservoir
40
cementation
reduced bot porosity and permeability of a coarse clastic rock
41
shales and mudstone (permeability and porosity)
low permeability but moderate porsity | may form permeability barriers that prevent fluids from escaping from a reservoir
42
aeolian grain marks
``` wind transported (aeolian) grains move through air and impact grains --> pits pitting increases to give "frosted" look ```
43
ripples, assymetric and symmetrical
ripples (beach area) cusp shaped ridges location of ancient beaches so where marine met terrestrial environment symmetry: back and forth of beach current (oscillation ripples) assymetrical ripples: formed by streams etc with steep side pointing down slope and gentle side up slope
44
cross beds as indicators
very thin beds and low velocity --> velocity increases --> some grains are picked up, carried in suspension slope agent --> grains inclined with respect to horizontal plane --> cross beds cross beds record direction of transport beds point down stream
45
determine which side of bed was up
geopetal structures oscillation ripple marks form on top of beds deposited along beach coarsest grains in graded bde were deposited on bottom of bed
46
lacustrine
sediment deposited in a lake
47
sediment in transition zone between continent and ocean
``` sediment can be transported to deep ocean however accumulation low more accumulation in transition zone deltas beaches barrier islands ```
48
Pelagic component, 1 way of depositing sediment
volcano erupts --> ash transported --> eventually accumilates on ocean floor --> PLANKTON ETC. DIE AND SHEÖLS ACCUMULATE ON SEA FLOOR --> PELAGIC COMPONENT
49
turbidity current, 2 way of depostitng sediment
Debris transported rapidly down slope by a turbidity current --> accumulatesat the foot of continental slope --> submarine fan currentsc haracteristically develop along active continental margins where earthwuake and volcanic eruptions may trigger rapid underwater downslope movement of debris trubdity currents scour out submarine canconcy, sediment fans out --> deposited as they exit canyon
50
sediments in the deep ocean
``` coarse sandstones (with fossils), clay minerals, shells of marine organisms no calcium carbonate past 4000m, only accumulates in warmer, shallow water ```
51
sediment at beach
continental sediment is coarsest beach sediment is finer well sorted, offshore material is even finer frained
52
transgression of the marine environment over what had been a continental environment
relative rise in sea level resulting in n encroachment
53
regression
relative drop in sea level resultimng in migration of continental environment over what had been the marine environment
54
trans and regression caused by glaciers
short lives (1000yrs) gressions may be casued by glaciers glaciers advance --> sea level lower glaciers retreast --> sea level higher
55
sea floor spreading leads to sea level rise
rapid sea floor spreading --> enlargement of mid ocean ridge --> increase in volume of ridge causes ocean water to enroach on land if rate of spreading slows ridge occupies less volume and ocean water moves away from continent

Surface Processes (14 decks)

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