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Sedimentology > Week 1 > Flashcards

Week 1 Flashcards

1
Q

Sedimentology =

A

Study of processes that create sediments and dynamic environments where they accumulate

~75% rocks are sedimentary

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2
Q

Uniformitarianism =

A

Present is the key to the past

but e.g. climate = changed?!

Used in palaeoclimatography, palaeogeography, transgression, regression, fossils

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3
Q

Rock cycle

A

Weathering

Transportationg

Deposition

Burial

Metamorphism/Magma

Uplift

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4
Q

Stratigraphy =

A

Layers of rock

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5
Q

Transgression =

A

Rising SL

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6
Q

Regression =

A

Falling sea level

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7
Q

The 5 basin settings

A
  1. Rift
  2. Intracratonic
  3. Passive margin
  4. Foreland
  5. Strike-slip
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8
Q

Rift basin

A

Crust thinned as stretched
Rift grows = crust blocks on fault border slip
–> low areas and narrow mountain ridges

Continental/marine

e.g. E African rift

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9
Q

Intracratonic basin

A

Interiors of continents (circular/oval)

Slow subsidence due to thermal sag over previous rifting areas

Continental BUT flooding from adjacent oceans = epicontinental seas

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10
Q

Passive margin basin

A

Along continent margins (NOT tectonic)
Underlain by former oceanic crust rift
Thermal relaxation/subsidence

Carbonate and clastic (10-20km thick)

e.g. Gulf of Mexico along Southern US

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11
Q

Foreland basin

A

Adjacent and // to mountain belts
Compressional tectonics = downward flexing of lithosphere due to weight of adjacent mountain belt

Deep marine –> continental (erosion of mountains) - thickness >10km

e.g. Persian Gulf due to Zagros Mountains of Iran

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12
Q

Strike-slip basin

A

“Pull apart” basin

Continental/marine

e.g. San Andreas, California

North Anatolian Fault, Turkey

Tabernas Basin, SE Spain

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13
Q

Uses for sedimentology

A

Hydrocarbons

Placer diamonds
(eroded/transported by sedimentary processes)

Groundwater

BIFs; iron ore

Limestone mining

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14
Q

“Liberation of sediment flux”

A
  1. WEATHERING AND EROSION
    - chemical/physical
    - uplift
    - climate
    - lithology
    - vegetation
  2. SEDIMENT YIELDS
    = total amount of sediment exported from drainage basin in given period of t (/km2/a)
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15
Q

Denudation =

High/low???

A

Erosion

High levels due to orogenic belts/rivers
e.g. Brahmaputra
Also due glaciers; transport sediment (powerful) + no vegetation to stabilise

Low due to old cratons/low lying areas e.g. Africa

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16
Q

Sediment routing system =

A

Source –> sink pathway along different trajectories

e.g.

RIVER BED; short transit times, brief sediment storage

BARS/FLOOD PLAIN: long transit time, long sediment storage

Storage represents buffering of incoming sediment flux

17
Q

Why are mass flows important?

A

Transport significant amounts of material

18
Q

Types of mass flow from slow to fast

A

Creep

Slump

Mud flow

Rock/debris slide

Rock/snow avalanche

Rock/debris fall

19
Q

Angle of repose =

A

35’

Past this = landslide

20
Q

What causes thermohaline circulation?

A

Density - due to salinity/T

21
Q

Contourite sediments =

A

Reworked turbidite sediments due to thermohaline circulation

N.B. No record during upper cretaceous b/c no bottom water circulation

22
Q

What happens after sediment deposition?

A

Burial, lithification, compaction

N.B. Mudrocks 80% water!!!

23
Q

Types of sediment

A

BIOGENIC

CLASTIC

CHEMOGENIC

VOLCANICLASTIC

ORGANIC

24
Q

Biogenic sediment

A

Skeletal fragments of calcite/aragonite (and direct option)

Limestone/dolomite

25
Q

Clastic sediment

A

Fragments of rock eroded and deposited together

Conglomerates/breccias/sandstone/mudstone

26
Q

Chemogenic sediment

A

Supersaturated and inorganically precipitated

Evaporites

27
Q

Volcaniclastic sediment

A

Fragments of volcanic material

Agglomerate, lapilli-stone, ignimbrite, lahars

28
Q

Organic sediment

A

Accumulation/lithification of organic debris

Coal/oil shales/shale gas

Sedimentology (9 decks)

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