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Earth Materials > Sedimentary Rocks > Flashcards

Sedimentary Rocks Flashcards

1
Q

Sedimentology =

A

Processes that weather, erode, transport and deposit sediments or depositional environments

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2
Q

Sedimentary petrology =

A

Characteristics and origins of sedimentary rocks

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3
Q

Stratigraphy =

A

Complex distribution of sedimentary rock record in space and time

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4
Q

Weathering =

A

A combination of processes by which pre existing rocks physically disintegrate and chemically decompose to form soils/loose classy/dissolved components

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5
Q

Slowest weathering

A 
Quartz
Clay
Muscovite
K feldspar
Biotite
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6
Q

Fastest weathering

A 
Halite
Calcite
Olivine
Plagioclase
Pyroxene
Amphibole
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7
Q

Components of a sedimentary rock

A

1) grains/clasts
2) matrix (mud/micrite)
3) cement (silica/sparite)

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8
Q

Maturity, indications:

A

Low amounts of clay
Well sorted (grain size not variable)
Well rounded

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9
Q

Immature-submature; locations

A

Fluvial overbank

Alluvial fab

Marine turbidite fans

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10
Q

Submature-mature; locations

A

Fluvial channel sands

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11
Q

Mature-super mature; locations

A

Aeolian dunes

Beach sands

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12
Q

Transporting agent =

A

Mechanisms responsible for movement from where it is weathered to where it is deposited

Rolling/sliding/saltation/suspension

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13
Q

Diagenesis =

A

All changes (NOT METAMORPHIC) in texture, composition and physical properties that occur in sedimentary rocks after they are deposited

  • compaction
  • recrystallisation
  • cementation
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14
Q

Conglomerate/breccia classification

A

ORTHOCONGLOMERATES
- matrix <15%
- grain supported
Can be OLIGOMICT (single mineral) or POLYMICT (multiple minerals)

PARACONGLOMERATES

  • matrix >15%
  • matrix supported

Gravel/sand/mud triangles

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15
Q

Sandstone classification

A

Quartz arenites

Arkoses (feldspar)

Lithic arenites (lithics)

Wackes

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16
Q

Quartz arenites - location

A

Shallow marine

Wind blown dune deposits

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17
Q

Arkoses location

A

Alluvial fan
Delta deposited
Desert arkose
(MINERALOGICALLY IMMATURE, TEXTURALLY SUPERMATURE)

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18
Q

Lithic arenites location

A

Alluvial deposits
Orogenic clastic wedges
Turbidites

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19
Q

Wackes location

A

Sediment gravity flows

Submarine fan complexes

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20
Q

Different types of carbonates (triangle)

A

Ca ARAGONITE

Mg MAGNESITE

Fe SIDERITE

DOLOMITE = mixture

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21
Q

Controls on carbonate deposition

A

Temperature

Pressure

Agitation
- CO2 absorbed from atmosphere = increases deposition

Organic activity

Sediment masking/clogging
- slow terrigenous accumulation rates = increases deposition

Light

CCD

22
Q

Limestone components

A

1) grains - ALLOCHEMS

ORTHOCHEMS

2) matrix
- micrite

3) cement
- sparite

23
Q

Calcite vs aragonite seas

A

Calcite

  • early palaeozoic and mid to late Mesozoic
  • warm, shallow marine

Aragonite

  • mid palaeozoic and early Mesozoic and cenozoic
  • cool marine
24
Q

Non skeletal grains

A

1) Coated = ooids/peloids
2) aggregates
3) clasts
4) non carbonate grains

25
Q

Skeletal grains

A

Foraminifers

Corals

Bryozoans

Brachiopods (clear fragment in middle)

Mollusks

Echinoderms

Ostracods

26
Q

Friable =

A

Tendency of a solid substance to break into smaller pieces under duress or contact, especially by rubbing

Opposite = INDURATE

27
Q

Glauconite

A

Shallow marine material

Easily weathered

Presence suggests little transport before deposition and slow rates of accumulation

28
Q

When do cements form?

A

During diagenesis

29
Q

Limestone classification:

MUDSTONE

A

<10% grains

Mud supported

30
Q

Limestone classification

WACKESTONE

A

> 10% grains

Mud supported

31
Q

Limestone classification

PACKSTONE

A

Contains mud

Grain supported

32
Q

Limestone classification

GRAIN STONE

A

Lacks mud

Grain supported

33
Q

Limestone classification

BOUNDSTONE

A

Original components bound together during deposition

34
Q

Limestone classification

CRYSTALLINE CARBONATE

A

Depositional texture not recognisable

35
Q

Stages of cementation

A

First stage = drusy (needle like crystals radiating away from grains)

Second = blocky filling void

(Can have bladed in between)

36
Q

What does the presence of mud (matrix) indicate?

Carbonate vs Siliclastic

A

Carbonate:
- prolific algae growth

Siliclastic:
- settling from suspension

37
Q

Effect of periodic exposure?

Carbonates vs siliclastics

A

Carbonates:
- intensive diagenesis, especially cementation and recrystallisation

Siliclastic:
- relatively unaffected

38
Q

Pelagic sediments

A

1) pelagic rain and marine snow
2) calcareous ooze
3) siliceous ooze

39
Q

Pelagic sediments =

A

Mixture of non biogenic (clay), siliceous biogenic (radiolarians/diatoms) and calcareous biogenic (nannofossils) sediments that are organic matter rich

40
Q

Pelagic rain and marine snow

A

Mostly fecal pellets
Accelerated sinking
- week or two rather than years

41
Q

Calcareous ooze; depends on…

A

1) production rate of calcareous organisms in overlying water
- surface water depleted in CO2 due to photosynthesis (PRIMARY PRODUCTIVITY) but increases as O2 decreases due to respiration

2) dilution by other types of particles
3) CCD (accumulates above)

Covers 48% of ocean floor

Undergoes small scale cycles

42
Q

Ooze =

A

Deep sea sediment with more than 30% biogenic material

Accumulates slowly (1-6cm/ky)

43
Q

Calcareous ooze small scale cycles:

A

1) carbonate litho/micro facies
2) nodular/non
3) bioturbated/non
4) carbonate rich/poor
5) carbonate/clay
6) carbonate/chert

CYCLICITY IN CORES FOLLOWING MILANKOVITCH CYCLES (precession)

44
Q

Siliceous ooze

A

CHERT

Negative correlation with calcareous

14% deep sea floor surface covered by siliceous ooze

45
Q

Red clay

A

Aeolian origin

46
Q

Glacial sediments

A

DROPSTONES

Highly laminated mud sediments interspersed with horizons of very coarse material

Heinrich events - cyclically with glaciation/deglaciation

47
Q

Varve =

A

Thin pair of clay/silt layers with contrasting colour/texture which represent a deposit in a single year in a lake

48
Q

Non laminated mudstone vs laminated mudstone

A

Siltstone/ laminated siltstone

Mudstone/mudshale

Claystone/clayshale

49
Q

Black shale

A

> 1% TOC

50
Q

Oil shale

A

> 20% TOC

51
Q

Coal

A

> 50% TOC

N.B. Terrestrial

Earth Materials (3 decks)

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