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Geology 381 > Lab Final > Flashcards

Lab Final Flashcards

1
Q

What are siliciclastic or terrigenous rocks?

A

Siliclastic - dominated by silicic fragments
Terrigenous- made up of detritus eroded material eroded under non-marine conditions from pre-existing rock terranes

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2
Q

What are carbonate Intraclasts?

A

Fragments of calcium carbonate material that has been partially lithified and then broken up and reworked to form a clast which is incorporated into the sediment

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3
Q

What are litho-or Extraclasts?

A

When evidence suggests that the clasts of limestone had been eroded outside their depositional basin, he clasts prododuced are lithoclasts/extraclasts

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4
Q

What are the Dunham classifications for limestones?

A

Mudstone
Wackestone
Packstone
Grain stone
Boundstone
Crystalline
Floatstone
Rudstone
Baffle stone
Bindstone
Framestone

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5
Q

How do you classify a mudstone?

A

-depositional texture recognizable
- original components not bound together during deposition
-contains lime mud
-mud supported
-less than 10% grains

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6
Q

How do you classify a wackestone?

A

Depositional texture is recognizable
Original components are not bound together during deposition
Contains lime mud
Mud supported
More than 10% grains

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7
Q

How do you classify packstone?

A

Original components not bound together during deposition
Contains mud
Grain supported

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8
Q

How do you classify grainestone?

A

Orginal components not bound together during deposition
Lacks mud and is grain supported

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9
Q

How do you classify boundstone?

A

Original components were bound together

3 sub categories; bafflestone, bindstone, and framestone

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10
Q

How do you classify bafflestone?

A

Orginal comments were organically bound during deposition by organisms that acted as baffles (flow directing or obstructing)

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11
Q

How do you classify bindstone?

A

Original components were organically bound during deposition by organisms that encrusted and bound

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12
Q

How do you classify framestones?

A

Their Original components are organically bound during deposition by organisms which built a rigid framework

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13
Q

How do you classify a floatstone?

A

The Orginal components are not organically bound during deposition
More than 10% of grains are greater than 2mm components
Matrix supported

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14
Q

How do you classify rudstone?

A

Orginal components not organically bound during deposition
Greater than 10% of grains are greater than 2mm
Grain supported

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15
Q

What are the skeletal grains?

A

Bivalves, gastropods, brachiopods
Stromatoporoids
Stomatalites
Corals
Bryozoa
Crinoids

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16
Q

What are the non-skeletal grains?

A

Intraclasts
Ooids and their larger cousin, pisoids
Peloids or pellets

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17
Q

How do you classify a carbonate rock?

A

Name based on the most abundant grain type and then the Dunham classification

18
Q

How do you describe a carbonate rock?

A

Grain types in order of abundance
Description of each grain type
Micrite and/or sparry calcite cements (and percent)
Grain vs matrix supported

19
Q

What is a crystalline limestone?

A

Rocks mainly composed of calcium carbonate
Classified by Dunham’s system

20
Q

What is a crystalline dolostone?

A

Coarse dolomite crystals
Can be any colour
Commonly associated with styrolites, bugs, and fractures
The Orginal texture is commonly not persevered

21
Q

What is a zebra dolostone?

A

Coarse dolomite crystals
Alternating dark and light bands of dolomite
Dark bands are microcrystalline and rich in organic matter
Light bands are coarse dolomite spar

22
Q

What is dolomitization?

A

Orginal Calcite grains and matrix/calcite spar of limestones are converted into dolomite
During limestone diagenesis

23
Q

What are evaporites?

A

Chemical rocks comprised of minerals precipitated from saline or hyper saline solutions
Most commonly: halite, sylvite, anhydride, gypsum, barite, calcite, and dolomite

24
Q

What are the requirements for precipitation?

A

1) the Bain must be hydrologically closed or restricted. (Rate of water flowing in is greater than rate of outflow

2) hot, arid climates which facilitate high rates of water evaporation from the basin

25
Q

What is anhydride?

A

Common evaporites, a calcium sulphate
Have different forms: nodular, mosaic, chicken wire, laminated, massive, and enterolithic.

26
Q

What are sulphates?

A

Gypsum and anhydride, barite

27
Q

What are chlorides?

A

Halite

sylvite

28
Q

What is halite?

A

Translucent or clear to milk or cloudy white and grey varieties
Rock salt, has a salty taste
Cubic crystal form and precipitate from saline to hyper saline basins experiencing very high rates of evaporation

29
Q

What is sylvite?

A

Reddish colour
Potash salt, bitter tasting
Cubic crystal form and precipitate out from saline to hyper saline brines in basins experiencing high rates of evaporation

30
Q

What are stromatolites?

A

Laminated oregano-sedimentary structures formed by trapping and binding carbonate particles on a surficial blue-green algal mat
Supra and intertidal zones

31
Q

What are the four main stromatolithic growth habits?

A

Cryptagal laminates - planar to irregular or crinkly algal laminae. Associated with desiccation features. Shallow water

Laterally linked hemispheroids - more regular laminae that appear folded

Vertically stacked hemispheroids - domes or columns.

Oncolites - rounded, growth pattern. Formation due to the rolling up of algal mats or crypt algal lamanites into balls

32
Q

What are the cavity structures?

A

Openings or pore spaces
Can be filled with sediment and then cement to form fenestrae or geopetal

33
Q

What is fenetrae?

A

Small cavities or openings in carbonate rocks
Can be filed with sediment or spar
Can be left open

34
Q

What are geopetal structures?

A

The filing in of cavities by sediment or cement
Common within and beneath shells and other skeletal grains

35
Q

What are styrolites?

A

Pressure dissolution features often found in carbonates
Jagged, irregular seams that separate two carbonate blocks

36
Q

What is found in a peritidal depositional environment?

A

Wackestone, mudstone

37
Q

What is found in a lagoonal depositional environment ?

A

Algal bindstone

38
Q

What is found in a reef depositional environment

A

Boundstone, floatstone, packstone

39
Q

What is found in a fore reef and slope depositional environment

A

Stromatoporoidal boundstone

40
Q

What is barite?

A

Common sulphate
Forms in arid climates through displacing growth
“Desert rose”
Pink due to ion oxide impurities

Geology 381 (3 decks)

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