Geology - Carbonates Unit 4

Front 1

What are the components of carbonate rock?

Back 1

Skeletal grains, pores, cement, matrix, non-skeletal grains

Front 2

What are the 2 types of porosity classification?

Back 2

Descriptive (Choquette & Pray, 1970)
Interpretive/Descriptive (Lucia 1995)

Front 3

In descriptive porosity(Choquette & Pray, 1970), what are the 3 basic types?

Back 3

Fabric Selective, Not Fabric Selective, Fabric selective or not

Front 4

What are the 7 types of porosity within Fabric Selective?

Back 4

interparticle, intercrystal, intraparticle, moldic, fenestral, shelter, growth-framework

Front 5

What are the 3 types of porosity within Not Fabric Selective?

Back 5

fracture, channel, vug, cavern

Front 6

What are the 4 types of porosity within Fabric Selective or Not?

Back 6

breccia, boring, burrow, shrinkage

Front 7

What kind of porosity is caused when an organism dissolves?

Back 7

moldic

Front 8

What kind of porosity is between grains or within grains?

Back 8

inter/intraparticle and intercrystal

Front 9

In terms of fluid extraction, what is more preferred, inter/intraparticle or porosity?

Back 9

interparticle = good

intraparticle & moldic = bad

Front 10

What kind of porosity tends to have good permeability?

Back 10

fracture porosity

Front 11

What are the two categories of porosity that Lucia devised?

Back 11

Interparticle: intergranular & intercrystalline

Vuggy: separate vugs & touching vugs

Front 12

Define Lucia's interparticle porosity.

Back 12

Interparticle: pore space located between particles but not significantly larger than the particles of the rock.

Front 13

Define Lucia's vuggy porosity.

Back 13

Vuggy: pore space larger than or within the particles of the rock.

Front 14

Define Lucia's separate vug porosity.

Back 14

Separate Vug: vuggy pore space connected through the interparticle pore space.

Front 15

Define Lucia's touching vug porosity.

Back 15

Touching Vug: vuggy pore space that forms an interconnected pore system.

Front 16

What do you need to use to determine Lucia's classification?

Back 16

1) porosity type and percent

2) size of particles that control porosity

Front 17

What are two "important" features that are looked for in dolostones?

Back 17

grain size and porosity

Front 18

Fundamental Rock Fabrics for Petrophysical Quantification:
Class 1

Back 18

grainstone, dolograinstone, large crstalline dolostone

Front 19

Fundamental Rock Fabrics for Petrophysical Quantification:
Class 2

Back 19

grain-dominated packstone, grain-dominated fine/medium crystalline dolopackstone, medium crystalline mud-dominated dolostone

Front 20

Fundamental Rock Fabrics for Petrophysical Quantification:
Class 3

Back 20

mud-dominated fabrics (packstone, wackestone, mudstone), fine-crystalline mud-dominated dolostone

Front 21

Walther's Law

Back 21

states that the vertical succession of facies reflects lateral changes in environment. Conversely, it states that when a depositional environment "migrates" laterally, sediments of one depositional environment come to lie on top of another.(

Front 22

What is a facies?

Back 22

a body of rock with specified characteristics. Ideally, a facies is a distinctive rock unit that forms under certain conditions of sedimentation, reflecting a particular process or environment.

Front 23

What is the goal of facies analysis?

Back 23

to reduce a continuous spectrum of deposits into a finite set of bins (facies)

Front 24

Name 7 different facies

Back 24

lithofacies, sedimentary facies, environmental (or depositional) facies, diagenetic facies, biofacies, petrofacies, rock-fabric facies

Front 25

What is a lithofacies?

Back 25

used in ancient species; the aspect, appearance and characteristics of a rock unit, usually reflecting the conditions of its origin.

Front 26

What are environmental facies?

Back 26

used in modern systems; refers to the environment or area in which a rock was formed

Front 27

What is a depositional system?

Back 27

it is a 3D association or assemblage of facies genetically linked by active (modern) or inferred (ancient) environmental and sedimentary processes.

Front 28

A platform-margin sand-shoal depositional system is composed of what 3 dominant facies?

Back 28

1) shoal-crest facies
2) washover-fan facies
3) tidal channel facies

Front 29

What should facies descriptions include?
1) fossil or non-skeletal allochem modifier
2) Dunham name

Back 29

3) physical & biological (trace fossils) sed structures
4) grain size and sorting
5) mineralogy 6) presence/ absence of cement types
7) porosity and types
8) interpretation of dep. envr.

Front 30

Examples of useful facies names: cross-stratified ooid-peloid grainstone; massive fusulinid-peloid wackestone;

Back 30

laminar stromatoporoid boundstone; fine-medium-grained massive peloid packstone; bioturbated brachiopod packstoe

Front 31

Interpretation of Depositional Environment, Fossil Assemblage:
Platform interior, restricted (elevated salinity)

Back 31

- low diversity, monospecific opportunists
- Stromatolites, algal mats
- other green algae

Front 32

Interpretation of Depositional Environment, Fossil Assemblage: Mid platform - open shallow shelf

Back 32

- high diversity
- brachs, bivalves, crinoids, bryozoans, various green algae, corals --> all common

Front 33

Interpretation of Depositional Environment, Fossil Assemblage: Platform margin - reef system

Back 33

- corals, stromatoporoids, green & red algae, rudist clams, sponges, stromatolites
- high diversity index, large size, organisms that show attachment
- massive highly calcified structures for wave resistance

Front 34

Interpretation of Depositional Environment, Fossil Assemblage: Fore-Slope

Back 34

- brachs, crinoids dominant, platy stromatoporoids or corals for maximizing light penetration

Front 35

Interpretation of Depositional Environment, Fossil Assemblage: Basin

Back 35

Only delicate forms, brachs can live in muddy substrate, some increase in pelagic fall-out

Front 36

Interpretation of Depositional Environment, Non-Skeletal Allochems: Peloids

Back 36

- not too good for any specific setting, occur widely by local generation and also get transported

Front 37

Interpretation of Depositional Environment, Non-Skeletal Allochems: Ooids - a critical energy indicator

Back 37

- high energy shelf margin
- tidal currents
- mixing of hypersaline platform-top water with open ocean water

Front 38

Interpretation of Depositional Environment, Non-Skeletal Allochems: Pisolites - two general types

Back 38

- soil pisolites indicating exposure, erosion, and rainfall
- depositional formation in marine vadose zone associated with teepee formation

Front 39

Interpretation of Depositional Environment, Non-Skeletal Allochems: Mechanical Clasts, intraclasts (two different scenarios)

Back 39

- ripped up mud-cracked tidal flat
- rip-up flat -pebble conglomerte from storm-generated erosion on the shelf

Front 40

Interpretation of Depositional Environment, Non-Skeletal Allochems:Aggregate grains or grapestone

Back 40

- low energy subtidal shelf

Front 41

Interpretation of Depositional Environment, Depositional Texture: Grainstone - high-energy

Back 41

- two typesmassive burrowed and cross-stratified (<-- higher energy)

Front 42

Interpretation of Depositional Environment, Depositional Texture: Grain-Dominate Packstone

Back 42

- typically a good indicator of mixed environment, probably a grainstone that was shifted into a lower energy environment and then burrowed to get mud mixed within.

Front 43

Interpretation of Depositional Environment, Depositional Texture: Mud-Dominated Rocks, Packstones & Wackestones

Back 43

- lower energy settings, large range of water depths from subtidal lagoons & tidal flats to outer shelf, slope, and toe-of-slope

Front 44

Interpretation of Depositional Environment, Depositional Texture: Mudstones occur at opposite ends of spectrum

Back 44

- mudstones common in tidal flats where too restricted for fossils or other burrowing forms
- mudstones occur also in deep water basinal settings

Front 45

Interpretation of Depositional Environment, Sedimentary Structures: Tidal Flats

Back 45

- current laminations, algal lamination, mud cracks, rip-up clasts, fenestral lamination, low-relief stromatolites

Front 46

Interpretation of Depositional Environment, Sedimentary Structures: Shelf

Back 46

- cross-bedded sands, storm deposits, burrowing

Front 47

Interpretation of Depositional Environment, Sedimentary Structures: Reef

Back 47

- few sedimentary structures, massive framestones or bafflestones, early marine cement

Front 48

Interpretation of Depositional Environment, Sedimentary Structures: Slope

Back 48

- soft sediment folds, breccia deposits, graded bedding, turbidites

Front 49

Interpretation of Depositional Environment, Sedimentary Structures: Basin

Back 49

- thin bedded mudstone, fine mm-lamination, absence of burrowing

Front 50

What are the major facies in shorezone systems?

Back 50

eolian
tidal flat
barrier island/ beach/ tidal channel/ inlet
upper and lower shoreface

Front 51

Define:
supratidal
intertidal
subtidal

Back 51

- above mean high tide, exposed almost all the time
- between high tide and low tide exposed and flooded on a ddaily basis
- below mean low tide, not exposed

Front 52

Tidal Flat Deposits

Back 52

Tidal flats are reverse deltas. Sediment from the subtidal factory is transported onto the flats through daily tides and storms. They accumulate sediemnt and then build or prograde across the shelf. It is a classic "upward shallowing cycle" of carbonate rocks.

Front 53

Intertidal-Supratidal Sediments, low energy tidal flats, examples are...

Back 53

channels, levees, beach ridges, ponds, intertidal flats

Front 54

Common Exposure Structures, Supratidal:

Back 54

tepee, mud cracks, root tubules and burrows (upper subtidal to supratidal)

Front 55

Common Exposure Structures, Intertidal:

Back 55

irregular fenestrae (and key-hole vugs), root tubules and burrows (upper subtidal to supratidal)

Front 56

Common Exposure Structures, Subtidal:

Back 56

root tubules and burrows (upper subtidal to supratidal), 'hardground' fenestrae

Front 57

Stromotoporids come from...

Back 57

calcareous sponges

Front 58

Whitings are believed to be caused by...

Back 58

aragonite precipitation aided by biologic activity

Front 59

Cool water carbonate build-ups are common on...

Back 59

ramps

Front 60

Reef building rudists are common to what geologic age?

Back 60

cretaceous

Front 61

Steep rimmed carbonate platforms generally show what kind of stacking pattern?

Back 61

aggradation

Front 62

What are the 4 major facies tracts in carbonate shorezone systems?

Back 62

eolian (like clastics, early cementation)
barrier island/beach/tidal channel/inlet (like clastics)
upper & lower shoreface (like clastics)
Tidal flat: supra, inter, sub

Front 63

Tidals flats _____ sediment and then build up OR ______ across the shelf.

Back 63

Tidals flats accumulate (aggrade) sediment and then build up OR prograde across the shelf.

Front 64

Tidal flats show the classic __________ of carbonate rocks.

Back 64

Tidal flats show the classic "upward shallowing cycle" of carbonate rocks.

Front 65

Inter/Supratidal sediments on _________ are from beaches with windward margins and recieve skeletal sands from reef and backreef settings.

Back 65

Inter/Supratidal sediments on HIGH ENERGY SHORELINES are from beaches with windward margins and recieve skeletal sands from reef and backreef settings.

Front 66

Inter/Supratidal sediments on _________ are from channels, levees, beach ridges, ponds, and intertidal flats.

Back 66

Inter/Supratidal sediments on LOW ENERGY TIDAL FLATS are from channels, levees, beach ridges, ponds, and intertidal flats.

Front 67

Trends associated with shorelines: moving towards the shore, what are the 4 trends?

Back 67

Moving towards the shore, grain size, sorting, and curren structure all increase; bioturbation decreases.

Front 68

Eolian Carbonates

Back 68

large bedforms
steep dips (30-34 degrees)
vf to fine sand sediments
early cementation

Front 69

Reef Classification: What are the 6 common shapes to reefs?

Back 69

Atoll, barrier,
Faro, fringing,
Patch, table

Front 70

Reef Classification: What are the 4 stratigraphic characters of reefs?

Back 70

bioherm
biostome
reef core
reef flank

Front 71

Reef Classification: What is the nature of reef builders?

Back 71

Frame-built: frame-builders & binders dom
Reef mounds: sediment contributors, bafflers & binders dom.
Mud mounds: precipitators & binders dom

Front 72

Reef dynamics and construction and primary frame

Back 72

primary framebuilders -> corals, algae, hydrozoans, stromatops -> bafflestones & framestones

Front 73

Reef dynamics and construction and secondary frame

Back 73

secondary framebuilders -> crustose coraline algae, stromatolites, microbes -> encrusters & bindstone
(shade-loving cavity dwellers also contribute)

Front 74

Reef dynamics and destruction causes

Back 74

physical (storms)
biological (bioeroders)

Front 75

Early cementation allows for....

Back 75

walls at the platform edge to be at 90 degrees or greater

Front 76

growth rate of reefs vs sea level rise
Reefs > SL
Reefs < SL
Reefs = SL

Back 76

Reefs > SL = prograding
Reefs < SL = drowning
Reefs = SL --> aggradation OR Backsteeping/Retreating

Front 77

Reefs Thru Time

Period and Major Skeletal Elements

Back 77

Tertiary - Corals
Cretaceous - Rudists
Devonian, Silurian, Orodvician - stromatoporids

Front 78

What are the 4 types of carbonate platforms?

Back 78

ramps
distally steepened ramp
rimmed shelf
isolated platform

Front 79

Cool water heterotrophs <-----> Tropical autotrophs

Back 79

ramp, dist stpd ramp <-----> rimmed shelf, iso platform

Front 80

South Florida is a __________
The Bahamas are _________

Back 80

South Floirda is a rimmed platform
Tha Bahamas are an isolated platform

Front 81

Isolated platforms have the greatest slope on the _______ side.

Back 81

Isolated platforms have the greatest slope on the windward side.

Front 82

What are some attributes of carbonate slopes?

Back 82

-they are dumping grounds for shallow water seds
-seds deposited by gravity flow processes
-rare setting for carbonate reservoir

Front 83

Slope models for ramp to rimmed shelf transition:
foreshore-shoreface model

Back 83

most gentle slope

Front 84

Slope models for ramp to rimmed shelf transition: Gullied slope model

Back 84

slightly thicker with a few mounds on top

Front 85

Slope models for ramp to rimmed shelf transition: Buildup-turbidite model

Back 85

thicker with mounds incorporated on inner layers

Front 86

Slope models for ramp to rimmed shelf transition: Rim-Debris flow model

Back 86

thickest, steepest, lots of cementation

Front 87

What are the 7 major types of sediment gravity flows?

Back 87

debris flow, fluidized flow, grain flow, rockfall, slide translational, slide rotational, turbidity current flow

Front 88

Slope elements and position, distance from platform margin (closest to furthest)

Back 88

rock falls, grain flows, debris flows, slump deposits, turbidites & hemipelagic mud, pelagic mud

Front 89

What is the dolomite problem?

Back 89

Dolomite is extremely common in ancient carbonates and rare in modern systems

Front 90

Where are most modern dolomites?

Back 90

between 30 degrees notrth & south latitude; The Alps in Northern Italy and the Guadalupe Mtns

Front 91

The dolomite unit cell is ____ than calcite. Therefore, this is a ________.

Back 91

The dolomite unit cell is smaller than calcite. Therefore, this is a volume reduction.

Front 92

What are the replacement textures of dolomites?

Back 92

fabric destructive, partial preservation, and mimetic

Front 93

What are the cement types associated with dolomites?

Back 93

simple rhombic, highly zoned, saddle rims

Front 94

What are the two primary models for dolomitization?

Back 94

sabkha/evaporation and seepage-reflux

Front 95

Controls on formation of evaporite deposits: first two salts to be precipitated...

Back 95

CaCO3 at 1.8X

CaSO4 at 3.8X

Front 96

Controls on formation of evaporite deposits: last two salts to be precipitated...

Back 96

NaCl at 10.6X

K Salts at 70X

Front 97

How are mud flat evaporites formed?

Back 97

Mud flat evaporites form by displacive evaporite growth in pre-existing sediments

Front 98

How are shallow water evaporites formed (these are the sabkhas / thin salts)?

Back 98

Shallow water evaporites form by the precipitation and/or sedimentation from shallow surface brine

Front 99

How are deep water evaporites formed (thick salts)?

Back 99

Deep water evaporites are precipitated in brines generally deeper than 20-40m

Front 100

What is the idealized salinity-increasing evaporative cycle?

Back 100

1) carbonate
2) gypsum
3) halite