Carbonate Environments

Question 1

For Dunham’s grainstones, would you find them below or above wave base?

Answer 1

Above. there is no mud

Question 2

For Dunham’s mudtsones, are they high or low energy?

Answer 2

low

Question 3

What would cause a buildup of carbonate material?

Answer 3

• need a lot of organisms with carbonate skeletal structures
• low siliclastic input, need a flatter terrain so sediment doesn’t come down from the continent

Question 4

What is a sabkha?

Answer 4

A transition zone where the environment goes form wet to dry. It is an area of high evaporation, so get a lot of evaporites.

Question 5

What type of environment do you usually find carbonates?

Answer 5

Tropical

Question 6

What is a shoal?

Answer 6

Ribbed, ramp like underwater sandbar that is slightly off shore. Between a shoal and the shore is a lagoon.

Question 7

Describe Irwin’s Z Zone

Answer 7

The area of water closest to the shore - includes lagoons, tidal flats and sabkha. Low energy. You get algal laminations, stromolites, burrowing and desiccation cracks. You also get fecal pellets (bc there isn’t much aggitation disturbing the seds), intraclasts, skeletal sands and mud.

Question 8

T/F: In order to make carbonates, you need very deep & turbid water.

Answer 8

F, you need clean and shallow water.

Question 9

Describe Irwin’s Y Zone

Answer 9

The area where you see a shoal, high energy area. Tidal megaripples, barrier islands and reefs. The structures you would get are: cross-bedding, cross-lamination and channeling. You would also see oolitic and skeletal sands, and reefs.

Question 10

Describe Irwin’s X Zone

Answer 10

You would throw your ex here.
Offshore, low energy. You would get lamination in this area. Mostly mud lithology.

Question 11

Where, in Irwin’s sedimentation model, would you get wackestones, packstones, grainstones and mudstones?

Answer 11

X Zone - mudtsones
Y Zone - wackestone & packstone at edges of shoal. grainstone at highest point of shoal
Z Zone - wackestone

Question 12

Where does wave base begin in Irwin’s sedimentation model?

Answer 12

X zone

Question 13

Study Irwin’s XYZ vertical sequence

Answer 13

Question 14

Study this carbonate shelf diagram showing where you can find diff lithologies and grain types on carbonate shelfs

Answer 14

Question 15

What are grape stones and where do you usually find them?

Answer 15

Grapestones are an aggregate of carbonate grains. You usually find them below wave base. Commonly found in shallow, low-energy environments like subtidal areas, where carbonate grains are subjected to less intense wave action.

Question 16

What are ooids? Where are they found in carbonate shelf environments?

Answer 16

carbonate grains that consist of concentric layers of calcium carbonate precipitated around a central nucleus. found in the slope of a carbonate shelf

Question 17

If you see ooilitic shoals, what does that tell you about precipitation rate and amount of agitation happening?

Answer 17

It is high precipitation and high agitation

Question 18

What are the components that go into making lime mud on lagoon floors?

Answer 18

pellets, break up of larger carbonate grains, bio-erosion, death of algea, erosion of tidal flats

Question 19

How does sea level change affect carbonate shelves?

Answer 19

In a high sea level time the sediment is deposited because the floor is below wave base, but in low sea level there is an erosion and lithification of the floor

Question 20

What is a reef?

Answer 20

A structure on the floor created by living organisms. The kind of organisms that contribute to a reef change over time.

Question 21

Study this diagram about reef sections

Answer 21

Question 22

What is the highest point on a reef called?

Answer 22

The reef crest. Shallow corals encrusting and hemispherical corals, high energy

Question 23

This slide is on the exam - study

Answer 23

Question 24

Review Dunham classification

Answer 24

Question 25

Reef forms: When you get a delicate, branching reef form, what does that say about wave energy and sedimentation?

Answer 25

Low and high

Question 26

Reef forms: When you get a thin delicate, platelike reef form, what does that say about wave energy and sedimentation?

Answer 26

Low energy low sed

Question 27

Reef forms: When you get a globular, bulbous, columnar reef form, what does that say about wave energy and sedimentation?

Answer 27

moderate wave, high sed

Question 28

Reef forms: When you get a robust, dendroid branching reef form, what does that say about wave energy and sedimentation?

Answer 28

mod-high wave energy, moderate sed

Question 29

Reef forms: When you get a hemispherical, domal, irregular, massive reef form, what does that say about wave energy and sedimentation?

Answer 29

mod-high wave energy, low sed

Question 30

Reef forms: When you get am encrusting reef form, what does that say about wave energy and sedimentation?

Answer 30

intense wave, low sed

Question 31

Reef forms: When you get a tabular reef form, what does that say about wave energy and sedimentation?

Answer 31

moderate wave, low sed

Question 32

On a lagoon, what type of coral shape would you see?

Answer 32

branching coral

Question 33

On the fore-reef, what kind of coral shape would you expect to see?

Answer 33

foliaceous forms (the ones in class that had big palms).

Question 34

On the reefcrest, what shape corals would you expect to see?

Answer 34

Massive shape

Question 35

El Capitan is a reef system from what time zone?

Answer 35

Permian

Question 36

What is taphonomy?

Answer 36

How things are getting preserved. Involves weathering, whether the structure is whole or broken, where the preserved structure is found. Related to the environment

Question 37

study this taphonomy diagram

Answer 37

Question 38

What does “carbonate factory” refer to?

Answer 38

Carbonates constitute the predominant sediment in very limited environments. Carbonates are common only in clear, warm, shallow tropical to subtropical seas.

Question 39

What are carbonate ramps?

Answer 39

Shallow areas of the contentential shelf, usually low angle.

Question 40

What is a rimmed ramp?

Answer 40

A shoal. Sand or skeletal material that is offshore, like a coral reef. Breaks the waves before goes to the shore.

Question 41

Of the XYZ ones, which are most likely to have burrows?

Answer 41

Z zone

Question 42

Describe the back reef

Answer 42

high light, low energy, tidal, high turbidity, high sed. finger-cylindrical corals

Question 43

What area of the reef system is this description match: not affected by waves, little sunlight, adapted to low light conditions -- foliaceous forms

Answer 43

forereef