Biogenic Sedimentary Structures

Question 1

Trace fossil

Answer 1

Sedimentary structure formes due to the activity of organisms

Mostly macro organisms, but smallest scale effects of Bioturbation approach “grain size”

Question 2

What is Ichnology?

Answer 2

Study of traces and trace fossils

Question 3

Bioturbation

Answer 3

Reworking of sediment by organisms
Post-deposition disruption

The disturbance of sediments due to biological activity

Question 4

Burrows vs Boring

Answer 4

Burrows are tunnels in soft/loose substrate

Borings (bioerosion) are holes/ openings in HARD/firm substrate

Question 5

Track vs Trails

Answer 5

Tracks are series of discrete impressions in the sediment

Trail is one continuous disturbance in the sediment (slimes)

Question 6

Examples of Bioturbation

Answer 6

Boring
Burrows 
Track
Trail
Resting place
Feeding traces
Fecal pellets

Question 7

What is a great example (organism) of grazing trace

Answer 7

Trilobites

Question 8

What dictates the type of Bioturbation happening in an environment?

Answer 8

The type of organism and the substrate the organism is moving across

Question 9

What is a borer

Answer 9

A borer means that the organism can dig through hard substrate. A worm, mollusk, insect, or insect larva that bores into wood, other plant material, or rock. Some snails and mollusks have tongues reinforced with magnetite

Question 10

In terms of trace fossils, what kind of structures you can have?

Answer 10

Bioturbation structures (burrows,traces, trails, root penetration structures)

Biostratification structures (algal stromatolites, graded bedding of biogenic origin)

Bioerosion structures (borings scraping, biting)

Excrement ( coprolites, such as fecal pallets or fecal castings)

Question 11

What is the utility of trace fossils?

Answer 11

Important paleoecological indicators

Way up indicators!

Environmental interpretation/paleoclimate

Hydrocarbon recovery

Bioturbation can create porosity!! They alter what’s going on in the sedimentary layers altering the movement of fluids in the system

Question 12

How trace fossils are named (taxonomy)?

Answer 12

According to the Binomial nomenclature used for organisms!!

Name is given to the shape of the trace ( not the animal/plant/thing that formed it)!!

Relatively rare that ichnofossils can be assigned to a known body fossil

Question 13

What are ICHNOFACIES?

!!!

Answer 13

Is an assemblage of trace fossils that provide an indication of the environment conditions that their formative organism inhibit.

Or a group of ichnofossils associated with:

Bathymetry
Energy conditions
Sediment regimes

Question 14

Bathymetry

Answer 14

The measurement of depth of water in oceans, seas, or lakes

Question 15

What kind of information can ICHNOFACIES give us?

Answer 15

How deep it is

How energetic was the conditions of the system

What is the sediment regime

Question 16

What is ichnogenera?

Answer 16

Is the plural of ichnogenus, which is the name of the trace fossil

Question 17

What is the difference between ICHNOFACIES and ichnogenus?

Answer 17

Ichnofacies is an assemblage of ichnofossils associated with a particular environment (bathymetry, energy conditions, and sedimentation regimes)

Ichnogenus is the name of the ichnofossil. ( like Homo Sapiens).

Question 18

How important or how depth controls the type of ichnofossils with will find in the rock record?

With depth we have…

Answer 18

Less Biomass
Salinity (change with depth and also temperature)!
Light levels
Decreased O2 levels
Decreased Energy levels

But it is not a dead zone!

Question 19

Why there are not a lot of vertebrate tracks outside the shallow waters?
!!!

Answer 19

Because they tend to be swimming, so they don’t leave a lot of traces ( eg. fish)

Question 20

Why there are more burrows on relative shallow than in deep waters?

Answer 20

More Biomass! And because organisms can sit and wait for food

Question 21

Why there are more trails on deep/abyssal waters?

Answer 21

Because the organism has to find food. Scarce biomass on the deep abyssal zone

Question 22

What type of trace/ structure is created after the occurrence of mass movements/ turbidity flows and underwater landslides?

Answer 22

Scape structures

Question 23

Can you define a ICHNOFACIE baseon on trace?

Answer 23

NO. Tou have to look at different ichnofossils. E.g Zoophycus ichnogenus appears in 5 different ichnofacies. You name it based on the assemblage.

Question 24

What ICHNOFACIES represent? What tipe of information can you infer from them?
!!!

Answer 24

Different micro environments
Energy distribution 
Nutrient distribution 
Temperature 
Substrate expectations

Question 25

What is a facies?

Answer 25

A body of rock with a specific characteristic