Sedimentology and Paleontology Lecture 19: Biogenic sedimentary structures (Trace Fossils)

Question 1

List various animal activity that can become trace fossils

Answer 1

Trackways(Footprints)
Trails (E.g. Snail footprints)
Burrows
Bite marks & Coprolites
Animal dung

Question 2

Define a trace fossil

Answer 2

Trace fossils = biogenic sedimentary structures

Result from behavioural interactions between organisms and substrates

Classified on the basis of their morphology into ichnogenera and ichnospecies

Question 3

Describe key concepts of trace fossils

Answer 3

Different organisms performing the same behaviour can leave behind the same type of trace

The same organism performing different
behaviours can leave behind different traces

Preserved in situ

Activities of soft bodied organisms

Question 4

Define Ichnofacies

Answer 4

Ichnofacies = certain associations of trace fossils recurrent across space and time - reflect environmental conditions

Meaning that similar trace fossils can be made by different organisms throughout time, and they reflect the environmental conditions - as these two similars have adopted a way of life receptive to the environmental conditions

Question 5

Describe how marine ichnofacies vary

Answer 5

Marine Ichnofacies vary with depth

Shallow to Deep
Skolithos Cruziana Zoophycos Nereites

Question 6

Describe the Skolithos assemblage

Answer 6

The Skolithos assemblage is found in shallow marine environments - Sandy shore (Littoral zone)

These trace fossils have a U or horseshoe shape and are vertical burrows into the sediment.

Some are pellet lined

Question 7

Describe the environements of the fossils in the Skolithos assemblage

Answer 7

High energy foreshore, shoreface and
channel environments

Question 8

Describe the Cruziana assemblage

Answer 8

The Cruziana Assemblage is still relatively shallow (slightly deeper than the Skolithos), at the Subliteral zone.

This trace fossil is mostly surface tracks and trails as well as complex networks of burrows; horizontal, vertical and branching.

Question 9

Describe the environments of the fossils of the Cruziana assemblage

Answer 9

Offshore shelf environments

Question 10

Describe the Zoophycos assemblage

Answer 10

Deeper than the Skolithos and Cruziana. It is fairly deep - in the Bathyal zone.

These trace fossils have limited variety, some range from ammonoid looking like shape fossils to Horn like trace fossils made up of little circles.

Question 11

Describe the environment of the fossils of the Zoophycos assemblage

Answer 11

Low oxygen bathyal slope environments

Question 12

Describe the Nereites assemblage

Answer 12

In the Abyssal zone, very deep in the ocean

Regular patterns seen on bed surface only. These trace fossils range from squiggly lines which don’t cross over one another to honeycomb like patterns

Question 13

Describe the environment of fossils of the Nereites assemblage

Answer 13

Abyssal plain environments

Question 14

What are the two types of ichnofacies

Answer 14

Oceanic/Submarine trace fossils
Continental trace fossils

Question 15

Describe the Ichnogenus Scoyenia

Answer 15

Subaqueous-subaerial continental environments

Some looks similar almost to a snake or centipede

Some specimens have parallel lines of shapes

Overall almost all look like a trail of some kind

Horizontal to vertical, curved, slender, ropelike burrows.
That in some samples appear to widen and narrow along their long axis.
Unbranched and commonly crossing each other. May have a ropey or wrinkled texture.

Question 16

Describe the Ichnogenus Mermia

Answer 16

The trace fossils in this genus look like mostly like squiggly lines. Some are straighter lines crossing over each other

Subaqueous lacustrine (relating to or associated with lakes) environments.
Meaning likely found in lakes `

Question 17

Describe the Ichnogenus Coprinisphaera

Answer 17

Consists of trace fossils of bees, wasps, ants, beetles, termites and other undeter- mined insects

The trace fossils in this ichnogenus seem to be mostly burrows

Question 18

Describe the Ichnogenus Entradichnus

Answer 18

Found in Desert environment

Wide variety of trace fossils; ranges from trackways, trails and burrows

Trackways look almost look like hands or paws

Question 19

Describe the substrate controlled ichnofacies called Trypanites

Answer 19

These trace fossils are found in hard ground substrates.

Looks like almost all burrows

Question 20

Describe the substrate controlled ichnofacies called Teredolites

Answer 20

Teredolites are trace fossils found in wood substrates

Almost all burrows

E.g. worms that burrow into wood.

Question 21

Describe the substrate controlled ichnofacies Glossifungites

Answer 21

Mainly burrows
Found in firm ground substrates