Exceptional Preservation

Question 1

What is a Fossil-Lagerstätten?

Answer 1

Areas of extraordinary fossil preservation

Question 2

What are the two types of Fossil-Lagerstätten?

Answer 2

1. Konzentrat-Lagerstätten
2. Exceptional preservation

Question 3

What is Konzentrat-Lagerstätten?

Answer 3

Where fossils occur in unusual concentrations

Question 4

Examples of Konzentrat-Lagersträtten

Answer 4

• Lake dries up quickly and kills all the fish - large quantity of fish preserved in a concentrated area.
• Mass kills / Bone beds etc

Question 5

What is exceptional preservation?

Answer 5

When preservation is of unusual quality.

Question 6

What are the types of exceptional preservation?

Answer 6

• Preservation of organims that are not usually preserved.
• Preservation of parts of organisms that are not usually preserved
• Organisms are preserved unusually articulated or in unusual configurations

Question 7

Preservation of organism that are not usually preserved examples

Answer 7

Jellyfish, embryos, soft bodied organisms etc

Question 8

Preservation of parts of organisms that are not usually preserved examples

Answer 8

• Soft tissue
• E.g. Ichthyosaur skin

Question 9

Examples of when organisms are preserved unusually articulated or in unusual configurations.

Answer 9

Entire Ichthyosaur skeleton with embryos.

Question 10

What permits exceptional preservation?

Answer 10

• Exclusion of scavengers and bioturbators (anoxia, rapid burial, elevated salinity)
• Unusual chemical environment

Question 11

Effects of unusual chemical environment

Answer 11

• Nodule formation
• Microbial mats - death mask

Question 12

What is nodule formation?

Answer 12

• Concentrations form around the fossil which protect it from future decay.
• organims is buried in sediment and water is excluded - high pressure.
• E.g. flint nodules in chalk cliffs

Question 13

What can nodules be made out of?

Exceptional preservation

Answer 13

• Silica, flint, iron pirate, calcium carbonate.

Question 14

What are microbial mats?

Answer 14

Mats of microbes that form over organims and mineralise it effectively

Question 15

Examples of conservation traps

Answer 15

• Amber.
• Ice: permafrost deposits. Doesn’t date back that far (ice age).
• Tar pits.
• Hot silicious springs (geezers).
• Tufa: calcium carbonate areas - stalactites & stalagmites.
• Ash falls: ash and hot gas collapse down in pyroclastic flows. Can get up to 1000 degrees C and travel 450 mph - everything in the way gets preserved.

Question 16

Tissues display a spectrum of decay from recalcitrant to labile, what are these?

Answer 16

• Biomineralised endo- or exoskeletons e.g. bones, chitin.
• Robust structural tissue e.g. arthropod cuticle, woody tissue.
• Decay prone e.g. muscles, eyes etc

Question 17

How are decay prone tissues preserved?

Answer 17

They are only preserved when they are rapidly replicated by authigenic minerals

E.g. an eye needs to be preserved in a day otherwise it’ll rot away

Question 18

How do authigenic minerals preserve decay prone tissues?

Answer 18

1. Precipitate around the tissue and replicate it by mould/cast.
2. Precipitate on and within the tissues (often filling or preserving actual cells)

Microbes often perfom a critical role as they mineralise themselves

Question 19

Examples of minerals that preserve

Answer 19

Apatite: phosphate mineral. Small minerals that preserve small structures (muscles fibres etc).
Clay minerals: Also preserve minute structures. Not sure how this is done. (cold glacial environments).

Question 20

Phosphate preservation

Answer 20

During the pre-cambrian there was a abundance of phosphate.
Many tiny organims / structures were preserved.
Phosphate can only perserve very small structures.

Question 21

How can fossil-largerstattens confuse/divert us?

Answer 21

• False biodiversity peaks
• Preferentially occur during certain periods of geological time (e.g. cambrian)
• Certain unusual envronments are over-presented

Question 22

As well as apatite (phosphate) and clay minerals exceptional preservation may result from:-

Answer 22

• Iron pyrite (‘fools gold’)
• Other metal sulphides
• Silica (e.g. hot springs, nodule/concretion formation (flint), wood permineralisation) lignin has affinity for silica.
• Calcite (coal balls and other nodules/concretions) peat swamps

Question 23

Examples of some Fossil-Lagerstatten: Messel

Answer 23

• Cenozoic: Germany
• Volcanic erruption that caused a collpase of the surrounding environment.
• Big deep lake forms, bottom layers are anoxic, anything that falls down gets preserved as there is nothing to eat / decay it.
• Occational carbon monoxide clouds released into the environment which means anything surrounding / flying etc will die and fall into the lake to be preserved.

Question 24

Examples of Fossil-Lagerstatten: Hunsruck Slate

Answer 24

• Devonian: Germany.
• Shallow sea with stratified water column.
• Black mud containing anoxic bacteria.

Question 25

The Jehol biota (Cretaceous: China)

Dinosaur case study - exceptional preservation

Answer 25

• Series of lakes that dammed up due to volcanic activity
• Ash and water reacted to form weird chemical environments
• Unusual things like feathers preserved
• Ash is very fine grain so very fine intricate preservation
• Colour preservation in insects
• Lots of fish preserved
• Some cases where behaviours can be assumes due to how they are preserved (e.g. example of brooding with 2 adults and 2 juveniles)

Question 26

The Jehol biota (Cretaceous: China). What do we know about dinosaur colouration from these fossils?

Answer 26

• The Melanosomes in the feathers are the same as today
• Using a scanning electron microscope we can see what colours the feathers were.