L2: The nature of the fossil record Flashcards
What is the first step to becoming a fossil?
Die and avoid destruction by biological or physical processes
What is taphonomy?
Branch of palaeontology that looks at the fossilisation process
What role does transportation play in the fossilisation process?
Need to be transported into an environment in which it can be buried.
What are some agents of transport?
Currents, waves, rivers, bioturbation, predation, hermit crabs
What can be inferred from a fossil assemblage?
If in their life habitat,, can be used to infer palaeoenvironmental conditions
What is sedimentation?
When sediments such as sand, silt and mud are deposited geographically in space and time, via wind, water or volcano etc.
What is an accommodation space?
A sediment trap, where sediment will be deposited
How does sedimentary rock form?
Formed by the deposition and accumulation of sediments. The weight of overlying sediments causes compaction, squeezing out all the liquid from between the particles. Cementation than occurs a salts crystallise out between the grains
What happens to a fossil if it becomes too deeply buried?
Will likely be destroyed due to metamorphosis at high temperatures and pressures
What is metamorphosis?
Change that takes place within a body of rock as a result of it being subjected to conditions that are different from those in which it formed e.g. temperature and pressure increases
What is diagenesis?
The physical and chemical changes occurring during the conversion of sediment to sedimentary rock.
Why is the fossil record incomplete?
Sediments only accumulate over a very small amount of earth surface at a given time
Only a tiny fraction of the organisms that ever lived are fossilised
Many fossils are subsequently destroyed
Only a tiny fraction of fossils will ever be seen
Why is the fossil record bias?
Certain organisms/parts are preferentially preserved
Certain environments preferentially preserve sediments and hence fossils
Older rocks are more likely to be damaged
Collector bias
How do bacteria leave a fossil record?
Usually preserved by lithification, where their organic matter is replaced by minerals, often bacterial sheaths will be preserved
What protists are commonly preserved?
Those that form endotherm/exoskeletons e.g. radiolaria, diatoms, coccoliths
Which structures in plants are commonly preserved?
Woody tissues such as lignin, the cuticle and spores, are very hard to breakdown
What fungi would be preserved?
Spores and hyphae
Which animals are likely to be preserved?
Animals with recalcitrant ego and endo skeletons
In what environments do most fossils form?
Inland in flood plains, basins or on the continental shelf
What is the continental shelf?
Area of shallow seabed around the continent, where most life in the sea lives
What are turbidity currents?
a rapid, downhill flow of water caused by increased density due to high amounts of sediment
What is uplift?
Vertical elevation of land mass, oceanic crust may be put on land
What happens to the fossil record when the sea level rises?
More continental shelf, so is higher rate of preservation. This occurs in green house world when there aren no ice sheets.
What occurred in Central America during the Permian?
Inland sea flooding, an epicentral sea, due to extremely high sea levels
