Stratigraphy Flashcards
3 Most often used stratigraphies used in Paleobiology
- Lithostratigraphy (rock framework)
- Biostratigraphy (ranges of fossils)
- Chronostratigraphy (time dimension)
What is an unconformity?
Lithostratigraphy
Successions of rocks divided by gaps. A break in time in an otherwise continuous succession.
What is a Zone fossil?
Biostratigraphy
Fossils that characterize a particular time period or biozone
First Appearance Datum (FAD)
Biostratigraphy
First appearance of a fossil in a rock section
Last Appearance Datum (LAD)
Biostratigraphy
Last appearance of a fossil in a rock section
Signor-Lipps effect
Biostratigraphy
Stratigraphic ranges are always shorter than the true range of species - you never find the last fossil of a species.
Applied on a larger scale, the Signor-Lipps effect can make abrupt mass extinctions appear gradual.
4 things that make a good zone fossil
Biostratigraphy
- Rapidly evolving
- Widespread across different facies and biogeographic provinces
- Easy to identify
- Relatively common
2 methods of quantative biostratigraphy
Biostratigraphy
- RASC - Ranking and Scaling
- CONOP - Constrainted optimisation
Golden Spike
Chronostratigraphy
Marks the base of a chronostratigraphic interval
GSSP
Chronostratigraphy
Global Standard Section and Point
Agreement where the golden spike will be
What is a transgressive event?
Sea floods the land
What is a regressive event
When the sea withdraws from the land
Milankovitch Cycle
Chronostratigraphy
- Eccentricity - Variation in Earths orbit from Circle to Elliptical
- Obliquity - Wobble of Earths axis
- Precession - change in direction of Earths axis relative to the sun
How long is Eccentricity cycle?
Chronostratigraphy
100kyr
How long is obliquity cycle?
Chronostratigraphy
41 kyr
