Stratigraphy Flashcards
(16 cards)
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
How long is precession cycle?
Chronostratigraphy
23 Kyr
