Lecture 4 Flashcards
Facies
packages of sediments with a particular set of characteristics that formed in a particular depositional environment
Depositional system
an environment with a distinctive set of facies indicating different sedimentary environments
What is a biozone? How are they usually bounded and correlated? How are radiometric dates important?
Biozone: units of strata distinguished based on fossils, especially lowest and highest occurrences
Radiometric dating important to recognize diachronous biozones
What are the basic questions in determining the causes of biotic events? What is
meant by “correlation is not causation”, and how is that significant?
-Existence: How do we identify biotic events?
*Does the stratigraphic data support
a change in the ecosystem?
- Cause: How do we determine the cause of biotic events?
*Does the fossil record show the event at the same stratigraphic level as evidence of a potential cause?
-“Correlation is not causation” means that just because two variables are associated or occur together does not imply that one directly causes the other.
Explain how the incompleteness of the fossil record makes identifying biotic
events such as mass extinctions difficult (the Signor-Lipps effect)
because individual species may not be preserved uniformly across geological time.
How can confidence intervals be used to address the incompleteness of the fossil
record?
can be used to evaulate stratigraphic ranges, and therefore mass extinctions.
.How can unconformities be a problem?
can terminate the ranges of many taxa
How can the reworking of fossils cause problems?
may lead to inaccuracies in interpreting the age and evolutionary context of the fossils, as they may appear in a layer that does not correspond to their actual time of existence
What is a C13 excursion? What does it indicate, and why
rapid change in the isotopic composition of carbon-13 in geological records, often indicating significant shifts in the global carbon cycle.
