Geology 105 - Paleontology
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Biostratigraphy

Reading: Chapter 2

We only need p. 23-40.

Background

Terms:

faunal succession - in undisturbed sedimentary rocks, the fossils always occur in the same order
fossil assemblage - collection of fossils found together
biostratigraphic zone - the vertical range of rock containing a specific fossil or set of fossils; the basic unit of biostratigraphy
stage - a vertical range of rock encompassing a specific set of zones
index fossil - organism used to define the boundaries of a zone
resolution - degree to which time intervals can be discriminated. The shorter the duration of the zone, the higher the resolution

 

Key Concepts and Questions:

1. What is the difference between the units defined in each of these kinds of stratigraphy? What are the uniots and how are they defined? Which units represent true time correlation?

Type of stratigraphy What are the units? How are they defined? Are they true time units? Why or why not?

 

Lithostratigraphy

 

     

 

Biostratigraphy

 

     

 

Chronostratigraphy

 

     

 

Sequence stratigraphy

 

     

 

Cyclostratigraphy

 

     

 

Magnetostratigraphy

 

     

 

1. How are biostratigraphic units defined?

For each kind of zone, define it, and illustrate what the ranges of the index fossils involved look like (see fig. 2.2).

Type of Zone
Definition
Ranges of index fossils

 

total (taxon) range zone

 

 

concurrent range zone

 

 

interval zone (we'll do this one in class)

 

 

consecutive-range (lineage) zone

 

 

assemblage zone

 

 

acme (abundance) zone

 

   

2. What makes a good index fossil?

In class we will indentify the characteristics of a good index fossil. In your reading, note any characteristics you run across:

 

 

 

 

 

 

3. What factors affect the effectiveness of a biostratigraphic zonation?

How do each of these factors affect the utility/accuracy of a biostratigraphic scheme (we will do this in class)?

Evolution:

 

Facies dependence:

 

Emigration:

 

Preservation:

 

Erosion/Hiatus:

 

Extinctions:

 

Reworking:

 

 

Assessment

1. Biostratigraphic units

You should be able to:

2. Index fossils

You should be able to:

3. Factors affecting zonation

You should be able to: