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QUANTITATIVE BIOSTRATIGRAPHY, Slides of Quantitative Techniques

Advantages of the new tools in frontier stratigraphy are: Standardisation during computer input of the fossil record and execution of (semi-) objective stratigraphic methods gives access to all data and interpretations. Data sets and results are easy to communicate and rapidly updated with new information. Integration of all fossil and also physical (e.g. isotope, well-log) events in one stratigraphic solution increases resolution and practical use.

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Pre 2010

Available from 08/28/2023

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QUANTITATIVE BIOSTRATIGRAPHY
Advantages of the new tools in frontier stratigraphy are:
1. Standardisation during computer input of the fossil record and execution of (semi-)
objective stratigraphic methods gives access to all data and interpretations.
2. Data sets and results are easy to communicate and rapidly updated with new
information.
3. Integration of all fossil and also physical (e.g. isotope, well-log) events in one
stratigraphic solution increases resolution and practical use.
4. Methods and results (zonation + correlation) are more objective than hand-made
solutions.
5. Zones, events and their correlations may have error bars attached.
6. Such analysis of uncertainty in the fossil event record, and in quantitative zonation
improves insight in true stratigraphic resolution and reliability of event correlation.
7. Interpolation of missing event positions in sections increases detail in correlations
between sections.
8. Unlike subjective stratigraphy, the new methods provides more than one possible
solution to the data, depending on run conditions (multiple working hypothesis).
9. Sequence stratigraphic levels or trends may be detected and visualized.
10. The new methods handle large and complex data sets, and calculate reliable
stratigraphic solutions fast
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QUANTITATIVE BIOSTRATIGRAPHY

Advantages of the new tools in frontier stratigraphy are:

  1. Standardisation during computer input of the fossil record and execution of (semi-) objective stratigraphic methods gives access to all data and interpretations.
  2. Data sets and results are easy to communicate and rapidly updated with new information.
  3. Integration of all fossil and also physical (e.g. isotope, well-log) events in one stratigraphic solution increases resolution and practical use.
  4. Methods and results (zonation + correlation) are more objective than hand-made solutions.
  5. Zones, events and their correlations may have error bars attached.
  6. Such analysis of uncertainty in the fossil event record, and in quantitative zonation improves insight in true stratigraphic resolution and reliability of event correlation.
  7. Interpolation of missing event positions in sections increases detail in correlations between sections.
  8. Unlike subjective stratigraphy, the new methods provides more than one possible solution to the data, depending on run conditions (multiple working hypothesis).
  9. Sequence stratigraphic levels or trends may be detected and visualized.
  10. The new methods handle large and complex data sets, and calculate reliable stratigraphic solutions fast

BASIC CONCEPT

QUANTITATIVE BIOSTRTIGRAPHY

  • If a taxon is relatively abundant in a stratigraphic section (e.g.,

Heterosphaeridium difficile in Display 1, diagram 1a), it may be

possible to define different types of biostratigraphic events for it.

  • In practical use, most type of biostratigraphic zones are defined on

presence and absence of taxa rather than abundance data.

  • Normally a taxon occurs in relatively few samples from along an

exploratory well. Events distributions are illustrated in Display 1,

(diagram 1B). It illustrates that microfossils and nannofossils observed

in exploratory wells (and the stratigraphic events derived from them:

mainly last occurrences in these applications) have exceedingly skew

frequency distributions. In general, the great majority of taxa are

observed in one or a few wells only. Very few taxa if any occur in all

or nearly all stratigraphic sections studied for a basin.

  • First appearance datum (FAD)
    • In principle – time of evolutionary origin of the taxon
    • In practice – time it became abundant and widespread enough to be likely to be preserved and discovered as a fossil
  • Last appearance datum (LAD)
    • In principle – time of extinction of a taxon
    • In practice – time when it fell to numbers too low to be preserved and discovered as a fossil and populations did not recover

BASIC CONCEPT

QUANTITATIVE BIOSTRTIGRAPHY

local versus regional ranges Diagram 2A: Theoretical example showing distributions in space and time of seven different taxa with true chronological succession

Biostratigraphic Zones

• Stratigraphic intervals defined by the

occurrence of one or more particular fossil

taxa – species – sometimes genera

• Usually named for one or two taxa used to

recognize that interval

Types of Zones

• Assemblage zones – based on co-occurrences of an

assemblage of taxa – may be defined on the basis

of one or two first or last occurrences

• Abundance or acme zones - defined by peaks in

abundance of one or more taxa

– strongly controlled by environmental conditions

– not likely to be reliable outside of one region, except

possibly for plankton responding to global

oceanographic changes

BASIC CONCEPT

QUANTITATIVE BIOSTRTIGRAPHY

  • Zonations are essential tools for biostratigraphic correlation.
  • Conceptually, the average interval zone is similar to the Oppel zone of

diagram 3A except that the deviations from the average for the

observed first or last occurrences of the taxa (if these occur in a well)

are much greater. By means of averaging techniques it may be possible

to estimate the intervals between stratigraphic events along a relative

time scale. Then the stratigraphically average highest and lowest

occurrences of the taxa considered are assigned positions along a

distance scale (diagram 3C). Both the origin and the unit of distance on

this scale are arbitrary. The same type of information can be

represented as a dendrogram (diagram 3C). Clusters in the dendrogram

can be regarded as biozones and are often very useful for regional

(basin-wide) correlations

BASIC CONCEPT

QUANTITATIVE BIOSTRTIGRAPHY

RASC zonations are based on average stratigraphic events. The average interval zone between the exists of taxa A and B begins before the highest occurrence of B in section 3, and ends before the highest occurrence of A in section 2.

A
B

BASIC CONCEPT

QUANTITATIVE BIOSTRTIGRAPHY

  • Estimation of the highest and lowest occurrence of taxa top base observed range true range t t
T
T

Relationship between observed range extending from t1 to t2 and true range from T1 to T2. Strauss and Sadler (1989) assumed that the probability of finding a fossil is constant across its true range. If species is less abundant at its time of appearance, it becomes more difficult to estimate the true range even if facies and sedimentation rate remained constant. Using unbiased point estimator and the upper range extention to 95% confidence interval

BASIC CONCEPT

QUANTITATIVE BIOSTRTIGRAPHY Estimation

of the highest and lowest occurrence of taxa

  • Highest occurrence can be obtained using unbiased point estimator of

Straus and Sadler (1989) based on dirichlet distribution. The upper

range extention is 95% of confidence interval.

100m 50m Actual find Observed local range Upper range extention to unbiased point estimator Upper range extention to 95% confidence interval

3874 Lowest occurrence based on calculation

BASIC CONCEPT

QUANTITATIVE BIOSTRTIGRAPHY Estimation

of the highest and lowest occurrence of taxa

  • Signor and Lipps (1982)
    • Taxa begin to disappear from the fossil record before mass extinctions

actually take place.

diversity time