Geomagnetic Polarity
Time Scale (GPTS)
• Berggren et al., 1985
• Berggren et al., 1995
• Gradstein et al., 2004
ODP Site 1207,
northwest Pacific
• Drilling Objectives:
– P/E Boundary
– K/T Boundary
– Aptian/Albian
1
ODP Site 1207
ODP Site 1207,
northwest Pacific
Age/Depth
2
Correlation of strata by fossils
BIOSTRATIGRAPHY
Correlation of rock strata based on fossil
characteristics
–
oldest method of determining relative age
• Application
–
–
Marine & Terrestrial Strata
Relative vs. Absolute time
• Basis - Evolution
1. Species appear & disappear (geologically instant)
2. Rapid distribution
3
Controlling factors on the Distribution of
Organisms in the Rock Record
1. Evolution
Controlling factors on the Distribution of
Organisms in the Rock Record
2. Paleoecology
– Environmental restrictions/preferences
– facies controlled organisms - restricted to
certain sedimentary environment
e.g. molluscs - restricted to near shore environments
Transgressive sequence
(deepening upward)
time 3
time 2
time 1
4
Controlling factors on the Distribution of
Organisms in the Rock Record
3. Preservation (Taphonomy)
– present, but not preserved (e.g. Burgess Shale)
Biostratigraphic Zonations
Biozone - basic unit defined or characterized by presence of
fossil taxa that permit it to be distinguished from
adjacent rocks
• Stratigraphic Nomenclature (applies to most fossil
groups)
– range- stratigraphic distribution in a given section
– first appearance datum (FAD) - immigration or
evolution
– last appearance datum (LAD) - extinction or
emigration
– range zone - all of the strata containing a specific
species or group of species.
– Taxon range zone-FAD to LAD of a single species
5
Biozones
•
formally named, defined, and assigned type
sections
Fossil ranges (species A-D)
Biozones
Teilzone: local FAD & LAD of a taxon
Fossil ranges (species A-D)
6
Biozones
Taxon Range Zone: Global FAD & LAD of that taxon
Requires inference - Global correlation of horizons bearing the
fossil taxon
Fossil ranges (species A-D)
Biozones
Concurrent Range Zone: Intersection of the ranges of two
or more taxa (globally defined)
A
B
Interval Zone: two successive FADs or two successive
LADs (globally defined)
B
A
A
B
7
Biozones
Assemblage Zone: Characterized by 3 or more taxa in
natural assemblage
–
fuzzy boundaries, as FADs and LADs aren't simultaneous.
Fossil ranges (species A-D)
Biozones
Lineage Zone: defined by the evolutionary first appearance
of successive taxa in a lineage (related)
C
B
A
Abundance (Acme) zone: concentration of a
particular taxa
8
Additional Zonation Schemes
Hypothetical Stratigraphic Section
Composite Ranges (locally)
• How are the absolute ages of these zones determined?
9
Potential Pitfalls in Biostratigraphy
1.
2.
3.
4.
5.
6.
Reworking and Hiatuses
• bioturbation: various models , downslope reworking, currents
• artificial range truncation of FAD or LAD.
Preservation (Taphonomy)
• Dissolution, oxidation, etc.
Bioprovinciality
• Restricted range
Migration (Emigration)
• environment changes
• Evolve
Sampling and/or counting biases
• Artificial Range truncation
• Last occurrence precedes extinction
1. Low temporal sample resolution
2. alternating good and bad preservation,
Taxonomic inconsistencies (misidentification)
10
Major Marine Macrofossils
Graptolites - plankton
Conodonts - nekton
• Paleozoic
• Widespread
• High rates of evolution
Dicranograptus nicholsoni
Planktonic or epiplanktonic graptolite
11
Index Fossils:
abundant fossils that are characteristic of a formation
or a period of time
• characteristics of ideal index fossils:
– distinctive
– widespread
– abundant
– independent of facies
– evolve rapidly
– short ranging
Plankton
12
Estimated Mean Species Duration (Myr)
calcareous nannofossils (coccoliths)
• phytoplankton
– autotrophic, Unicellular marine algae
– Phylum-protists
Coccolithophore Calcidiscus leptoporus
13
calcareous nannofossils (coccoliths)
• Shell - CaCO3
– Shields-elliptical to circular (1 to 15 µm)
– envelop the cell, form a sphere-post mortem disintegration usually
breaks down the shell into individual shields
Coccolithus pelagicus
temperate
Emiliania Huxleyi
calcareous nannofossils (coccoliths)
• Advantages
1. High rates of evolution
short stratigraphic ranges
2. Morphologically more simple (easier to identify)
3. cosmopolitan species
rapid dispersal rates
not as diachronous
4. Abundant; reduced opportunity for sampling biases
5. Quick/simple method
Braarudosphaera bigelowi
14
Cruciplacolithus phylogenetic lineage
• Appear at the K/T
boundary
– C. Danicus
• dominant genus Paleocene & Eocene
Discoaster Evolution
D. saipanensis
D. multiradiatus
• Appear in mid-Paleocene
• Evolve toward less robust bodies and
fewer rays
15
Eocene calcareous nannofossils
Biogeography
Relative Abundances as a
function of latitude &
depth in the N. Atlantic
Climate Zones
• Sub-arctic/Sub-antarctic
(2-6°C)
– E. huxleyi
• Transitional (6-12°C)
– R. clavigera
• Subtropical (14-28°C)
– U. irregularis
• Tropical (>28°C)
– G. oceanica
– E. huxleyi (eq. upwelling)
16
17
Planktonic Foraminifera
• Zooplankton, single cell Protozoa
• Calcite Shells
Morozovella
Velascoensis
Late Paleocene
Globorotalia opima continuosa (Miocene)
Globigerina yeguaensis (Oligocene)
18
Dinoflagellates
• Mainly planktonic
• Photoautrophic/Heterotrop
hic
• Virtually all aquatic
environments, but mainly
marine
• Organic cysts
• Abundant in coastal and
high-latitude
environments/ sediments
Enneadocysta partridgei
• Eocene antarctic endemic
LO near E/O boundary
19
Dinocyst Ecology
Yes
No
Integrating biozones from a
variety of depositional
environments?
• Sections interfinger
– Boundaries between facies
• Coastal Regions
• Correlation Methods independent
of facies
– Magnetostratigraphy
– Chemostratigraphy?
20
Biostratigraphy in Continental Sediments
Challenges
• Organisms tend to be highly provincial
– Plants
– Vertebrates
– Invertebrates (confined to water)
• Fossil abundances extremely low
– Dilution
– Preservation
North America Land Mammal Age (NALMA)
Orohippus (Eocene)
Hyracotherium (Eocene)
21
Graphic Correlation
1.
Standard Reference Section
–
–
2.
3.
4.
Thickest
Most complete
Fossil Ranges vs. depth
Select second section
Fossil Ranges (SRS) vs. depth
Graphic Correlation
6. Cross plot the sections
–
7.
Common FO/LO
Line of Correlation (LOC)
–
Regression (best fit)
Are all the correlation
points reliable?
22
Graphic Correlation
• Determine relative
Sedimentation rates
• distance = rate x
time
d=rxt
r = d/t
23