Core Samples

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Core Samples
Unlocking Puzzles of the Past
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What is a Sediment Core?

• A sediment core is a long piece of sediment
  collected from the bottom of a body of water.
• The core is analyzed to reveal evidence of
  organisms that lived during sediment formation.

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How is a Core Collected?
Pushing the empty tube into the mud
Tube containing sediment core is carried out of
the pond

• Researchers push an empty tube into the pond
  bottom and use suction to pull out a core of
  sediment

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How is a Core Collected?
Removing a core from the tube

• The sediment core is removed from the empty tube
  in one continuous piece

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How is a Core Collected?
Measuring and describing a core
Wrapping a core

• The sediment core is described, carefully wrapped
  up, and taken back to the lab for study

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What Can We Find In Cores?

• Plant macrofossils are preserved seeds, leaves or
  other plant segments useful in identifying
  plants.
• Plant microfossils are tiny pollen grains and
  spores that are also useful, but can only be
  identified with a very strong microscope.

Seed
Leaf fragment
Pollen grains
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What Can We Find In Cores?

• We also can find signs of human activity such as
  charcoal from fires or metal from industrial
  activities

Industrial particle
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Relative Dating
? Top of Core ? Older macrofossils are
found at deeper levels ? Bottom of Core
Since shallow layers settled later, macrofossils
found higher are younger than those found in
deeper levels.
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Relative Dating
Relative dating of fossils doesnt give
information about actual age of the fossils but
it does allow researchers to understand how the
ecological community changed over time.
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Relative Dating

• By identifying plant macrofossils throughout the
  core, its possible to tell which plants were
  present when each sediment layer was formed.

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Compression

• The correlation between fossil depth and age is
  difficult to determine due to several factors
  including compression.

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Compression
As sediment layers settle one atop another, top
layers create pressure on lower layers. The
excess weight presses the lower layers tightly
together.
Sediment compression is exaggerated when the core
is pressed into the tube to be withdrawn.
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Why study Miller Woods?

• The Miller Woods are home to 150 ponds that are
  the last remnants of a once extensive pond
  system.

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Why study Miller Woods?

• The ponds formed in rows as glaciers, and Lake
  Michigan, retreated to the North in a process of
  melting, stalling and melting 15,000 years ago.

Glaciers covered Michigan 20,000 years ago
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Why study Miller Woods?

• Henry Cowles, for which Cowles bog is named,
  reported upwards of 50 rows of ponds in the area
  in the early 1900s. Today only a few remain with
  the rest having been taken over by industry and
  housing.

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Why study Miller Woods?

• These ponds contain many unique groups of plants
  and animals that need to be protected.
• We need to understand about how and why the plant
  communities have changed so we can protect them
  for the future

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In this set of Activities

• You will collect data from a sediment core to
  better understand how relative dating is used to
  track ecological changes.
• Youll compare the species that lived there
  through time and explore a connection to these
  changes and the spread of human development.
• Finally you will collect a core from a local pond
  to appreciate the methods involved.