The Cambrian Period

					  The Cambrian Period
• Occurred 550-490 million years ago.
• Was the first period of the Paleozoic era.
• Adam Sedgwick named the period after
  the Roman name for Wales, Cambria. It
  was named for the site, in which shale and
  sandstone make up a two mile thick layer
  of land.
            Origin of the period
• Generally, the beginning of the Cambrian
  period is said to be marked by the
  appearance of the fossil Trichophycus

Some argue that the appearance of trilobites marks the
         beginning of the Cambrian period.
                    To the left we
                    see a map of
                    the modern
                    positions of
                    reference to
                    locations of
In the diagram to
the right, we see
the predicted
position of the
continents during
the period.
• This period is characterized by a huge burst of life in the
  form of great animal diversification, known as the
  Cambrian Explosion where in that time annelids,
  arthropods, mollusks, and many other phyla of animals
  appeared for the first time. Direct descendants of these
  animals are still present today, such as the jellyfish:
• Mostly consisted of desert and badlands,
  however, some green algae was thought to
• No land plants.
   Climate of the Cambrian Era
• Warm, wet, and mild weather.
• No significant ice formation, is
  considered a mild “spell” between two
  great ice ages of the Proterozoic age,
  and the late Ordovician age.
   The Ordovician Period
• Occurred 490-443 million years ago.
• Was directly after the Cambrian
• Was named by Charles Lapworth in
  1879 for the Celtic tribe, the
  Ordovices. They rebelled against the
  Roman domination.
 Origin of the Ordovician period
• The boundary between the Cambrian and
  Ordovician periods is marked by the appearance
  of planktic dictyonemid graptolites.
• The ending boundary of this period is designated
  as when black graptolite-bearing shale appear in
  the stratigraphy.
• These boundaries were determined by Lapworth
  using radiometric dating.
Above is the positioning of the
continents during this period.

               Another view is to the right,
               showing how North America
               and Europe were shaped.
• The Ordovician period is
  best characterized by the
  presence of diverse marine
• Animals included
  trilobites and many other
  species that, unfortunately,
  were extinct by the end of
  the Paleozoic era.
• Once again, green algae
  was one of the only forms
  of plant life, and was
  probably an evolving
  point for many other
  terrestrial plants.
• The first terrestrial plant,
  the liverwort appeared.
• The first fungi appeared in
  the late part of this period.
• For most of the period, the
  climate was warm and
  mild, especially around
  the seas. This explains
  why marine life thrived.
• The period ended abruptly
  with a brief ice age that
  consumed much of the
  polar regions glacially
  (300-500 ky).

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