Download Paleozoic, Late Ordovician Period, 450 Million Years ago

Origin of Planet Earth
450
Paleozoic
LATE ORDOVICIAN PERIOD
450 MILLION YEARS AGO
MORE SCIENCE FACTS
Approximately 575m (1,886 feet) below this location are
beds of the Collingwood Formation.You can see these beds
at the surface in the Craigleith area near Collingwood. Some
of these bituminous shales are full of trilobite fragments.
Trilobites, distantly related to crabs, moulted many times
during their lifetime and isolated body parts are commonly
found. The largest trilobite shows body segments (centre)
with an attached tail (bottom) while the headshield (top) is
offset. The specimen is about 6 cm in length.
The Ordovician is the second period of the Paleozoic.
The Ordovician Period is named from rocks in North Wales
that are present in the tribal area of the Ordovices.
By Late Ordovician time gradual uplift of this part of North
America had reduced the ocean to shallow water bodies that
contained very few animals. The Appalachian Mountains were
starting to rise along what is now the eastern edge of North
America. Rivers were sweeping sediments into the basin that
covered this part of Ontario (image). These sediments
became the reddish coloured fine-grained rocks of the
Queenston Formation and are encountered at a depth of
220 to 362m (722 - 1,187 feet) below you.
Near Waterloo the Ordovician Queenston Shale outcrops as
the red-coloured unit seen below the grey cap-rock of the
Niagara Escarpment at Milton (above).
Because the beds dip gently westward from the escarpment
the Queenston Shale is present from about 220m (722 feet)
under your feet.
The Queenston Shale was deposited in the waters of a shallow
sea. The sediments came from mountains being uplifted in
eastern North America in an early stage of the development of
the Appalachian Mountains.
The GeoTime Trail
Project has been
brought to you by
the generosity of
Concept, text and illustrations: Dr. Alan V. Morgan