Stromatolite
from
Thunder
Bay.
Wayne
DeBrusk
of
Shuniah
Twp.
near
Thunder
Bay
has
donated
a
wonderful
example
of
stromatolitic
limestone,
originally
from
the
Eaglehead
Lake
area
north
of
Thunder
Bay.
This
one
was
found
in
a
gravel
pit.
Strom
as
Wayne
calls
it
is
installed
in
our
rock
garden.
Close
up
of
the
stromatolites
showing
the
cone-shaped
growth
lines
of
the
cyanobacteria
which
gradually
built
the
rock
in
a
quiet
part
of
the
sea
away
from
wave
action.
As
found
in
Shark
Bay,
Australia
today.
Strom's
story
This
boulder
was
found
in
an
aggregate
quarry
in
MacGregor
Township,
north
of
Thunder
Bay,
Ontario.
It
was
glacially
transported
to
the
location
where
it
was
found
during
the
last
Ice
Age,
possibly
originating
from
a
site,
near
Eaglehead
Lake,
70
km
north
of
Thunder
Bay.
It
was
donated
to
the
Peter
Russell
Rock
Garden
by
Wayne,
Chris
and
Cori
Debrusk,
in
memory
of
Sybil
Debrusk.
The
laminated
form
results
from
the
presence
of
stromatolites,
which
are
structures
produced
by
the
trapping,
binding,
and/or
precipitation
of
sediment
by
the
activity
and
growth
of
micro
organisms
in
water.
These
fossilized,
microscopic
organisms,
similar
to
modern
blue-green
algae,
flourished
in
shallow,
warm
water
near
the
shoreline.
They
trapped
sediment
on
their
sticky
surfaces
as
they
grew,
building
layer
upon
layer.
Lime-rich
sedimentary
rocks,
sandstones,
siltstones
and
mudstones
of
the
Sibley
Group
(yellow
on
the
geology
map)
formed
in
a
large
lake
that
extended
from
the
Armstrong
area
to
present-day
Lake
Superior
in
Precambrian
times,
about
1.5
billion
years
ago.
Stromatolites
occur
mostly
in
the
Middlebrun
Bay
Member
of
the
Sibley
Group.
These
rocks
were
metamorphosed
by
the
intrusion
of
hot
magma
about
1.1
billion
years
ago.
Geological
map
of
the
area
northwest
of
Lake
Superior.
From
the
Ontario
Ministry
of
Northern
Development,
Mines
and
Forestry.
Stromatolites
are
found
in
similar
environments
today,
such
as
Shark
Bay,
Western
Australia
(see
photograph).
Stromatolites
in
Shark
Bay,
Western
Australia.
Courtesy
of
Viajejet.com
Artist’s
conception
of
what
Lake
Superior
might
have
looked
like
billions
of
years
ago.
Note
the
knob-like
stromatolites
along
the
shore.
From
agatelady.
This
particular
stromatolite,
belonging
to
the
genus
Conophyton,
displays
a
characteristic
conical
pattern
in
its
laminae.
Imagine
these
stromatolites
growing,
points
upward,
like
a
stack
of
upside-down
ice-cream
cones.
Organisms
like
these,
often
found
preserved
in
rocks
up
to
three
billion
years
old
in
northwestern
Ontario,
were
the
starting
point
for
biologic
evolution
and
were
instrumental
in
producing
an
oxygenated
atmosphere
through
photosynthesis.
Donated
by
Wayne,
Chris
(alumnus,
B.
Sc.,
B.
A.
1994)
and
Cori
Debrusk,
in
loving
memory
of
my
wife
and
our
mother,
Sybil
Debrusk.
A
“rare
earth”
woman,
loved
and
cherished
by
so
many.
