Whitemud Ravine Mineral
Springs
The Edmonton Landscape is a direct
result of the last great glaciation(18000) years ago . Our area was
covered by ice over 1Km thick which melted and formed an enormous
lake(Glacial Lake Edmonton) Most of our topography and strata are
due to this huge event. Edmonton generally consists of a very thick
layer of glacial till(unsorted glacial deposits, mostly clays and
sands) You have to get fairly deep to find preglacial
features.
Our river valley and splendid ravines cut deep into the past and
provide a window into subterrainian Edmonton. At the bottom of our
river valley lies a prehistoric formation that consists of
impermeable clay rich bedrock called the Edmonton Group. The rock
in the Edmonton Group is from the age of the dinosaurs(mesozic
65-250million years ago), this is where you would have to be to
find dinosaurs in Edmonton. Before the last glaciation, our area
contained an ancient river and it deposited many gravel beds
throughout the area. These gravel beds lie directly above the
Edmonton Group. The next layer up in our chronological sandwich is
the layer of Glacial deposits. The next layer above that is the
topsoils and vegetation that we are very familiar with.
This earthcache is going to introduce you the Edmonton
Group(formation), the Preglacial Gravel Beds, and the massive
glacial till deposits. Whitemud ravine cuts a very deep narrow
crevice and provides a spectacular setting to view these
features.
You will find parking @ N 53 30.140 W 113 33.635. Please proceed on
the small bridge by the washrooms and take the path uphill. You are
walking mostly on river floodplain deposits so the Edmonton Group
is not readily visible, however you can feel smooth rock
occasionally under the path, yes that is the Edmonton Formation.
There is an excellent outcrop of the Edmonton Group @ N53 30.067
W113 33.552. Please look at the surrounding exposed rock. Note
their colors and textures. The color you are seeing in the rock is
distinctive, as the Edmonton Group contains the mineral
bentonite.
You will next proceed to the Preglacial Gravel Bed. Continue up the
trail to N53 30.039 W113 33.501. You are now standing at the
Preglacial Gravel Bed juncture. The discontinuity is very apparent
and you will notice that you are standing on a flat grassy area
with several springs appearing all along the discontinuity. The
gravel bed is permeable to water and is carrying ground water along
the ancient riverbed. The whitemud ravine has crosscut the ancient
riverbed. This spring has a very high mineral content, which is
quickly being precipitated out right in front of you. The most
common spring mineral precipitates that are found in this ravine
are tufa(hard white calcium carbonate deposits), soft red limonite(
a mixture of iron oxides) and black wad( a manganese oxide). You
will not see a gravel outcrop due to the abundant grasses growing
in the mircoclimate created by the spring. Before you move on to
visit the Glacial deposits above, make a note of your current
elevation on your GPSr.
Proceed up the hill to approximately N53 30.056 W113 33.492. Here
you standing at the foot of a very steep exposed bank of glacial
deposits. This is glacial till, it is a mixture of clay and sand
with some assorted rocks. Please note the color of the till. Due to
the high concentration of clay, this formation is also quite
impermeable to water as well. If you look at the top of the
formation directly under the topsoil you will notice a slightly
different color of clays, this was deposited by Glacial Lake
Edmonton.
In order to get credit for this Earthcache you will need to email
me the answers to these questions.
1) Describe the color and texture of the Edmonton Group outcrop
found at N53 30.067 W113 33.552.
2) Describe the color of the mineral that is being precipitated out
of the mineral spring, What mineral is it?
3) Estimate the thickness of the glacial till by using your
elevation at N53 30.039 W113 33.501
4) Post a photo of you and your group and your Gps at one of the
three waypoints.