Geology
Black Cliff
Sugar Loaf
The Sugarloaf is a cone shaped mountain made up of sediments
deposited in a lake that was formed as the ice sheet melted around 280 million
years ago, it is also said to be Hallett Cove’s most famous feature. The
bottom of the Sugarloaf is made up of red sand which is covered by
white sand. The white sand is then topped off with a layer of brown
clay that was deposited a few million years ago. The Sugarloaf is got its name because it looks like a mountain of hard refined sugar. It
is a cone shape because of the erosion caused by rain and wind over the
last few thousand years. The layers tell us that around 280 million
years ago southern Australia was covered by an ice cap but melted 10
million years after that.
Chatter Marks
The Hallett Cove chatter marks are an interesting sight and very popular with geologists because of the
history they hold. The marks strongly support Professor
Ralph Tate's theory that a South Australia was once covered in an ice sheet during the ice age.
Chatter marks are formed when a glacier moves across rocks, dragging stones along with it, forming the distinctive scarthes. The Hallett Cove
chatter marks are estimated to have been created around 280 million
years ago.
Slickensides
Slickenside is formed when a fold appears in the rock. Folding happens when friction between layers of sedimentary rock cause heat. This heat changes the sedimentary rock into metamorphic rock that has clear and distinctive parallel lines showing the direction of minor or major shifts between two layers of rock.
Layers of Rock
Hallett Cove Conservation Park is full of visible layers of rock that show just how old the site is. Many of the Hallett Cove attractions such as the Sugarloaf and the Amphitheater are made up of sedimentary rock. Sedimentary rock is made when sediments are deposited into water, where they then sink to the bottom and become compressed overtime. This cycle creates layers of sediments that can be observed in the Hallett Cove Conservation Park. The layers of the rock can also show the evidence of tectonic plates moving from the folds and faults in the rock. The sedimentary rocks in the Hallett Cove Conservation Park are said to be over 600 million years old.
Fossils
It was said that approximately three million years ago, the Hallett Cove Conservation Park was immersed in water. Throughout its short time underwater, a small layer of aquatic fossils were deposited on the sea floor. This is evident because of the shell imprints that are visible, but on the other hand there are not an abundant quantity of fossils because the Hallett Cove area was only underwater for a short period.