Muir Creek Fossils

"an ideal park in jeopardy"

According to Rick Hudson, “Notable fossil sites include the exposed seashore west of Muir Creek, where a 15 meter high siltstone cliff contains well-defined marine fossils in a variety of strata, and 3 km up Muir Creek where there are fossils in random boulders exposed in the riverbed.

During the Neogene Period, 20 million to 25 million years ago, there was northsouth faulting with east-west stretching and thinning of the crust along the western continental coastline of North America. The volcanic activity is associated with the uplift of the Rocky Mountains and the Coast Mountains. The Sooke Formation (early Neogene) is the youngest of the Tertiary sediments, called the Carmanah Group, that make up the south west coast of Vancouver Island. It overlays the older Hesquiat Formation which comprises several thousand meters in thickness of silty shales interspersed  with conglomerates and sandstones. The Hesquiat Formation accumulated in deeper waters, while the Sooke Formation formed in shallower seas and therefore contains many fossils.

The Carmanah Group sediments show as a very narrow strip along the south west edge of Vancouver Island, stretching from the Sooke Basin to Nootka Sound. Nowhere are they extensive, and seldom are they accessible. The Sooke Formation is, at most, a few hundred meters thick and comprises conglomerate and fine grained silts, with the fossilized remains of diverse inshore fauna including gastropods, bivalves, barnacles and also the fossil bones and teeth of marine mammals.

The remnants of three different extinct marine mammals have been identified in this youngest of the Island’s fossil bearing sediments: a partial skull of the primitive whale, Chonecetus; teeth of the desmostylian, Cornwallius; and a molar in a partial lower jaw that is similar to the jaw of the Kolponomos—a large, bearlike carnivore. The jaw was found near the mouth of Muir Creek. Desmostylians were a group of amphibious quadrupeds related to elephants and manatees.

Upstream about 3 km is the first showing of fossils and of sandstone with fossil shells. Beyond the remains of the old logging bridge, accessible from either side of the creek via old logging roads, there is fossilized and partially fossilized wood. This fossil material is usually encased in the conglomerate rock that is common in the upper reaches of Muir Creek. These conglomerates form dramatic, undercut cliffs and caves along the creek bed. The fossilized wood is estimated to be 60 million years old. Poorly preserved and carbonized remains of beech, hickory, laurel, magnolia, and oak are found along with the remains of spruce and willow.”