Aug. 18: Bedrock and Glacial History of the Kimberley Nature Park with Daryl Hanson, P.Eng

Sunday, August 18, 2024

Hike report by Connie Jones

Brad and I have seen many informative guided hikes being offered in the Kimberley Nature Park and we have often said, “We should do that.”

It never happened. Until now. We decided that geology would be the hike that finally got us to a meeting place at a specific day and a specific time. It was on the calendar.

Up bright and early, we headed to the Campground Trailhead of the Kimberley Nature Park where we met up with around 30 other learners who were attending the day’s event of exploring the park’s bedrock and glacial history. Our guide was Daryl Hansen, P.Eng. (non-practising).

Daryl was wired up with a speaker system that made listening to him a pleasure, especially with such a large group. We learned right away that there were two types of rocks that we would see in the Kimberley Nature Park: Moyie and Aldridge. Daryl assured us that those two names were all we had to remember.

Aldridge rock was formed by layers of sediment compressed over time and Moyie rock was formed by magma (igneous rock) intruding the Aldridge layers. Then, over a long geological history, both layers had been folded and faulted. We also learned that there was once another, younger layer of rock, called the Creston formation, that disappeared in this park area with the movement of glaciers.

Our first stop was a bank cut on the highway just before the turn for the Campground Trailhead parking area. There we observed layers of unconsolidated silt. We learned that this was a feature of this area due to the fact that the St. Mary's Valley was once a huge shallow lake.

Onto the trail we headed to an outcrop of bedrock that was identified as Moyie. It was primarily massive, fine grained, grey igneous rock that featured ‘salt and pepper’ colouring. We used a magnifying glass that Daryl passed around which was a revelation. We were seeing rocks in an entirely new perspective.

Next we were off to find a spot where Aldridge and Moyie rock interfaced. We left the trail and hiked across a small scree slope to a site where we could observe where the two types of rocks were in contact. In an attempt to turn us all into geologists, Daryl demonstrated how to measure the orientation of the contact (strike and dip).

“Strike and dip is a measurement convention used to describe the plane orientation or attitude of a planar geologic feature.” (from Wikipedia)

Lastly, we headed up the trail a bit further to another site where we would see an excellent exposure of the Aldridge Formation. Daryl used a sweet little rock hammer to break off a piece of Aldridge rock which clearly illustrated the layers formed from all those sediments a billion years ago.

We had to duck out at this point and headed back to the parking area.

Things I learned:

1. Both types of rocks in this area are around 1.5 billion years old. The Moyie rock was formed from magma pushing up into the Aldridge rock.

2. Geologists use both hands to explain things: on one hand such and such may have happened, but on the other hand, perhaps such and such happened!

3. Geologists believe that rocks can float and when they find numerous loose pieces of a particular type of rock in an area they call it ‘float’. It suggests that that particular type of rock is under all the soil and plant life.

4. A short botany detour with Dina: Dina called to our attention an interesting little plant growing beside the trail. It is called Woodland Pinedrops or Pterospora andromedea. It is a tall, reddish purple plant with little urn shaped flowers. It is a root parasite depending on its association with a mycorrhizal fungus. It produces very little chlorophyll so is not green and does not photosynthesize.

5. Finally, I find myself wanting to add a magnifying glass and rock hammer to my backpack.Measuring strike and dip is beyond me so I won’t need the fancy compass.

Thank you to Daryl for an informative hike and talk. Thank you also to Dina and Betty who worked to meet the varied needs of such a large group!