It finally happened! After 10 years of being denied access to one of the all time best fossil collecting spots in North America myself, and a few other lucky geologists were allowed into the quarry with unrestricted access for the day last Thursday! The last time I visited Colborne Quarry was before I had started my undergraduate. Shortly after that visit all collecting access to the quarry was suspended due to an incident with the gate and the potential liability of us wandering around a giant open pit all by ourselves. Fair enough. Since then I have wanted to get back in there, but opportunities have been few and far between. If you recall, the best fossil in my personal collection came out of Colborne: Bert and Ernie!
Let’s back up a bit though. Colborne Quarry is a massive open pit limestone quarry located in Colborne, Ontario.
The town of Colborne could actually fit quite comfortably in the quarry itself. Indeed, the quarry is 2 kilometeres long by 1.5 wide and is currently ~150m deep. It opened in the early 1950’s and is expected to produce limestone aggregate for another 120 years at which point it will be around 250m deep. The quarry lies in the middle Ordovician aged Cobourg formation and extends down into the Sherman Falls formation as well.
The reason that myself and several others from the university were interested in going was not only because of the fossils. We are all working on a project to store low and intermediate level radioactive waste in the Cobourg Formation 500km west of Colborne and this was a rare opportunity to look at the Cobourg in outcrop as opposed to core. I have seen lots of Cobourg formation in core samples, but it is a completly different story when you can see outcrop. It makes it possible to see lateral continuity of beds, hydrothermal fracture filling, vuggy porosity, faults and many other features that it is much harder to glean from the core. We were particularly interested in looking for fluid conducting features such as faults or porosity that it is easy to miss with a core section. We were also interested in looking for fossils as well.
Colborne is a very, very active quarry. They blast every day the weather permits, luckily not the day we were there, and when they are not blasting they are drilling blast holes all over the place. The limestone is then loaded from the crusher onto a ship that conveys the rock to Mississauga, Ontario where it gets turned into cement.
While we were in the quarry we also took advantage and did a bit of fossil collecting. I didn’t find anything that comes up to the Bert and Ernie standard, but I did pretty well.
So that pretty much does it for this trip. It was a great day and after all those years waiting to get back into the quarry it did not disappoint!