EGU Blogs

Back in Colborne Quarry!

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.

A close up view of the whole quarry in air photo form. (Photo: Matt Herod)

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.

The outlet of the crusher. (Photo: Matt Herod)

Each truck load drops 100 tonnes into the crusher. They have two trucks running 10 hours/day. (Photo: Matt Herod)

The ship coming into port for loading. It runs 24/7 and makes one trip to the quarry every 20 hours. The rock HAS to be ready for loading each 20 hour cycle every day of the week. (Photo: Matt Herod)

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.

We did most of the collecting on piles of un-collected rock. We had to move fast since this material was headed to the crusher in a few short hours. (Photo: Matt Herod)

A giant trilobite!! A few key pieces are missing, but it shows how big they can get. (Photo: Matt Herod)

A really nice complete trilobite. Only a tiny bit of the head is missing. (Photo: Matt Herod)

The best find of my day!! A complete and very large specimen of an unusual species of trilobite. It doesn’t look compete, but the rest of it is under the rock and so it will require some careful cleaning to bring out its full glory. (Photo: Matt Herod)

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!



Matt Herod is a Ph.D Candidate in the Department of Earth Sciences at the University of Ottawa in Ontario, Canada. His research focuses on the geochemistry of iodine and the radioactive isotope iodine-129. His work involves characterizing the cycle and sources of 129I in the Canadian Arctic and applying this to long term radioactive waste disposal and the effect of Fukushima fallout. His project includes field work and lab work at the André E. Lalonde 3MV AMS Laboratory. Matt blogs about any topic in geology that interests him, and attempts to make these topics understandable to everyone. Tweets as @GeoHerod.


  1. Nice! It appears to be some kind of cheirurid. I have never found a complete specimen from the Mid.-Late Ord of Kentucky.

    • I think you are absolutely right. They are unusual for sure. I have found a few complete specimens in Southern Ontario over the years but they are mostly 1-5cm max. This guys is at least double that so it could be a great find once cleaned…I really hope the head and tail are under there!!!

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