GeoSphere

Archives / 2013 / March

Geology Photo of the Week #25

The photo for this week is something a bit different. It is a piece from my personal collection that was self collected. Ok, full disclosure, my dad actually found it, but I was over on another rock pile in the quarry and finding jack at the time…so it is self collected….I did help extract it after he found it. I should also mention that they were repaired and enhanced by a professional to make them really “pop” out of the rock. However, no parts were added. They were found as complete specimens.

I don’t want to steal any paleontological thunder from Jon, but I have a fair amount of experience in paleo, particularly invertebrate paleo. In fact, the part of southern Ontario that I grew up in is stuffed with Ordovician fossils such as the trilobites pictured below. These particular trilobites, known to my family and others as “Bert and Ernie”, can be classified as Isotelus gigas, which is a common species in the region. However, complete trilobites of this size are exceptionally rare and to find them as a pair is simply ridiculous. Bert and Ernie were found in Colborne Quarry, a limestone aggregate quarry, famed among local collectors for its fantastic fossils. I used to go  to the quarry on a regular basis and found all sorts of great stuff over the years from complete crinoids to 1.5m cephalopods. Unfortunately  the company that owns the quarry has closed it to collecting and access is no longer possible. However, there are still lots of other places in the area where it is possible to collect in the same rocks. Stay-tuned for more personal collection highlights in the future. I have nice cephalopod that is hiding an unusual secret…

Cheers,

Matt

Geology Photo of the Week #24

The photo of the week is one that I took in November on my glacial sedimentology class trip to the Buckingham sand pit and at first glance it looks pretty boring. Nothing could be further from the truth though when you consider the implications of this lonely old block sitting al by itself in these sand beds. Also, my apologies for not including a scale. You’ll just have to take my word for it that this block was around 30 cm long and 15 cm high.

This block is called a dropstone. Dropstones are a glacial feature that occur when a stone that is incorporated into an iceberg or ice sheet falls out as it melts, the block settles through the water column and lands on the sediment beneath. The sediment continues to deposit and covers the stone. Because of the block the sand beds warp and deform around the shape of the stone as you can see in the picture. Dropstones are a smoking gun for indicating a marine or lacustrine environment since they can only be deposited in water. In this case the glacier, which was located nearby, was flowing into a large pro-glacial lake called glacial lake Champlain and deposited a huge amount of sand and clay in the Ottawa region as well as numerous dropstones.

A beautiful dropstone in the Buckingham sandpit, Buckingham, Quebec. (Photo: Matt Herod)