Hi Everyone,
Sorry this post is a bit late. Things have been crazy the last few days in the lab. I am trying to get enough done in the next few weeks to submit an abstract to a conference and I still have quite a long way to go. The 19th photo of week was taken by me at the Hogan Sand Pit just north of Ottawa near Cantley, Quebec. It is a pretty interesting sedimentological feature called a “flame structure”. This feature forms underwater when the overlying pressure of the sediment above a lower unit, in the case it is sand over clay, forces the underlying unit upward. A good analogy for this is if you think about the plumes of sediment that fly up when you step in mud underwater. The downward pressure of your bodyweight forces the sediment to fly and curl upward. Obviously, this is an instantaneous process, whereas the one pictured occurred at a slower pace. However, the mechanism that creates the “flame” is the same.
In this case the sediments pictured are glacial outwash sediments deposited as the Laurentide Ice Sheet melted 10,000 years ago. It is interesting to note that the presence of a flame structure indicates that the sediments were deposited underwater in a pro-glacial lake setting as opposed to a sub-aerial outwash plain like a sandur. Furthermore, the interbedded nature of the sand and clay could used to interpret the sort of depositional conditions in front of the glacier.
Cheers,
Matt
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