The more pics I look at, the more I think that they're either silver or red maple, but I just don't know.
Edit: Okay I did some digging around in the snow, and I did manage to find dead leaves on the ground in the vicinity. There are both red and silver maple leaves on the ground in abundance and a handful of sugar maple ones too, but I can't say for sure which trees they came from or if they simply blew in.