The photo of that Gowganda Tillite is a bit misleading when it comes to examining the matrix because there are drops and spatters of tree sap and other debris making it look more diverse than it really is. The matrix is almost entirely clay. We know this in part from polished specimens we have in our labs. The granitic stones really are then surrounded by mud which is marine in origin. The granitic stones still fit the definition of dropstones you described, even if the mud shows no stratification (at least on a boulder scale).

Thanks for asking. I hope you continue to visit our blog.

Regarding your second photo, I wonder if “dropstone” is the right term in this case? My understanding of “dropstone” (at least of the glacial variety) is that it’s a stone, carried on or embedded in a raft of ice, that then drops (hence the name) into finer, stratified muds/silts/sands on a lake or sea bottom when the ice melts.

From what I can see in the photo, you’ve got a round granite pebble amid an extremely poorly sorted and apparently unstratified matrix: green mud, sand, granules and pebbles all mixed together willy-nilly–typical of glacial till (as you say, “Gowganda Tillite”). How about “erratic” or “till clast”?

Regards,
–Howard (Calgary, Canada)