If it’s real, then it’s spectacular – Accretionary Wedge 42 Entry
January 21, 2012 in Accretionary Wedge
This Accretionary Wedge entry if from Bob Chesson who said “The conglomerate (meta sediment) is called green marinacci (sp?)which I believe is from South Africa. Not sure if the name is a ‘trade’ name or the actual formation name. but is definitely cool.” Obviously, this looks like a conglomerate, but I’m a little suspicious that it may be an engineered stone made up of loose cobbles, artificially cemented together, but I would need to take a closer look. What do the rest of you think? Either way, it’s a beautiful stone. Thanks for sending it in, Bob. For the rest of you, make sure to get your entries in by the end of the month to be entered to win the special geologic prize pack.
The clasts look like from consistent high-grade meta/plutonic provenance, but that might be true for loose modern gravel and cobbles just as well. What I’d like to see in much more detail is the matrix, which I’d be willing to bet no one would bother trying to make convincing to close geological inspection. As it is, I’m not willing to call for a way toward or away for either.
But whichever it actually is, it is exceptionally pretty, and I don’t think I’ve ever seen a decorative stone like it. Nice!
It wouldn’t surprise me at all if this was glacial diamictite (tillite) from the Proterozoic Gowganda Formation in Ontario, or some similar unit. I’ve seen rocks like this in the field north of Elliot Lake, Ontario.
Bingo! I knew I’d seen similar rock before, which is why I was careful to use “decorative” in final sentence.
It is not an engineered stone but a meta sediment. Matrix is quartzite with minor clays, sometimes choloritized.