Friday, May 2, 2014

Geo 730: May 2, Day 488: Argillite Prow

Resembling the prow of a grounded boat, these blocks of argillite were probably once all one larger boulder. Through processes both natural (weathering and frost wedging, for example) and human, they've been split into a number of smaller slabs. This is somewhat metamorphosed, I think; it's more indurated than shale by a long shot, but the foliation and cleavage is not as well developed as I would expect in slate.

In the mid-distance on the left, you can see the wine grapes foreshadowed in Wednesday's post.

Photo unmodified. July 10, 2012. FlashEarth location.


Callan Bentley said...

Is this Belt argillite, a boulder rafted (or tumbled) there in the Missoula outwash floods?

Lockwood said...

It is, or described as likely so. It was certainly ice rafted into place- it's on top of a ~150-foot high hill. Don't know if you've read previous posts on this spot, but they started this past Monday. The sign in that post is a decent description.