19 June 2015
Friday fold: subglacial drag fold (Pleistocene) in Cretaceous sediments, Alberta
Posted by Callan Bentley
Howard Allen, a retired petroleum geologist from Calgary, and longtime reader of this blog, contributed this week’s Friday fold:
Subglacial drag fold (Pleistocene) in Upper Cretaceous Horseshoe Canyon Fm. bedrock (sandstone, shale).
The locality is SE of Drumheller, AB at UTM 12U 394247 5692469 (WGS84).
Did you hear that right? Yes, you did: This is Cretaceous aged sedimentary rock, folded by a Pleistocene glacier, tens of millions of years after it was deposited. And a massive tongue of ice did it!
Here’s another perspective on the same fold, looking roughly along (regional) strike to north, the direction from which the Laurentide ice sheet moved:
A very happy Friday to you!
Beautiful images there!
It seems that the rock was under the simple shearing when forming. That is, passive folding might be the major fold mechanism here.
In this case, it could belong to Class 2 folds (Similar folds).
(brief ideas from the photos)