25 March 2013

Incipient boudinage in overturned Edinburg Formation

Posted by Callan Bentley

Boudinage is such a fun structure. Here’s an example from the roadcut adjacent to the quarry featured so heavily last week.

The thick limestone stratum in the center of the photo has been stretched left-to-right. It exhibits pinch-and-swell structure, the first stage of boudinage. Small extensional fractures began to form in the boudin necks, accommodating the strain. Muddier strata above and below flowed into these boudin necks.

This is in the overturned limb of the fold, by the way: these strata have been tectonically inverted (flipped up-side-down).