4 April 2014
We have a guest Friday fold today, from reader Ben Mackay-Scollay of the Monash University School of Geosciences in Melbourne:
Hey there Professor Bentley, been a fan of your blog for a while and I thought you might be able to use this for your Friday Fold series. It’s an upright fold at Bermagui in New South Wales, where I visited recently as part of my post-grad coursework for a structural geology course. The scale is around 3 metres across in this photo, and the fold is defined by the contrast in weathering between sandstone and mudstone layers. The mudstone layer at the top of the fold has formed into a chevron as a result of flexural slip, with the mudstone being forced into the low-pressure area.
The whole area has undergone something like 4-5 deformation events, but hasn’t ever been deep enough or hot enough to grow metamorphic minerals – this can make determining the relationships difficult. Also, it’s a national park, so we’re not allowed to take samples for thin sections either. It’s great to have something to debate back at camp every night though!
I check your blog most weeks, as do most of my fellow Honours students who are serious about their geological knowledge. It’s great to read about your work.
You’ll also note some bonus tafoni in there! Cool.
Thanks, Ben. Hopefully you’ll be sending us more great images like this in the future. I think your goal is to get up to “Ben Folds Five“!