20 April 2012

Friday folds: Cape Liptrap

Posted by Callan Bentley

I got this note via email last week.

Hi Callan,

First of all, congratulations to your blog. It is just great.

I would like to contribute to your “Friday fold” section. A few words about myself. I am born in Austria and did my BSc and MSc at the Montanuniversitaet Leoben. In September 2011 I started my PhD here at Monash University (Australia), focusing on 3D implicit modelling of folded deposits with a view  to identifying the structural controls.

The picture below beautifully shows fold accommodation faults in a syncline, which are secondary faults that accommodate strain during folding. I also attached an annotated version of this picture.

Annotated version (red shows faults; blue is the trace of bedding on the outcrop surface):

All pictures were taken during a fieldtrip to Cape Liptrap, Victoria (Australia), south-east of Melbourne near Walkerville. The folded rocks are Devonian turbidites, alternating layers of mudstone (dark) and sandstone (light color) of variable thickness. Axial planar foliation is well developed in the (less competent) mudstones. There is also parasitic S and Z folding visible in the mudstones. The outcrop is a superb 3D exposure of folding .. you can literally ride the fold hinge 😉

Furthermore, a lot of primary (sedimentary) structures can be observed in this area. Flute casts, load casts, graded bedding and cross bedding, which help us to define the younging direction. Oh, and I forgot to mention the beautiful slump folds… see the pictures below.

I hope you keep updating your blog like you do right now.



Thanks, Stefan, both for the kind words about the blog, and also for contributing these excellent images of excellent folds.