2 August 2019

Friday fold: kinks in gritty phyllite near Lawn, Newfoundland

Posted by Callan Bentley

So there I was, driving west on the southern Burin Peninsula, when we passed a roadside quarry, and a shimmery apparition caught my eye – low angle “X” shapes, gleaming in diamonds and criss-crosses in silver and dark gray, the colors shifting as the car carried me past.

Hit the brakes!

Back up, park, jump out with the camera.

The rocks were gleaming with the sheen of muscovite, but they also had gritty pebble-sized bits in them – a phyllitic diamictite? A meta-tuff? (The latter’s more likely on the Burin Peninsula, which is dominated by volcanic strata.)

Regardless, these suckers got kinked!

Kink bands are crisp folds that occur in highly mechanically layered rocks when they are compressed at some angle to that layering.

These boulders show nice conjugate pairs of kink band orientations. If they were in place, rather than piled up higgeldly piggledly, then a structural geologist would be able to work out the direction of maximum compressional stresses that acted on these rocks.