I woke early one morning at El Questro and went for a walk up towards the escarpment of the Cockburn Ranges. I followed a narrow winding gully and came across this weird rock shelf.

It was formed in sedimentary layers, the underlying layer having the appearance of tidal ripples. Covering this was, what appears to be, a series of layers of flat mud turned to solid rock.

The really strange thing was the numerous fist sized oval depressions in this top layer.

The depressions are formed in rows and are evenly spaced.

They appear to have been formed when the mud layers were soft, but have hardened to dense, solid rock

This shot seems to indicate that the depressions were pressed into several layers of soft mud.

What caused the depressions?

The following day Jan, from our workshop group, came up with me to have a look. Jan has a background in science and a keen interest in geology – her son and his partner are both geologists. We scratched our heads and came up with various theories, but will wait til Jan gets some photos and samples back to her son for a more knowledgable analysis.