The Mystery Thickens

Yesterday's beautiful weather enabled us to take some much better pictures of the site in Trevor Potts' Ardnamurchan Campsite, and these have drawn interest from both the local press and an eminent university's geology department.

The top picture shows the excavated area, with a very hard, granular limestone forming the base of the site and a limey shale above it - seen at the bottom of the face. These are of Jurassic age, about 130 million years ago, and dip gently away to the right. Above them is a much more massive ingeous intrusion, a cone sheet from the Ardnamurchan volcano, aged about 60 million years ago.

The mysterious structure is to the right. Click on the picture and it's circled in white.

This is a close-up of the western end the structure. Now that more of the rock has been cleared, it's obviously not an igneous dyke - but quite what it is has become even more of a mystery.

The white material seems to be calcium carbonate, of which limestone and modern reefs are formed. Its compact, upright structure suggest that it might be a 'reef knoll', perhaps an isolated reef which sat, like a mound, on a warm, shallow sea floor - the underlying limestone layer.

But the real excitement has come from finding objects like this within the structure. It's about 100mm across and has every appearance of being of organic origin - but it isn't like any fossil that The Diary has ever seen. It's closest resemblance is to a coral, but it doesn't appear to have some of the most important features of a coral. It may also be an ancient algal structure called a stromatolite - but we really don't know. There's a blog dedicated to these strange creatures here.

This is another view of the fossil, looking down from above. The biological structures seem to go round it, and to contain a darker, more massive infilling.

This picture shows the strange, tube-like structures and, to the left of the shadow, a couple of the 'golf balls'. We're finding more and more 'golf balls', not all of them perfectly spherical, some resembling button mushrooms. The surfaces of some of these show what might again be markings of biological origin.

One geology professor who saw these pictures commented, "These things are very weird. I've never seen anything like them before."

Trevor Potts runs the Ardnamurchan Campsite, website here.