Clonony Marble

Notes:

A pale brown, sienna-coloured limestone composed of micrite and a low percentage of fossil material (wackestone). It contains many fossils including visible crinoids and some cephalopod molluscs. The latter, related to the modern-day Nautilus swam in surface waters and controlled buoyancy through gas-filled chambers in its shell which can be seen in some examples in this stone. In thin section various other small fossil organisms can be identified: bryozoans, crinoid ossicles, ostracods, small brachiopods, and molluscs. Original cavities in the lime muds are infilled with white sparry calcite and thin clay seams as well as veins infilled with grey calcite and also a series of wavy lines called stylolites. These formed as the rock became subjected to pressure such that some of the lime began to dissolve along these horizons. Stylolites are not strictly linear but have a three-dimensional shape which is highly convoluted and as such they do not reduce the cohesive strength of the limestone