Limestone (Packed)
Rock
Found in the Burren, and showing weathered out fossil packs.
This specimen shows the fossilised remains of ancient sea-lilies and corals. It also contains some small shell debris.
Limestone has a broad range of colour from grey/buff to cream/tan to bone white. There is even a pink limestone. They will all eventually turn grey when exposed to the elements over time.
Limestone is a calcareous rock made up of at least 50% of carbonate mostly in the form of calcite, argonite and dolomite. Limestone is regarded as a non-clastic sedimentary rock that can be formed from many geological processes. It is texturally, structurally and mineralogically extremely diverse, although a large proportion are biogenic (they contain fossil material).
The principal factor which unifies these carbonate rocks is their high reactivity to acids, some natural waters containing acid will cause erosion in these rocks.
Another characteristic of limestone is its softness, relative to other rocks such as granite. Biogenic limestone has a high degree of porosity. In cold climates, however, porous limestone can suffer rapid damage due to freeze-thaw cycling.
In the Burren one can see all the typical limestone landforms, underground rivers, swallow holes, glacial erratics, caves, clints and grykes and some turloughs (disappearing lakes). It is the youngest landscape in Europe and has suffered intense glaciation as recent as 15,000 years ago, when limestone was laid down under the sea in flat horizontal beds.
Clints are the blocks of limestone which constitute the flat pavements of the Burren and grykes are the open crevices which isolate the individual clints. The saucer-like pools collect debris and litter from the surrounding vegetation, and in turn set up acidic, rich black mould supporting some plants while simultaneously eroding the rock.
Ref: 2000.231-233
