A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, hair, petrified wood, oil, coal, and DNA remnants.
Approximately 40% of the island of Ireland, and 50% of the Republic, is underlain by limestone. Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Most examples of fossils are found in limestone. The most common fossils in Irish limestone are Corals, Brachiopods & Crinoids.
1) CORALS are common in the limestone, and are often concentrated at specific levels in the limestone. Where present, the corals show that the sea was shallow enough to allow sunlight to penetrate the water to allow algae to photosynthesise. If the corals are cut in cross section, each branch appears as a small circle with white lines radiating out from the centre, like the spokes of a bicycle wheel. If the corals are cut in long section, they appear as long pencil-like features.
2) BRACHIOPODS or “lamp shells”, are very common fossils in the limestone. They are a type of shellfish with two valves and are still alive today. They live attached to the sea floor by a tough ligament-like stalk, and feed by filtering tiny particles of food (e.g. plankton) out of seawater. In cross section, the valves of the shell look like large white circles. In long section, the valves of the shell look like white semicircles. They are the most common type of fossils to be found in Irish limestone.
3) CRINOIDS are a relative of the starfish have a radial array of feathery arms on top of a vertical stem. They use their feathery arms to pick or pluck food particles from the seawater and place it in their mouth. After the animal dies, these soft tissues decay and the pieces of the skeleton fall apart. Where the crinoid pieces are cut in cross section, they appear as scattered white circular structures, about 2-10 mm wide. Where they are cut along their length, they appear as two parallel white lines with a jagged edge where they face each other.
When you arrive to GZ. Sit with the Beauty and answer following questions:
- What type of rock is limestone. .
- In GZ what fossils from the list above ARE NOT present?
- What is an average size (length and diameter) of fossils in GZ.
- Optional: Photos are welcome, but no spoilers please.
Looking forward to hear from you! :-)
Please feel free to log your find as soon as you have sent your answers. I will contact you if there are any issues.
HAPPY HUNTING!!!