Kilkenny Marble
(not a "true marble", but a fossiliferous Carboniferous limestone)
Limestone
Limestones belong to the group of sedimentary rocks known as chemical sediments. They are formed in a marine environment from the precipitation of calcium carbonate, the calcium having been brought into the sea via the hydrological cycle. Fossil shells are often found in limestones, and show that biological activity is very important too. Where CO2 concentration is low, calcite can be precipitated directly without any biological help, e.g. Bath Stone, which is an oolitic rock. The spherical ooids are through to have been precipitated as concentric layers built up around particles rolling around the sea floor. Pure limestone can be made up completely of calcite, but if other material is being laid down as well, such as sand, then the limestone will be impure.
Carboniferous limestone
Black/Blue/Dark grey Kilkenny marble is a finely grained Carboniferous limestone
(Lower Carboniferous, Butlersgrove Formation) that can show fossils.
The most widely-distributed sedimentary rock is Carboniferous limestones, the main rock across much of the central lowlands. In most places the limestones are overlain by materials deposited during or after the last glaciation. In a few areas, however, the cover is thin or non-existent and a distinctive limestone landscape has developed.
This is a well-cemented rock of low porosity, and occurring in thick beds. As they have prominent vertical joints, they can be easily spilt into blocks for use as building stone. It crops out, for example, in the Peak District, Mendips and Yorkshire Dales. It contains most of the country’s potholes and natural cave systems. Mostly, Carboniferous limestone is either a fine calcite mud, precipitated from warm shallow seas, or a shelly limestone, formed by fragments of animals such as corals. It is a very tough rock, and is commonly used as roadstone, but can also be used for cement making because it is often quite pure, and as a source of calcium carbonate for the chemical industry. These rocks formed between 363 and 325 million years ago.
Characteristics
Carboniferous Limestone is a sedimentary rock made of calcium carbonate. It is generally light-grey in colour, and is hard. It was formed in warm, shallow tropical seas teeming with life. The rock is made up of the shells and hard parts of millions of sea creatures, some up to 30 cm in length, encased in carbonate mud. Fossil corals, brachiopods and crinoids are very much in evidence as components of Carboniferous Limestone; indeed the rock is full of fossils.
Photo: limestone carboniferous yorkshire
Carboniferous Limestone has horizontal layers (beds) with bedding planes, and vertical joints. These joints are weaknesses in the rock, which are exploited by agents of both denudation and weathering. They also lead to the most important characteristic of Carboniferous Limestone – its permeability.Water seeps through the joints in the limestone. This creates a landscape geologists call karst, which lacks surface drainage but which has all manner of characteristic surface and subsurface features. The Carboniferous Limestone has been folded and faulted by massive Earth movements which can be seen by the fact that the rocks are now above sea-level and no longer horizontal.
Life in the Early Carboniferous
During the Early Carboniferous the Mendip area was part of a broad, shallow, tropical sea that stretched westwards into Pembrokeshire, and across which thick successions of Carboniferous Limestone, now forming the Mendip hills, was being deposited. A rich variety of life inhabited this marine environment, particularly corals, brachiopods and crinoids, which are the most commonly occurring fossils.
Crinoids
Crinoids inhabited shallow water and grew in dense clusters, sometimes called 'crinoid gardens' because of their resemblance to plants. Long stems were anchored to the sea bed, and held aloft a globose, cup-like structure with radiating arms. The whole animal is formed of many individual plates that usually become scattered when the creature dies. The stem plates are common fossils and the main constituent of crinoidal limestone.
Corals
Like modern-day coral reefs, the abundant remains of fossil corals in the Carboniferous limestone suggest the former existance of warm, clear, shallow and well-lit tropical seas. Corals have a variety of branching and encrusting shapes that provide homes for other creatures and act as a baffle to trap sediment. Different kinds of fossil corals occur at different levels in the limestone, allowing geologists to distinguish between older and younger beds.
Brachiopods
Brachiopods have become all but extinct in modern seas and oceans, but in the geological past they flourished at the shallow margins of oceans, especially in the Carboniferous. At first they appear little different from familiar modern-day sea shells, but they are in fact quite distinct, with different shell and soft part anatomy. Many brachiopods lived openly on the sea bed, but some such as Lingula, occurring near the base of the Carboniferous Limestone, inhabited burrows. Two important groups of brachiopods in the Carboniferous are strongly radially ribbed forms, called spiriferids, and large, less strongly ribbed forms with relatively plano-convex valves, called 'productids'.
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To get to log this cache you will have to visit and answer the questions which are related to the coordinates given the earthcache.
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Questions
1. Answer the questions under by visiting the Coordinates.
A. At gz you find a Kilkenny Stone, in what environment is this type of stone formed? (Answer can be found at the cache page)
B. Fossils often appear in this type of stone. Do you see any, and what type do you find: Crinoids, Corals and/or Brachiopods? Explain what you see, and what type of fossil you have found, and why you know what type it is out from characteristics and form? (Answer can be found at GZ)
C. On the marker there are darker spots with drawings in it. Have a look at the darker spots, and the area outside off it. What can you say about the surface? (Answer can be found at GZ)
D. What is the color of the marker stone? (Answer can be found at GZ)
2. Take a photo of yourself, the group or your GPS when logging the cache.
Without revealing any answers!
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Fiddlewood Stone
Link from the opening ceremony.
Standing stone set vertically and carved with a poetic inscription spiralling from the top interspersed with two children's tree drawings and four line drawings of leaves.
The inscription and drawings evoke the leafy woodland setting while acknowledging intrusions such as broken glass. References to children suggest ideas of community involvement while detailed observation of flora and fauna give a sense of place and history (daffadown dillies is an old term for daffodils and bishy-barney a local term for ladybirds)
