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Posted Saturday, June 23, 2007
The National Stone Centre – Middleton by Wirksworth.
The History of Fossils
Popularised by television programmes like the Antiques Roadshow and Flog It, the collecting bug has bitten many of us and has become something of a cultural phenomenon in our affluent twenty-first century society.
`Antiques and Collectibles are big-business these days'
Antiques and Collectibles are big business these days, and not only in the entertainment industry!
Auction houses and sale rooms are springing up in every town and city, and spiralling prices reflect the increasing rarity value of finite antique commodities and have rocketed accordingly.
But did you know that in Derbyshire you can purchase ancient artefacts older than anything seen on the Antiques Roadshow for under a fiver?
As a rule, the older and rarer an object, then the greater it’s monetary value, but there are exceptions to every rule, and whilst you might pay a small fortune to obtain a thousand year old relic, or a couple of hundred pounds for a Georgian teapot, you can buy an artefact which is over 300 million years old for under a fiver in the Peak District!
`National Fossil Association'
It may surprise the majority to learn that fossil hunting and collecting comes relatively high on the list of `Hobbies and Pastimes’ indulged in by the UK population, and that in fact, there are in existence a number of organisations, including a National Fossil Association, which acts as a catalyst for thousands of budding paleontologists, geologists and students of natural history – as well as those who simply hunt and collect fossils.
So what exactly is a fossil and where is the best place to find them?
I discovered one or two old fossils amongst the editorial staff of the magazine I freelanced for, but they were neither interesting nor had any rarity value, and so I went to the National Stone Centre at Middleton-by-Wirksworth, a site designated as being of Special Scientific Interest and crammed with ancient tropical reefs.
There I met site paleontologist, Geoffrey Selby-Sly, who not only gave me a conducted tour of the unique 330 million year old exposed fossil reef, but explained what the fossils were and how they were formed.
For the uninitiated, fossils are the recognised remains, such as bones, shells or leaves, or other evidence, like tracks, burrows or impressions, of past life on earth, and scientists who study such fossils are known as paleontologists.
Fossils are a vital and valuable resource for scientists who study the Earth’s history, for they help determine the record of past events that are preserved in the rock, and in effect, the layers of rock are like pages in the Earth’s book of history.
Most of the rocks exposed at the surface of the Earth are sedimentary – which means they are formed from particles of older rocks that have been broken apart by the natural forces of wind and water. The gravel, sand and mud settles to the bottom in rivers, lakes and oceans and these sedimentary particles cover dead animals and plants in successive layers on the lake or ocean floor. Eventually with the passage of vast eons of time, the pressure on the accumulated particles at the bottom, accompanied by chemical reactions taking place, turns it into sedimentary rock, and the animal and plant remains trapped within become fossils.
Geoff explains: “Geologically most of Derbyshire is covered by limestone, with grits overlay, and with the coal measures towards Chesterfield in the eastern part of the county.
The fossils found in the limestone are mainly marine types, like bryozoa, crinoids, trilobites, brachiopods, goniatites, bivalve molluscs and coral - with plant debris found in the coal measures.
The most common early Carboniferous fossils found in the limestone reef at the National Stone Centre are crinoids and brachiopods, which together with other microscopic marine life, formed the bed of the shallow tropical inland lagoon here about 330 million years ago – they and and their shells became the carboniferous limestone dome of the White Peak.
Crinoids, also known as Sea-Lilies, looked like plants but were actually animals which attached themselves to the sea bed via a long stem. The animal lived in a swollen cup (calyx) at the top of the stalk, with long arms attached which looked like plant fronds. These arms were used to filter food from the water. The broken stems of the sea-lilies (crinoids) have the common name `Derbyshire Screw’ because when exposed in the rock, they look just like an embedded wood screw.
Brachiopods (Gigantoprocuctuc) – a shell fish which could attach itself to the sea bed by a stalk emerging from the rear of its shell, and bryozoa, a tiny colonial animal which resembles a small coral and grows in net like fronds, are numerous in the limestone and can be clearly seen in the exposed reef at the National Stone Centre.
The Story of Stone.
The Story of Stone, and specifically that of the limestone bedrock of Derbyshire is told graphically in a series of informative educational displays and illustrated guides at the NSC. Students and interested parties can see the fossils in situ and can actually take casts of certain fossils from the exposed limestone reefs. The displays explain the dating process of the rock and thus, the fossils that they contain, many examples of which can be purchased from the NSC `Rock Shop’ for under £5, along with a fabulous collection of gem stones and other fossils from all over the world. Sedimentary rocks are formed particle by particle and bed by bed over many millennia, thus any given bed studied must be older than any bed above it. This Law of Superposition, as paleontologists know it, is fundamental to the interpretation of Earths history and geological timescale. Layered rocks form when particles settle from water or air, and Steno’s Law of Original Horizontality states that most sediments, when originally formed, were laid down horizontally. This theory simplifies the quite complex problem of dating when considering that massive earth movements in promordial times created cracks, fissures, anticlines and different planes and levels, fracturing the horozontal beds of sedimentary rock and thrusting them upwards in a variety of directions.
In the late eighteenth and early nineteenth centuries, the English geologist and canal-building engineer William Smith, together with French paleontologists Georges Cuvier and Alexandre Brongniart discovered that rocks of the same age may contain the same fossils even when the rocks are fractured, separated and moved over long distances. The discovery that the solid land masses, previously thought to be in a fixed global position, were in fact in a constant flux and being moved by tectonic plates deep beneath the Earth’s surface, solved the mystery of why rocks of the same age and containing similar fossils were found hundreds and sometimes thousands of miles apart. For example, during the carboniferous period, the landmass that is now Britain was situated about five to ten degrees south of the Equator and enjoyed a warm tropical climate similar to that of the Pacific Islands today. Over a period of about a hundred million years, during what is known as the Permian and Triassic period, the British Isles gradually moved to it’s current position fifty degrees north of the Equator – and this explains why the fossils found in the Derbyshire limestone were once living creatures which thrived in what today seems a completely alien climate.
Because the fossils present in a rock exposure can be used to determine the ages of rocks very precisely, later scientists developed what is known as The Law of Fossil Succession, which has become vital to geologists who need to know the ages of the rocks they are studying.
Detailed studies of rocks from every part of the Earth revealed that some fossils which had a short, well known time-band of existence were prevalent almost everywhere. These are known as Index Fossils, and are vitally important for providing a fixed point in history on the vast geological time-scale during which the Earth was formed.
Fossils offer us a fascinating glimpse back into the past, in fact the earliest fossils provide our only knowledge of life on Earth in a time long before we ever set foot on the planet, and the unique Derbyshire fossils found in the reef at the NSC are some of the oldest in the world.
Fossils are the prized possessions of a growing number of avid collectors and come in all shapes and sizes; from bees in amber to dinosaur eggs, and from leaves and fish skeletons in coal seams, to ammonites and sea-lilies in limestone. Though the Derbyshire fossils which I unearthed in the magazine's editorial office were both uninteresting and thus worthless and decidedly uncollectible, the National Stone Centre had a wide range of fossils for sale on display from around the world – including a collection of dinosaur eggs - and a visit is highly recommended!