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A free public resource dedicated to showcasing the prehistoric world. (C) 2008
Discovering Fossils is fully independent and works in partnership with JuniorGeo.

What is a fossil? How do they form?

Fossil Collecting Code

Fossil Collecting Code

 

Ammonite reconstruction (c) Discovering Fossils 2008

 

Introduction

 

Fossils are the remains of creatures which existed long ago.  Fossils range from thousands of years to many millions of years in age.  The earliest fossils date from around 600 million years ago, however recent reports suggest bacteria may have existed up to 3 billion years earlier.  To put this in context, the dinosaurs became extinct just 65 million years ago.

 

Not all former life was preserved as fossils, in fact the vast majority simply vanished without trace.  The most likely materials to survive fossilisation are the hard parts such as shells and objects which in life were constructed from resistant materials, such as Coral.  In order for softer materials to survive, the conditions must be extremely favourable.

 

Fossils come in a variety of sizes, from minute traces to large skeletons.  Trace fossils are clues to former life, they result from the activities or presence of creatures and plants.  Examples of these traces include footprints, burrows and root tunnels.  At the larger end of the scale, fossils also include bones, the largest of which belong to the dinosaurs, which existed between the Triassic and Cretaceous periods.

 

There are five different ways ways an organism can become fossilised:

 

Permineralization (Petrification) - This process involves the replacement of the original organic tissues with minerals from the surrounding rock, including silica, calcite or pyrite.

 

Unaltered preservation - This occurs when the organism is preserved in its original state and protected from the affects of permineralization.  Examples of this include insects which become trapped in tree sap, which later turns to amber.

 

Carbonization (Coalification) - This results from removal of all but the carbon elements.  Other elements such as hydrogen, oxygen, and nitrogen are removed.

 

Authigenic preservation - These fossils are the molds and casts of organisms which have dissolved or rotted away, leaving only a trace of their existence.

 

Recrystalization - This occurs where crystals form within the original structure, eventually replacing it and resulting in a crystallized copy.

 

The following diagrams illustrate the process of fossilisation, starting with the moment of death.  The example used is an ammonite, a shelled creature that lived in the seas around 150 million years ago.

 

 

Phase 1 - Death

 

 

Having died, the ammonite slowly sinks to the sea floor.  Scavengers feed on the fleshy body of the creature, and after only several weeks all that remains is the shell.

 

 

Phase 2 - Deposition

 

 

 

Several months after death the shell gradually becomes covered with silt and sand.  These layers continue to build, providing a shield around the shell and protecting it from damage.  Time continues to pass and more and more layers are deposited.  After a few hundred years the shell is several feet beneath the surface.

 

Time continues to pass, 1,000 years, 10,000 years and more...

 

 

Phase 3 - Permineralization*

 

 

Gradually the chemicals in the shell undergo a series of changes.  As the shell slowly decays, water infused with minerals passes through it, replacing the chemicals in the shell with rock-like minerals (Calcite, Iron or Silica).  This process is scientifically known as 'permineralization'.

 

 

Over millions of years the original shell is completely replaced by the minerals and what remains is a rock-like copy of the original shell.  The fossil has the same shape as the original object, but is actually rock.  This process also results in loss of original colour.

 

 

Phase 4 - Erosion

 

 

Over millions of years the movement of the earth plates results in the seabed being forced above the surface.  The result is a new landscape, within which the ammonite fossil remains buried.

 

Once above the surface the rock is subject to erosion.  In certain areas of the world such as Lyme Regis in Dorset, the rock is once again subject to the affects of the sea.  In these areas the rock is pounded by the sea, forming towering cliffs.  Other factors such as wind, rain, ice and the sun help contribute to the rate of erosion.

 

 

Phase 5 - Exposure

 

 

Having laid beneath the surface for 150 millions years the fossil is finally exposed.  This final stage may have resulted from a cliff collapse or the efforts of a paleontologist.

 

 

The fossil can then be removed from the ground, cleaned and examined.

   

  

Join us on a fossil hunt...

   

 

Portland dinosaur hunt - Sunday 11th May '08

 

Ever wished you could walk with dinosaurs? Now you can!

 

Discover the hidden secrets of Portland (Dorset), on a quarry tour with local expert and geologist Chris Pamplin, accompanied by the

Discovering Fossils & JuniorGeo team. Participants will see dinosaur trackways and foot prints, fossil trees, giant ammonites, prehistoric beaches and the Portland Sculpture park.

 

There will be some opportunities to collect fossils, but the main attraction of dinosaur footprints cannot be collected except with a camera!

 

This event requires driving between quarries. Full details will be provided to participants prior to the event.

 

Adults £10 / Children £5

  

Charmouth to Seatown fossil hunt - Sunday 22nd June '08

A classic Jurassic fossil hunt!

 

Join local expert and geologist Chris Pamplin to explore one of the most famous stretches of the Jurassic Coast, from Charmouth to Seatown, taking in Golden Cap.

 

This classic fossil locality is where Mary Anning found many of her remarkable fossils around 190 years ago! The day will include an informative talk with Chris followed by the fossil hunt (approximately 4 hours) to Seatown in the east, where you can catch a bus or taxi back to Charmouth. Participants will all have an opportunity to find and keep a selection of Jurassic fossils, including ammonites, belemnites and even marine reptile bones with a bit of luck!

 

Full details will be provided to participants prior to the event.

  

Adults £10 / Children £5

  

Portland dinosaur hunt - Sunday 13th July '08

Ever wished you could walk with dinosaurs? Now you can!

 

Discover the hidden secrets of Portland (Dorset), on a quarry tour with local expert and geologist Chris Pamplin, accompanied by the

Discovering Fossils & JuniorGeo team. Participants will see dinosaur trackways and foot prints, fossil trees, giant ammonites, prehistoric beaches and the Portland Sculpture park.

 

There will be some opportunities to collect fossils, but the main attraction of dinosaur footprints cannot be collected except with a camera!

 

This event requires driving between quarries. Full details will be provided to participants prior to the event.

  

Adults £10 / Children £5

 

  

Charmouth to Seatown fossil hunt - Sunday 20th July '08

A classic Jurassic fossil hunt!

 

Join local expert and geologist Chris Pamplin to explore one of the most famous stretches of the Jurassic Coast, from Charmouth to Seatown, taking in Golden Cap.

 

This classic fossil locality is where Mary Anning found many of her remarkable fossils around 190 years ago! The day will include an informative talk with Chris followed by the fossil hunt (approximately 4 hours) to Seatown in the east, where you can catch a bus or taxi back to Charmouth. Participants will all have an opportunity to find and keep a selection of Jurassic fossils, including ammonites, belemnites and even marine reptile bones with a bit of luck!

 

Full details will be provided to participants prior to the event.

  

Adults £10 / Children £5

  

Cotswold quarry fossil hunt - Saturday 26th July '08

Join local fossil expert Dr Neville Hollingworth on a guided visit of Colne Gravel Quarry in Gloucestershire to examine and collect from the highly fossiliferous Jurassic deposits. Recent finds include the bones and teeth of Ichthyosaurs, Plesiosaurs and crocodiles!. Uncrushed fossil tree trunks and branches are also common. In addition the Ice Age river gravels yield common Mammoth and other remains including horse, mammoth, deer and straight-tusked elephant bones.

 

This trip will provide everyone with an opportunity to find something rare or unusual. Following an introductory talk, participants will be able to spend a whole day on site and advice will be given on collecting and conservation techniques.

 

Full details will be provided to participants prior to the day.

   

Adults £10 / Children £5

   

Quantoxhead (Somerset) fossil hunt - Saturday 9th August '08

Join geologist Bill Verkaik on a guided tour of the famous Jurassic coast of north Somerset. Quantoxhead has yielded some of the largest and well preserved ammonites and marine reptiles in the country. The day includes an introduction to the geology and fossils of the area, followed by a guided fossil hunt along the coast. Everyone will have an opportunity to find a variety of fossils.

 

Suitable for all ages and levels of experience, including families.

 

Full details will be provided to event participants prior to the day.

 

 

    

Adults £10 / Children £5

 

Charmouth to Lyme Regis fossil hunt - Sunday 17th Aug '08

Join local expert and geologist Chris Pamplin to explore one of the most famous stretches of the Jurassic Coast, from Charmouth to Lyme Regis, taking in Black Ven.

 

This classic fossil locality is where Mary Anning found her remarkable fossils around 190 years ago! The day will include an informative talk with Chris followed by the fossil hunt (approximately 4 hours) to Lyme Regis, where you can catch a bus or taxi back to Charmouth. Participants will all have an opportunity to find and keep a selection of Jurassic fossils, including ammonites, belemnites and even marine reptile bones with a bit of luck!

 

Full details will be provided to participants prior to the event.

 

Adults £10 / Children £5

            

Future fossil hunts - register your email for event notifications CLICK HERE

      

   

 

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Safety notice: Fossil hunting can at times pose a risk to personal safety, in particular within environments close to the coast, cliffs or in quarries and when using the tools and equipment illustrated. Discovering Fossils provides a free resource to inform you about this fascinating subject and does not accept any liability for decisions made using this information. We recommend all individuals abide by the 'National Fossil Hunting Code' and independently research the potential dangers before and during the visit.

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All content and images (C) 2008 Roy Shepherd