Fossil hunting is a fascinating pastime enjoyed by families and individuals of all ages and levels of experience. With just a little time spent learning the basics anyone can enjoy the thrill of finding evidence of prehistoric creatures and the environments they lived in.
What is a fossil?
The modern use of the word 'fossil' refers to the physical evidence of prehistoric life that is preserved from a period of time prior to recorded human history. There is no universally agreed age at which the evidence can be termed fossilised, however it's broadly understood to encompass anything more than a few thousand years. Such a definition includes our prehistoric human ancestry and the ice age fauna as well as more ancient fossil groups such as the dinosaurs, ammonites and trilobites.
The earliest fossils discovered date from 3.5 billion years ago, however it wasn't until approximately 600 million years ago that complex multicellular life began to enter the fossil record, and for the purposes of fossil hunting the majority of effort is directed towards fossils of this age and more recent.
Where do you look for fossils?
The first step towards understanding where to look for fossils is to appreciate the distribution of fossil bearing rocks and the conditions that led to their formation and subsequent exposure. The rocks reveal the conditions present at the time of their formation and the forces that subsequently influenced their character.
There are three primary rock types: sedimentary, formed from accumulated sediment, e.g. sand, silt and skeletal remains; igneous, formed from molten rock that has cooled and hardened; and metamorphic, sedimentary or igneous rocks that have been altered significantly by heat and/or pressure.
Fossils are most commonly found within sedimentary rocks due to the favourable conditions of burial and limited alteration through time. Sedimentary rocks form on the Earth's surface as sediment accumulates in rivers, lakes and on the seafloor in particular. Among the common sedimentary rocks include: sandstone, composed predominantly of grains of eroded rock; limestone, composed predominantly of shell debris and planktonic skeletons; and shale, formed from hardened clay (originally deposited as mud).
Sedimentary rocks may undergo considerable change millions of years after deposition resulting in a new rock type, e.g. slate. These 'altered' rocks are collectively known as metamorphic. Slate was originally laid down as a muddy sediment which was then compacted and hardened to form shale (a sedimentary rock), over time the shale was exposed to greater pressure and heat within the ground, a result of continental movement and/or tectonic activity. Over time the fabric of the shale was altered, replacing the original fabric and converting it to a metamorphic rock, consequently fossils within the slate are often flattened and distorted.
On very rare occasions fossils can also be found within igneous rocks where molten rock escapes to the Earth's surface and envelops organisms in its path, such as a tree. In this example if the molten rock cools and hardens in less time than it takes to turn the tree to ash, then the hardened rock may form a solid mould around the tree. Over a short period of time the tree tissues decay leaving an empty chamber inside the rock, some examples even preserve the texture of the outer bark on the walls of the mould.
Having recognised unaltered sedimentary deposits as the main source for fossils, the next step is to understand where such rocks are located. Geology maps are a useful place to start as they reveal the age and type of rocks present at the surface; note that the surface rock is generally underlain by older rocks unless significant geological forces have caused buckling/folding of the landscape.
What if you don't have the time or resources to find real fossils? Can you collect replica fossils?
Yes, you will be able to find replica fossils on internet sites such as Ebay. While you are waiting to fill up your specimen cupboard with real fossils why not add a few replicas such as the ones shown below?
This full Mammoth skeleton is one of the best replica fossils you will find and is available for sale in my ebay store.
This large shell fossil looks almost exactly the same as the real one in the first photo of this document. But it is available in my store at a fraction of the price of a real one.
This replica fossil is of a trilobite and again, you can hardly tell it apart from the real thing. So you can see that collecting replica fossils can be just as exciting as collecting the real thing. They also make very unique Christmas presents for young boys or girls.