Fossil Hunting Information
The trendy use of the word ‘fossil’ refers to the physical proof of prehistoric life that's preserved from a time period prior to recorded human history. There is no universally agreed age at which the proof may be termed fossilised, nonetheless it’s broadly understood to encompass anything more than just a few thousand years. Such a definition consists of our prehistoric human ancestry and the ice age fauna as well as more historical fossil groups such as the dinosaurs, ammonites and trilobites.
Fossils happen commonly around the globe although just a small proportion of former life made it into the fossil document, maybe less than a billionth. Most dwelling organisms merely decayed with out trace after death. Thus, Cretaceous the abundance of fossils displays the immense number of organisms which have lived and the vast size of time over which the rocks have accumulated.
The earliest fossils discovered date from 3.5 billion years ago, nonetheless it wasn’t until roughly 600 million years ago that complicated multicellular life started to enter the fossil record, and for the needs of fossil hunting the vast majority of effort is directed towards fossils of this age and more recent.
The geologic timescale is split into eras which are additional divided into intervals, of which probably the most incessantly quoted is the Jurassic period (from the Mesozoic period) – well-known for the abundance of dinosaurs at this time. To view the geologic timescale
Step one towards understanding the place to look for fossils is to appreciate the distribution of fossil bearing rocks and the circumstances that led to their formation and subsequent exposure. The rocks reveal the circumstances present on the time of their formation and the forces that subsequently influenced their character.
There are three major rock types: sedimentary, fashioned from gathered sediment, e.g. sand, silt and skeletal stays; igneous, shaped 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 discovered within sedimentary rocks due to the favourable circumstances of burial and limited alteration via time. Sedimentary rocks form on the Earth’s surface as sediment accumulates in rivers, lakes and on the seafloor in particular. Among the widespread sedimentary rocks embrace: sandstone, composed predominantly of grains of eroded rock; limestone, composed predominantly of shell debris and planktonic skeletons; and shale, fashioned from hardened clay (originally deposited as mud).
Sedimentary rocks could undergo considerable change tens of millions of years after deposition leading to a new rock type, e.g. slate. These ‘altered’ rocks are collectively often known as metamorphic. Slate was originally laid down as a muddy sediment which was then compacted and hardened to type shale (a sedimentary rock), over time the shale was exposed to better pressure and heat within the ground, a results of continental movement and/or tectonic activity. Over time the fabric of the shale was altered, changing the original material and converting it to a metamorphic rock, consequently fossils within the slate are sometimes flattened and distorted.
On very rare occasions fossils will also be discovered within igneous rocks the place molten rock escapes to the Earth’s surface and envelops organisms in its path, corresponding to a tree. In this example if the molten rock cools and hardens in less time than it takes to show the tree to ash, then the hardened rock might form a strong mould across the tree. Over a short time frame the tree tissues decay leaving an empty chamber inside the rock, some examples even protect the feel of the outer bark on the walls of the mould.
Having recognised unaltered sedimentary deposits as the primary source for fossils, the following step is to understand where such rocks are located. Geology maps are a helpful place to start as they reveal the age and type of rocks present on the surface; note that the surface rock is generally underlain by older rocks unless significant geological forces have caused buckling/folding of the landscape.