Fossils

Fossils

I. What’s a fossil?
The word “fossil: refers to the physical evidence of former life from a period of time prior to recorded human history. This prehistoric evidence includes thefossilised remains of living organisms, impressions and moulds of their physical form, and marks/traces created in the sediment by their activities.
The earliest reported fossil discoveries date from 3.5billion years ago, however it wasn't until approximately 600 million years ago that complex multi-cellular life began to enter the fossil record.
Fossils occur commonly around the world although just asmall proportion of life makes it into the fossil record. Most living organisms simply decay without trace after death as natural processes recycle their soft tissues and even hard parts such as boneand shell.

II. How do fossils form?
The term 'fossilisation' refers to a variety of often complex processes that enable the preservation of organic remains within the geological record. Itfrequently includes the following conditions:
A. Rapid and permanent burial/entombment - protecting the specimen from environmental or biological disturbance;
B. Oxygen deprivation - limiting theextent of decay and also biological activity/scavenging;
C. Continued sediment accumulation as opposed to an eroding surface - ensuring the organism remains buried in the long-term
D.Absence of excessive heating or compression which might otherwise destroy it.

III. Where are they found?
Fossil evidence is typically preserved within sediments deposited beneath water, partly becausethe conditions outlined above occur more frequently in these environments, and also because the majority of the Earth's surface is covered by water (70%+). Even fossils derived from land, includingdinosaur bones and organisms preserved within amber (fossilised tree resin) were ultimately preserved in sediments deposited beneath water i.e. in wetlands, lakes, rivers, estuaries or swept out to...