Pre-Cambrian/Cambrian Unconformity

 

Speculation and even heated debate have attended the study of earth's history. The Cambrian/Pre-Cambrian event is no exception.

Pre-Cambrian fossils are rare and seldom well preserved.

The boundary between Pre-Cambrian and Cambrian strata is often, but not always, clearly defined. In the rare instances where it is not clearly defined, one investigator's opinion may differ from another's regarding its exact position.

It seems reasonable to make the following generalisations:-

  • The event of which the Pre-Cambrian/Cambrian Unconformity bears record was world-changing and occurred between five and six hundred million years ago.
  • The most complex fossils currently assigned to the Pre-Cambrian include internally semi-symmetrical structures no larger than a pencil dot, and enigmatic slug and jellyfish-like remains.
  • There is no proof of Pre-Cambrian life more complex than that of plants. Organisms such as those illustrated here have not been shown to be anything more than 'organised seaweed'.
  • Truly complex -- that is, animal-grade-life -- first leaves a record in the Cambrian. Every division of complex life, including the vertebrates, is represented in Cambrian strata. In the case of the vertebrates, these earliest representatives were embryonic and almost unrecognisable as vertebrates. In other divisions of life, such as the sea insects and various sea shells, the Cambrian representatives were, in some cases, highly sophisticated.
  • Not long before the termination of the Pre-Cambrian there was a significant increase in the complexity of some living organisms.

The engine behind the breaking forth of complex, animal-grade life during the earliest Cambrian is investigated elsewhere on this site. This leaves another intriguing question. Why did the (simple, plant-grade) life of the Pre-Cambrian begin to increase in complexity before the main Pre-Cambrian/Cambrian Event?

If a major planetary event, such as that suggested for the explosion of complex life, was a factor in the information signalling requisite to the creation and revelation of complex species, could a lesser planetary event have played a part in the advance of plant-grade life immediately prior to the main Event?

It is here suggested that capture, by the earth, of various ice-bodies contributed to increased quantum electro-magnetic signalling at that time. These ice-bodies may also have served as cushions in the moon introduction event and as a standing source of supply for the earth's atmosphere as the newly created organisms drew on its supply of essential elements such as carbon.

 

 

 

 

................................

Bottjer, D.J. 2005, 'The Early Evolution of Animals', Scientific American, Aug. 2005, Vol. 293, No. 2, pp. 30-35.

Reader, J. 1986, The Rise of Life, William Collins & Sons, London. Illustrations by John Gurche.