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| Time Lords Announce a new Period in the Calender of Earth History |
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14 May 2004 |
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South Australia - Reference Site for a New Geological Time Period |
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The “Tim Lords” of geology (executive of the International Commission on Stratigraphy, at a meeting in Oslo Norway) have just voted to ratify a new geological period, the Ediacaran.
The layered rocks of the Flinders Ranges National Park in the north of South Australia hold the reference point for defining the base of this new period. In technical jargon, this is the Global Stratotype Section and Point (or GSSP) also known as the “Golden Spike” marking a point in a rock formation where the Ediacaran Period begins.
The name of the new period, Ediacaran, recognises the distinctive fossils that mark this period as different from the Cambrian and younger time periods. Ediacaran fossils, first discovered in 1946 by a notable South Australian geologist, the late Dr. Reg Sprigg, are the oldest known marine animals on Earth. Ediacaran fossils include our most distant animal ancestors from a time before there was life on the land, 600 to 540 million years before the present. Unlike younger fossils they had no hard parts but are preserved as death-mask impressions on sandstone layers.
The history of the Earth is recorded in rocks that have been formed ever since the Earth began to cool and had oceans. These rocks are our only means of tracing the development of the earth and its living inhabitants from their microbial origins to the complex ecosystems that cover the Earth surface today. Just as we refer to the monarchs of Britain as a means of characterizing recent human history of people of English decent, or as we refer to Stone Age, Iron Age, Atomic Age, as shorthand for human history, geologists use a common time scale to communicate their discoveries and understand the evolution of the Earth. Layered rocks, like tree rings are the physical evidence of the passing of time. Each is a unique record of climate and life of the past.
The Ediacaran Period is the first new rung in the ladder of geological time periods to be adopted in 120 years, and the first to be based on rocks in the Southern Hemisphere.
From here on, the beautifully preserved layered rocks of the Flinders Ranges will become a Mecca for geologists wishing to better understand this crucial period in the history of the Earth. Their efforts will be monitored by a new Ediacaran Subcommission of the International Commission on Stratigraphy, chaired by Dr Jim Gehling, South Australian Museum.
The Ediacaran Period marks a revolution in the history of life. Bacteria and other tiny forms of life appeared 3000 million years ago. Then, after a series of massive ice ages, life took a leap up the size scale from microbes to complex animals. Without this change 600 million years ago, we may never have evolved some 570 million years later.
Form now on students will need to invent new mnemonics for remembering the succession of geological time periods:
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Ediacaran
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