Limites do período Quartenário pré-histórico foram modificados

End Of An Era: New Ruling Decides The Boundaries Of Earth's History

ScienceDaily (Sep. 23, 2009) — After decades of debate and four years of investigation an international body of earth scientists has formally agreed to move the boundary dates for the prehistoric Quaternary age by 800,000 years, reports the Journal of Quaternary Science.

The decision has been made by the International Commission on Stratigraphy (ICS), the authority for geological science which has acted to end decades of controversy by formally declaring when the Quaternary Period, which covers both the ice age and moment early man first started to use tools, began.

In the 18th Century the earth's history was split into four epochs, Primary, Secondary, Tertiary, and Quaternary. Although the first two have been renamed Palaeozoic and Mesozoic respectively, the second two have remained in use by scientists for more than 150 years. There has been a protracted debate over the position and status of Quaternary in the geological time scale and the intervals of time it represents.

"It has long been agreed that the boundary of the Quaternary Period should be placed at the first sign of global climate cooling," said Professor Philip Gibbard. "What we have achieved is the definition of the boundary of the Quaternary to an internationally recognised and fixed point that represents a natural event, the beginning of the ice ages on a global scale."
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Journal reference:

Gibbard, P.; Head, M. Formal ratification of the Quaternary System/Period and the Plestocene series/Eoch with a base at 2.58 Ma. Journal of Quaternary Science, 2009.