Ruling decides boundaries of Earth’s history

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, 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.”

Controversy over when exactly theQuaternary
Period began has raged for decades, with attempts in 1948 and 1983 to define
the era. In 1983 the boundary was fixed at 1.8 million years, a decision which
sparked argument within the earth science community as this point was not a
‘natural boundary’ and had no particular geological significance.

Up to now it has been widely felt
within the scientific community that the boundary should be located earlier, at
a time of greater change in the earth-climate system.

“For practical reasons such
boundaries should ideally be made as easy as possible to identify all
around the world. The new boundary of 2.6 million years is just that,” concluded
Gibbard, “hence we are delighted at finally achieving our goal of removing the
boundary to this earlier point.”

“The decision is a very important
one for the scientific community working in the field,” said Journal Editor
Professor Chris Caseldine. “It provides us with a point in geological time when
we effectively did move into a climatic era recognisably similar to the
geological present.”