During the period, known as the early Cambrian period, this region, like the rest of the earth's surface, was covered predominantly by water except for two small, separate lands sticking out in today's southwestern China.

Over the following 100 million years, the two separate lands began to move towards each other and finally collided. Known as Kangdian, it formed part of what is today's Yunnan-Guizhou Plateau and Qinghai-Tibet Plateau in China.

Most of the world's land, however, was part of the southern super-continent Gondwana.

The Cambrian period witnessed an explosion of life in its early stage, with invertebrates beginning to appear.

The climate was still mild in the early and mid Ordovician period and it was not until later that glaciers began to take central stage.

The ocean was thriving with diverse marine invertebrates, red and green algae, primitive fish and corals, while the land was still a lifeless place.

The ocean floor around today's southern China was also undergoing dramatic changes during this time, which are vividly illustrated in the atlas.

"This may be a good illustration of a well-known Chinese saying that describes the constantly changing world, 'Ocean at one time, land at another'," said Feng, a professor at the Beijing-based University of Petroleum.

This atlas is one of a series compiled by Feng and his colleagues that cover the palaeogeography of the major part of China in the Cambrian and Ordovician periods.

Published consecutively over the last couple of years, they are the most accurate and detailed atlases of the palaeogeography of China so far.

The atlases are generally on a scale of 1:5,000,000, more than three times larger than that of normal atlases, which means much more detail of the Earth's surface can be illustrated on the map.

When read together, the atlases present a vivid and complete panorama of the geographic changes of China during the Cambrian and Ordovician periods over 500 million years ago.

More than just illustrations for scientific journals and books, the atlases provide useful clues for prospecting for natural resources like oil and coal, Feng said.

The distribution of these natural resources is invariably associated with palaeogeographic changes of the earth.

The more we learn about them, the more likely we may find the natural resources we need, said Liu Benpei, a professor at the University of Geology in Beijing.

A good palaeogeography atlas can save a lot of money and time when exploring for natural resources.

"Drilling a well, for example, may take 10 million yuan (US$1.2 million) yet it may turn out to be without oil," Liu said.

"With the same amount of money we could compile very good atlases of palaeography that can lead to much better explorative results and less money being spent."

In fact, Feng's focus on the southern China atlas is part of a long-term effort to look for oil and natural gas in the region, where prospecting has been carried out for years, but little progress has been made due to a poor understanding of the palaeogeography.

Since the mid 1990s, Feng and his colleagues have come out with 17 atlases that revealed the geological changes of China in diverse periods, some providing direct clues to oil prospecting.

Their atlas of the Erdos Plateau in northern China in the early Palaeozoic period, published in the early 1990s, formed the theoretic basis for the prospecting and discovery of a large reserve of natural gas.

Yet Feng's ambition goes beyond the Ordovician and Cambrian periods.

During a national symposium on paleogeography held last month in Beijing, Feng and several other scientists proposed to compile a set of atlases to cover the palaeogeography of the whole of China from the Changcheng period about 1.85 billion years ago to the period when civilization emerged.

It is to consist of maps and comprehensively demonstrate the geographic conditions in various periods.

"Not only the land and ocean, but fauna and flora should be demonstrated according to their times and locations," Feng noted.

When it comes to the emergence of civilization, the influence of human activities over the geography should also be reflected, said Liu Jiyuan, a researcher at the Institute of Earth Science and Resources Research, who has seconded the proposal.

This plan, if carried out, will significantly deepen our understanding of the earth, said Liu from the University of Geology.

Twenty years ago, Liu was involved in the compilation of the "Atlas of China's Palaeogeography."

The award-winning publication consists of 143 maps and remains the most comprehensive of its kind.

The first such atlas was published in 1955 and compiled by Liu Hongyun, based primarily on fossils of marine life.

Both of the atlases only cover the Cambrian and Ordovician periods and are of a relatively small scale due to limited material.

With the huge amount of palaeogeographic information accumulated over the past two decades, it is time to compile a new, larger set of atlases, Feng said.

To do that, a national project ought to be initiated to involve experts and researchers from various disciplines of earth science, he added.

Feng said the proposal was submitted to the central government after the symposium closed.

It will take 6 to 8 years to complete the work if everything goes smoothly, he predicted.

"Its use for scientific research and in practice will manifest not at the present time, but the many years to come," Feng said.

(China Daily January 29, 2003)