LHASA, May 7 (Xinhuanet) -- Fossils suggest that Ngari Prefecture,the peak of Tibet Autonomous Region, known as the "roof of the world", was once a land where the climate was mild and humid, and plenty of big arbors were grown some 130 million years ago.

¡¡¡¡The silicified arbor fossils, believed to be from the early Cretaceous Period, were discovered by research workers with the Institute of Geoscience of Chengdu Science and Engineering University during a geological survey into the Qinghai-Tibet LoessPlateau last August.

    The fossils were hidden into the tuff sandstone of the early Cretaceous Period in Gerze County of Ngari Prefecture. And the silicified wood stem well preserves features of the tree for growth: the trunk taking a cylindrical shape with a diameter between 20 cm to 40 cm, and the growth ring of the tree could be seen on the open section, but quite vaguely, said Professor Liu Dengzhong with the Institute of Geoscience.

    Pieces of plant fossils and fresh-water shell fossils were alsodiscovered from the strata where the silicified wood fossils were found. However, scientific researchers found fossils of halobios such as corals from newer strata above the strata containing silicified wood fossils, which suggests the environment in Ngari underwent changes later.

    Most of the present-day Ngari Prefecture are 4,500 meters abovethe sea level. The natural conditions are bad and climate is arid there.

    Excavation of the fossils present people with a quite differentpicture of Ngari in ancient times, said Liu, adding the fossils would be of great significance to studying geography, climate and environmental changes of Ngari in prehistoric ages. Enditem