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"Frontier geology" uncovers Mesozoic Asia: Continents clashed while dinosaurs roamed

In the Mesozoic era when dinosaurs roamed Asia, the ground beneath their feet was on the move.

Massive chunks of the Earth's restless crust smashed into the continent, adding much of present-day China, Tibet and Southeast Asia onto a land mass that ended the Paleozoic era with its coastline somewhere south of present-day Mongolia. Mountain ranges were formed as Tibet crashed northwards into China. Sections of crust were pushed 100 kilometers below the surface as the South China Block thrust under the North China Block. A volcanic island arc stretched from present-day southern China to the Bering Straits. The center of the continent was pressed together and stretched apart like an accordion ­ much like the Basin and Range region of the United States.

Meanwhile, basins filled with sediment, burying the remains of gigantic creatures and the tropical vegetation they fed on ­ organic matter that would gradually be transformed into China and Mongolia's present-day oil fields. asiageo1.jpeg

Photos courtesy of Stephan Graham Lab, Stanford University

A volcanic event 130 million years ago petrified this tree in present-day Mongolia, along with the forest surrounding it. Geologists, left to right, are graduate student Laura Webb, Professor Stephan Graham and graduate student Cari Johnson.

That is part of the picture that emerges from scientific work to be presented by a group of Stanford scholars on Tuesday, Oct. 21 at the Geological Society of America meeting in Salt Lake City. Their poster session describes the forces that shaped Asia during the complicated and dynamic Mesozoic era (245 - 65 million years ago). It is based on work by the six authors and their Stanford colleagues, a progress report on a dozen years' study of the geology of Asia.

It is also based on adventure: Stanford students and their professors gathered these data by jeep, on horseback and on foot in Chinese deserts hotter than California's Death Valley: Mongolian plains inhabited by nomadic horsemen; Siberian mountains, and Chinese agricultural valleys where foreigners still are a rare sight.

"Stanford probably has had the longest and largest presence of any U.S. university in studying the geology of the eastern half of Asia," said Stephan Graham, professor of geological and environmental sciences. Since the Chinese, Mongolian and Russian governments opened their doors to collaboration with Western scholars in the mid-'80s research groups led by eight Stanford faculty members have conducted field studies in regions from the Bering Strait to the border of Vietnam, from the Pacific coast as far west as Tibet, Mongolia and northwest China. asiageo2.jpeg

Graduate student Brad Ritts inspects an oil seep at Huotugou, in the Qaidam Basin of Northwest China.

"The result has been innovative and groundbreaking science, much of it done for the first time," Graham said. "It includes contributions to regional geology and to fundamental principles."

Graham credits the initiative of a group of graduate students for bringing together this progress report at the GSA meeting ­ and the geologic data base that underlies it. Nearly five years ago, graduate students started meeting weekly for a seminar on Asian geology, where Stanford and visiting scholars present a wide range of work on Asian geology in sessions that often turn into contentious discussions of the complex geologic history of the region. Under the leadership of its 1996/97 chairs, doctoral candidates Todd Greene and Laura Webb, the seminar has become a vehicle for focusing on the Mesozoic "time slice" ­ a period when many of the resources that Asian countries seek to exploit, including gold and oil, were formed. Much of the East Asian land mass was shaped at this time, before the much more well-studied Cenozoic era when India began crashing into Tibet to form the Himalayas.

The GSA poster session covering that "time slice" is based on nine dissertations and more than 150 publications by Stanford authors. It will be presented by Greene, Webb and fellow graduate students Cari Johnson ­ chair of this year's seminar ­ and Jeremy Hourigan. Two co-authors ­ Graham and graduate student Brad Ritts ­ remain at Stanford. asiageo3.jpeg

Graduate student Todd Greene investigates a vein of Jurassic coal, formed from former Mesozoic swamps in the Turpan-Hami Basin of Northwest China.

While the Stanford scientists collaborate with Asian scientists who have already conducted studies in many of these regions, the continent is so vast that much of the research is based on data collected for the first time, or collected with techniques that previously had not been applied there.

"This is frontier geology," said Greene. "It's sort of akin to what the original geologists saw as they came through the Western U.S.: the incredible mountains, the canyons. [Unlike them] we have our Asian colleagues to help us out, but this represents the first time that this geology has been described and made available to the worldwide scientific community."


By Janet Basu

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