China presents a challenge to the paleogeographer because all but 9% of this huge country has been tectonically deformed between the Jurassic and the present. Even the undeformed areas--the Sichuan basin of south China, the Ordos basin of north China, and the Tarim and Dzungarian basins of west China--have thrust-loaded margins. The present geometry of China resulted from the accretion to Asia during the late Paleozoic to the early Cenozoic of three moderate-size continents (Yangtze, Sino-Korean, and Tarim) as well as numerous smaller continental fragments in the region of the Tibetan Plateau. As might be expected, the present collision pattern of India with Asia and the resultant thrusting of western China and "continental escape" of eastern China by transtensional syste s became manifest during some of these earlier collision episodes.

Is there any hope of "untying the Gordian knot" and reconstructing this complicated history with any confidence? Chinese geologists have been able to date the collisions of the constituent microcontinents by studying the ophiolite and flysch sequences. Their biogeographic studies would point to Gondwana as the most likely source of these continental elements. Also, Chinese geologists have been assiduous in describing the rich stratigraphic record of their country, so it is possible to deduce from the distribution of the climatically sensitive sediments the approximate paleolatitudes of the microcontinents during their transits of Tethys. This information can be compared with paleomagnetic results that are just becoming available. The sea-floor-spreading history of the Indian Ocean pro ides some constraints, but prior to the collision of India in the Eocene, China was completely surrounded by subduction zones and therefore detached from the ocean floor.

The general picture then is the accretion in succession, from north to south, of microcontinents, of which India is the most recent arrival. Left-lateral deformation between and within these elements was a recurrent

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pattern from the Jurassic onward. Subduction zones formed on the southern and eastern margins of the accreting Asian continent, but the eastern arcs were of an extensional nature. The timing of this back-arc extension varied from place to place, i.e., Late Jurassic in the Songliao basin of northeast China, Cretaceous in the basin-and-range-type extension in southeast China, and middle to late Tertiary in the Japan Sea, Bohai, Subei, East China Sea, and South China Sea basins of the entire eastern perimeter of the continent.

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