LATE CENOZOIC MAGNETOSTRATIGRAPHY (11-0 MA) OF THE DONGSHANDING AND WANGJIASHAN SECTIONS IN THE LONGZHONG BASIN, WESTERN CHINA

A paleomagnetic study of the 510-m-thick Wangjiashan section of Late M iocene and Pliocene terrestrial sediments reveals a fairly complete re versal record with ages from 11 to 1.8 Ma. The magnetostratigraphy of the Dongshanding section, located nearby, reveals a partially overlapp ing reversal record with ages from 2.2 to 0 Ma, and facilitates correl ation of the Wangjiashan section with the global polarity time scale. A new stratigraphic division of the Wangjiashan section replaces the n ame Linxia formation by five new formation names, based on lithologic variation and mammalian fossil finds. The new formations and their mag netostratigraphically determined ages are: Dongshan Formation (c. 1.75 -2.6 Ma), Jishi Fm. (c. 2.6-3.6 Ma), Hewangjia Fm. (4.5-6.0 Ma), Liush u Fm. (6.0-7.6 Ma), and Dongxiang Fm. (7.6-c. 12 Ma). The Neogene stra tigraphy and fossil mammals suggest that the nearby part of the Tibeta n Plateau experienced a persistent denudation during the Late Miocene and Early Pliocene, but that it was uplifted more rapidly at about 3.6 Ma.