新疆布尔津盆地晚始新世一早渐新世岩石及生物地层

布尔津盆地中的第三纪地层过去被称为“乌伦古河组”。该套地层的岩性组合独特 ,不同于乌伦古河流域该组命名剖面的乌伦古河组。依据布尔津县城西北 2 0km处的额尔齐斯河北岸出露的地层剖面 ,建立两个岩石地层单位 :下部额尔齐斯河组和上部克孜勒托尕依组。额尔齐斯河组为一套富含铁质的色彩鲜艳的碎屑堆积 ,克孜勒托尕依组是一套浅黄绿色砂岩夹杂色泥岩地层。克孜勒托尕依村附近的建组剖面为一连续沉积剖面 ,含有 3个确切的哺乳动物化石层位、5个化石地点。最下部化石层含有典型的始新世Ergilian期哺乳动物 ,其余两个层位的化石均属早渐新世Shandgolian期哺乳动物。因此 ,该剖面为一Ergilian Shandgolian(晚始新世—早渐新世 )过渡时期的地层剖面 ,是进一步研究该过渡期哺乳动物群替代及Ergilian/Shandgolian地层界线的理想剖面。

LATE EOCENE-EARLY OLIGOCENE LITHOLOGICAL AND BIOLOGICAL STRATIGRAPHY IN THE BURQIN REGION OF XINJIANG

The Burqin Basin is in the northern area of Xinjiang Uygur Autonomous Region (Fig. 1). Terrestrial beds of Tertiary are exposed along the banks of the Irtysh River that runs through the region. Most of these Tertiary beds were previously considered to be the “Ulunguhe" Formation, a rock unit that was nominated at site Sa'erduoyila south of Village Halamagai in the Ulungur River Region and have been shown to include sediments of different lithologies and different ages, ranging from late Cretaceous to Oligocene (Wu, 1973; Peng, 1975; Peng and Wu, 1983; Tong et al., 1990; Wei and Tong, 1992; Bureau of Geology and Mineral Resources of Xinjiang Uygur Autonomous Region, 1993; Ye et al., 2000, 2001a,b, 2002, 2003a,b;Wu et al., 2000; Meng et al., 2001a,b; Daxner-Hck and Wu, 2003). Our investigations during the last a few years reveal that these beds in Burqin Basin are lithologically different from but biostratigraphically correlative with the Ergilian-Shandgolian sediments in Mongolia and in Zaisan Basin of Kazakhstan. The continuous sequence may span over the Eocene-Oligocene boundary. Based on their lithological and biological contents, we propose to abandon application of the name “Ulunguhe" Formation to these sediments and to divide them into two new rock units, the Irtysh River and Keziletuogayi formations. The type section (KZ2002) is 20 km northwest to the Burqin City on the north bank of the Irtysh River, north to the Keziletuogayi village. The section measured at this locality starts at N47°50.024′, E86°40.729′ (base) and ends at N47°50.479′, E86°40.912′ (top) and is described below: Quaternary System 29.Grayish white, fluvial, poorly sorted quartz conglomerates