摘要
通过近20年在新疆乌伦古河和额尔齐斯河流域新生代地层及哺乳动物化石的调查研究,对准噶尔盆地北缘的新生代地层分布和年代日渐清晰。研究表明,该地区堆积了大体连续的上始新统至上中新统近顶部的地层,地层中含有多个层位较为丰富的哺乳动物化石,为探明该区域的哺乳动物演化和地质环境变迁提供了难得的机会。其中位于乌伦古河南岸的夺勒布勒津台地西缘,出露了索索泉组顶部、哈拉玛盖组和可可买登组地层,记录了从红色泥质粉砂为主体的风成堆积转换为浅灰绿色河湖相堆积,最后演变为土黄色砾岩为主体的河流相堆积的过程;其中所含的索索泉组顶部、哈拉玛盖组和可可买登组这3个化石层位的相应动物群组合与山旺期上部、通古尔期下部和通古尔期中部的哺乳动物群相当,亦表明气候环境从干冷转变为相对暖湿又逐渐转向干冷的过程。2009年实测地层剖面和采集古地磁样品测定建立的磁性地层相当于C5Cr~?C5AAn,约为16.8~13.5 Ma。区域上和剖面上的化石研究显示,通古尔期化石组合始于哈拉玛盖组底部,位于磁性地层相当于C5Cr(16.726~17.277 Ma)内,年代大约为16.8 Ma,与中中新世气候适宜期的底界大体吻合。为此建议将17 Ma作为通古尔期的底界,并推荐将新疆夺勒布勒津剖面作为通古尔阶的候选层型剖面。本研究将讨论与此相关的系列问题。
During the past 20 years,based on the investigation of the Cenozoic strata and mammalian fossils along the Ulungur and IrtyshRiver basins in Xinjiang,the Cenozoic strata and their ages on the northern margin of the Junggar Basin have become increasingly clear.Our study reveals that the Cenozoic deposits are nearly continuously deposited from the Late Eocene to Late Miocene,with abundant mammalian fossils in several horizons,providing a rare opportunity to explore mammalian evolution and palaeoenvironmental changes in the area.Particularly,on the western edge of the Duolebuljin terrace on the south bank of the Ulungur River,the Suosuoquan,Halamagai,and Kekemaideng formations records the transition from aeolian deposits dominated by red mudstone and silt to shallow grey-green lacustrine deposits,and finally to fluvial deposits dominated by yellow-brown conglomerate.The corresponding fossil assemblages in the six fossil layers are comparable to the mammalian fauna of the upper Shanwangian,lower Tunggurian,and middle Tunggurian,indicating a transition from dry and cold,to relatively warm and humid,and again back change to drying and colding.The magnetic polarity can be will correlated to C5Cr~?C5AAn,equivalent to 16.8~?13.5 Ma.Mammalian fossil assemblage of Tunggurian begins at the bottom of the Halamagai Formation,corelating to C5Cr(16.726~17.277 Ma),with an approximate age of 16.8 Ma,which roughly coincides with the lower boundary of the optimum climate period of the Middle Miocene.Considering that the animal assemblage is controlled by the climate background,We suggested considering 17 Ma should as the beginning of the Tunggurian period,and recommend the Duolebuljin section in Xinjiang as a candidate stratotype section for the Tunggur stage.In addition,we also discussed the issues of climate change related to the stratigraphy involved in the study.
作者
叶捷
付娇
王世骐
YE Jie;FU Jiao;WANG Shiqi(Key Laboratory of Vertebrate Evolution and Human Origins,Institute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of Sciences,Beijing 100044)
出处
《第四纪研究》
CAS
CSCD
北大核心
2024年第6期1509-1521,共13页
Quaternary Sciences
基金
国家重点研发计划项目(批准号:2023YFF0804500)
中国科学院古脊椎动物与古人类研究所“十四五”重点部署项目共同资助。