摘要
泥河湾盆地东谷坨剖面的环境磁学研究表明泥河湾盆地湖相地层的物源具有多重性,既有来自周边山地的风化碎屑,又有来自西北和北方沙漠地区的粉尘物质,导致了其古环境和气候记录的复杂性。湖相地层除记录了松山反极性时晚期和布容正极性时这两个大的极性时段以外,还记录了哈拉米洛极性亚时和另外3个短期极性漂移事件。磁组构参数表明东谷坨剖面的地层是在正常的重力分异条件下沉积的,且自沉积结束以来没有受到明显的后期扰动。磁化率最大轴的方位角显示东谷坨剖面处乃至泥河湾盆地东部的古水流方向主要(或大多数时候)为北北西-南南东向。
The Nihewan Basin is known for possessing the type sections of lacustrine strata of Late Cenozoic in Northern China, with abundant fossils of mammalian fauna, mollusk, pollen, and plentiful human remains. The environmental evolution accompanied with the development of the Nihewan paleolake has attracted interests of geoscientists for a long time. The Donggutuo section lies in the northeastern margin of the Nihewan Basin, where the lake-floor deposits were more influenced by lake inlet. Two Paleolithic sites, Donggutuo and Maliang, are located in the section. The Donggutuo site is one of the most extensively excavated and prolific sites yet studied in the Nihewan Basin. Based on a well constructed magnetostratigraphic chronology of the Donggutuo section, environmental magnetism study is carried out on the lacustrine strata, to indicate the paleoenvironmental status in the process of deposition, especially in the period of early human inhabitation. Environmental magnetism investigations of lacustrine sediments at the Donggutuo section indicate that the deposition of the Nihewan Basin has multiple source origins, resulting in a complexity of the records of paleoenvironment and paleoclimate. Sedimentary materials include not only particles weathered from the mountains in the vicinity, but also dust from desert far in the northern and northwestern of China. The lacustrine sediments at the Donggutuo section recorded not only large polarity chrons including the late Matuyama reversal Chron and Brunhes normal Chron, but also Jaramillo polarity subchron and three other short polarity excursions. Magnetic fabric parameters suggest that the strata of the Donggutuo section had been deposited under the normal conditions of gravity differentiation, and had not been disturbed obviously since the deposition was finished. Statistical analysis of azimuths of the maximum axis of magnetic susceptibility ellipsoid reveals that the paleocurrent directions were oriented concentratedly（or in the most periods）at NNW-SSE at the place of the Donggutuo section, or even in the east part of the Nihewan Basin. Lacustrine sediments can faithfully record the past variations of geomagnetic field, deposition settings, and climatic environment, although they might have been mixed and difficult to be differentiated. Further studies are required to disclose the paleoclimate and paleoenvironment imprints on the Nihewan beds.
出处
《第四纪研究》
CAS
CSCD
北大核心
2007年第6期1081-1091,共11页
Quaternary Sciences
基金
中国博士后科学基金项目(批准号:20060390091)
国家自然科学基金项目(批准号:40221402和40325011)资助
关键词
环境磁学
磁组构
河湖相地层
东谷坨剖面
泥河湾盆地
environmental magnetism, magnetic fabric, lacustrine-fluvial sediments, Donggutuo section, Nihewan Basin
