Knowledge Resource Center for Ecological Environment in Arid Area
| 内蒙古准格尔旗红粘土序列的成因、年代及其古气候意义 | |
| 冯少华 | |
| 出版年 | 2010 |
| 学位类型 | 硕士 |
| 导师 | 杨石岭 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 本论文主要对内蒙古准格尔旗红粘土沉积进行了粒度、颜色、土壤形态和古地磁研究。粒度结果显示，准格尔旗红粘土序列的粒度分布及统计参数（分选系数、偏度和峰度）与灵台、泾川剖面的第四纪古土壤、新近纪红粘土十分类似。土壤学证据表明，准格尔旗红粘土为加积型古土壤，并发育有铁锰胶膜、粘粒胶膜和成壤碳酸盐。以上证据均表明准格尔旗剖面为风成成因。磁性地层和碳同位素地层研究表明，准格尔旗剖面古地磁极性序列可与标准极性柱的C3n.1r~C3An.2n极性段相对应，其沉积时代为4.13~6.61Ma，平均沉积速率为2.53cm/ka。\n准格尔旗剖面是迄今为止有年龄报道的纬度最高的红粘土沉积，表明黄土高原主体地区红粘土的北界至少在现代毛乌素沙漠以北，其分布北界比黄土更靠北。结合已有资料，我们重建了黄土高原主体地区红粘土的分布范围，初步估算其面积约为22万km2，说明新近纪已有一相当规模的粉尘源区。\n空间粒度对比表明，红粘土的粒度分异远远小于第四纪黄土－古土壤序列，表明新近纪粉尘沉积区至源区的距离远大于第四纪时期。红粘土的南北向颜色（a*，红度）梯度亦远远小于古土壤S1，暗示晚新近纪气候梯度小于第四纪间冰期。 |
| 英文摘要 | A 62-m-thick ‘red clay’ sequence was discovered recently at Jungar Banner (39°55′N，110°57′E) in Inner Mongolia, northern China. It consists of 45 paleosol units and 46 carbonate nodule layers. This study presents grain size, color reflectance, soil morphological features and palaeomagnetic dating results for the Jungar Banner ‘red clay’. Grain size analysis shows that in most soils, the median grain size are centered at about 4~8 μm with the sand fraction being negligible. Overall, the ‘red clay” shows grain-size characteristics very similar to well-developed Pleistocene paleosols (e.g. S5), all being broad and flat curves. Paleosols within the ‘red clay’ are accretionary in nature with various amounts of clay coatings, black Fe-Mn coatings and pedogenic carbonate. These evidence all suggest an eolian origin for the ‘red clay’ sequence. \nOver 260 orientated samples were collected at an interval of 20~25cm from the ‘red clay’ sequence. The magnetic remanence was measured with a 2G-760 U-channel system in the Institute of Geology and Geophysics, Chinese Academy of Science. In addition, we measured the δ13C of 46 carbonate nodules in order to constrain the paleomagnetic polarity, since a significant C4 plant expansion at 4 Ma is well documented in the ‘red clay’ sediment on the Loess Plateau. The δ13C record indicates a major expansion of C4 plants at the depth of 3m. The combined results from magnetostratigraphy and isotope stratigraphy demonstrate that the polarity zones of the Jungar Banner section correlate with those between C3n.1r and C3An.2n of the GPTS, yielding an age range of 4.13~6.61Ma and a relatively constant sedimentation rate of 2.53cm/ka.\nThe Jungar Banner section is the northernmost ‘red clay’ sequence so far found in the main body of the Loess Plateau, implying the northern distributional limit of the Neogene ‘red clay’ can be extended at least to the north of the present-day Mu Us desert. In other words, the northern distributional limit of the ‘red clay’ is located further north than that of the Pleistocene loess. The synthesis of spatial data allows us to construct a map of ‘red clay’ distribution for the main body of the Loess Plateau, from which a distribution area of 2.2×105 km2 is conservatively estimated. Such a large area ‘red clay’ deposition requires a vast dust source region in central Asia during the late Neogene.\nIn contrast to a steep north-south gradient in grain size of Pleistocene loess-soil sequences, the ‘red clay’ shows a slight spatial change in its particle size, indicating a greater dust transport distance in the late Neogene than in the Quaternary. In addition, the ‘red clay’ shows a spatial gradient in redness (a*) much lower than that of the last interglacial soil (S1), indicating a slighter climate gradient in the late Neogene than in the last interglacial period. |
| 中文关键词 | 红粘土 ; 粒度 ; 磁性地层 ; 色度 ; 碳同位素 |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 第四纪地质学 |
| 来源机构 | 中国科学院地质与地球物理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286836 |
| 推荐引用方式 GB/T 7714 | 冯少华. 内蒙古准格尔旗红粘土序列的成因、年代及其古气候意义[D]. 中国科学院大学,2010. |
| 条目包含的文件 | 条目无相关文件。 | |||||
| 个性服务 |
| 推荐该条目 |
| 保存到收藏夹 |
| 导出为Endnote文件 |
| 谷歌学术 |
| 谷歌学术中相似的文章 |
| [冯少华]的文章 |
| 百度学术 |
| 百度学术中相似的文章 |
| [冯少华]的文章 |
| 必应学术 |
| 必应学术中相似的文章 |
| [冯少华]的文章 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
