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| 青藏高原东缘晚新生代大邑砾岩的 物源分析与水系变迁* | |
| 引用本文： | 黎兵,李勇,张开均,张玉修,张毅,魏庆国,汪洋.青藏高原东缘晚新生代大邑砾岩的 物源分析与水系变迁*[J].第四纪研究,2007,27(1):64-73. |
| 作者姓名： | 黎兵 李勇 张开均 张玉修 张毅 魏庆国 汪洋 |
| 作者单位： | 1. 中国科学院广州地球化学研究所与南海海洋研究所边缘海地质重点实验室,广州,510640;中国科学院研究生院,北京,100049 2. 成都理工大学油气藏地质及开发工程国家重点实验室,成都,610059 3. 中国科学院广州地球化学研究所与南海海洋研究所边缘海地质重点实验室,广州,510640;南京大学地球科学系,南京,210093 |
| 基金项目： | 中国科学院"百人计划" , 国家自然科学基金 |
| 摘 要： | 成都盆地晚新生代碎屑沉积物的快速堆积是青藏高原东缘强烈隆升的产物,同时为青藏高原东缘晚新生代的隆升提供了强有力的证据。文章以盆地底部的大邑砾岩作为研究切入点,详细研究了它的物源区,以深化对青藏高原东缘晚新生代隆升过程的理解。通过砾石成分统计、砂岩薄片鉴定、重矿物分析以及古流向恢复等方面的研究表明,成都盆地北部和南部的大邑砾岩分别受不同的物源区和河流所控制。其中北部的大邑砾岩受控于出口在都江堰南约4km处向南流的河流所控制,其物源区为玉堂镇以西、汶川-茂汶断裂以东的流域范围内。而南部的大邑砾岩则主要受向东流的古青衣江的控制,其物源区即为现代青衣江流域。大邑砾岩的物源分析表明晚新生代期间岷江和青衣江都曾发生河流改道。 |
| 关 键 词： | 青藏高原东缘 晚新生代 成都盆地 大邑砾岩 物源分析 水系变迁 |
| 文章编号： | 1001-7410（2007）01-64-10 |
| 收稿时间： | 2006-05-08 |
| 修稿时间： | 2006-07-26 |
PROVENANCE OF THE SILICICLASTIC ROCKS OF THE LATE CENOZOIC DAYI FORMATION AND DRAINAGE CHANGE AT EASTERN MARGIN OF THE TIBETAN PLATEAU |
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| Li Bing,Li Yong,Zhang Kaijun,Zhang Yuxiu,Zhang Yi,Wei Qingguo,Wang Yang.PROVENANCE OF THE SILICICLASTIC ROCKS OF THE LATE CENOZOIC DAYI FORMATION AND DRAINAGE CHANGE AT EASTERN MARGIN OF THE TIBETAN PLATEAU[J].Quaternary Sciences,2007,27(1):64-73. | |
| Authors: | Li Bing Li Yong Zhang Kaijun Zhang Yuxiu Zhang Yi Wei Qingguo Wang Yang |
| Institution: | (Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry ＆ South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou510640|Graduate University of Chinese Academy of Sciences, Beijing100049|State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu610059|Department of Earth Sciences, Nanjing University, Nanjing210093) |
| Abstract: | The uplift of the Tibetan Plateau has long been a hot topic, but some of its aspects still remain open to intense debate. This study attempts to offer some insights into the understanding of the process of the uplift from the eastern margin of the Tibetan Plateau. The eastern edge of the Tibetan Plateau is marked by the Longmen Mountain, which experienced pronounced denudation in the Late Cenozoic and was previously attributed to river erosion. According to published literatures, most of its eroded material was output into the Sichuan Basin. The Chengdu Basin, located in the southwest of the Sichuan Basin, could be thus the basin accommodated most of the deposits. Sediments deposited in the Chengdu Basin during the Late Cenozoic were assumed to be mainly controlled by the uplift of the eastern Tibetan Plateau rather than the climate and/or the lithology of the provenance area. Studies on the pro￣venance of the upper Cenozoic siliciclastic rocks in the Chengdu Basin can thus provide key constraints on the uplift timing of the Tibetan Plateau. Sedimentary analyses for both the upper Cenozoic siliciclastic rocks and sediments in modern rivers were conducted both in the field and in the laboratory. The upper Cenozoic profiles, characterized by the Dayi Formation, are located along the margin of the eastern Tibetan Plateau, mainly in the west of the Chengdu Basin. We investigated two in the east of the basin. Two profiles of modern rivers are located near Dujiangyan city to the north and near Ya'an city to the south respectively. Pebble count and paleocurrent analysis for the upper siliciclastic rocks were done in the field, which provided some interesting information about their original areas. For example, with the boundary of the northern and southern Chengdu Basin defined between Jindongzi and Qionglai, the Dayi Formation in the northern and southern parts are distinctly different in their original area, and both are derived from the Longmen Mountain to the west. In order to get further knowledge about the original areas, sandstone samples, cropped out as lenticles in the Dayi Formation, were taken in the field and cut for observation under microscope. Some were also minced for heavy-mineral analysis. For comparison, modern sands were also analyzed. As a result, it is found that the content of garnet in the modern Min Jiang is particularly higher than that of any other samples, even than that of the upper Cenozoic samples nearby. It could be an important and helpful implication, making sense in determining the drainage change of ancient Min Jiang. The results of grain fragments analysis of sandstone and heavy-mineral analysis largely support the understanding deduced from the pebble count and paleocurrent analysis, and they further indicate that the Dayi Formation in the northern Chengdu Basin was transported from the area between the Wenchuan Fault and Yutang town where is about 4km south to Dujiangyan city, whereas that in the southern Chengdu Basin was from the drainage area of modern Qingyi Jiang. The drainages of the Min Jiang and the Qingyi Jiang are considered diverted during the Late Cenozoic according to provenance analysis on the Dayi Formation. |
| Keywords: | Eastern Tibetan Plateau Late Cenozoic Chengdu Basin Dayi Formation provenance analysis river diversion |
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