| 早更新世松花江水系反转 |
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| 引用本文： | 魏振宇,谢远云,康春国,迟云平,吴鹏,王嘉新,张曼,张月馨,刘璐.早更新世松花江水系反转[J].沉积学报,2020,38(6):1192-1203. |
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| 作者姓名： | 魏振宇 谢远云 康春国 迟云平 吴鹏 王嘉新 张曼 张月馨 刘璐 |
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| 作者单位： | 1.哈尔滨师范大学地理科学学院，哈尔滨 150025 |
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| 基金项目： | 国家自然科学基金项目41871013, 41601200 |
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| 摘 要： | 水系重建对于理解全球变化和区域响应至关重要。松花江水系演化研究极为薄弱，尤其对第四纪早期松花江水系是否发生倒转一直存在争议，且无明确证据。河流沉积物是水系演化最直观的证据。为此，选择哈尔滨荒山（HS）钻孔岩芯沉积物作为研究对象，对其进行了磁化率、古地磁和Sr?Nd同位素组成分析。结果表明，岩芯62.3 m（0.94 Ma B.P.）深度上、下地层的磁化率和Sr?Nd同位素特征存在较大差异。62.3 m以下地层磁化率极低，多次出现0值，且变幅较小。Sr?Nd同位素组成与依兰方向现代水系的Nd同位素特征相近；然而62.3 m以上地层磁化率急剧增大，并呈现周期性的高低变化。Sr?Nd同位素组成小幅度变化，表现出与松原方向现代水系相近的Nd同位素特征。表明了早更新世晚期松花江中上游（肇源—依兰河段）水系流向曾发生反转。早更新世早—中期，松花江中上游与下游尚未贯通。以佳依（佳木斯—依兰）分水岭为界，松花江下游向东流经三江平原，而松花江中上游向西流入松嫩湖盆；早更新世晚期，由于构造—气候变化的共同作用，佳依分水岭不断抬升，而三江平原和松嫩平原持续下降，导致分水岭两侧河流向源侵蚀，在0.94 Ma B.P.，佳依分水岭被切穿，松花江中上游水系被下游水系所袭夺，流向开始倒转，中上游与下游贯通，现代松花江水系逐渐建立。
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| 关 键 词： | 松花江 水系演化 荒山岩芯 Sr?Nd同位素 物源示踪 佳依分水岭 |
| 收稿时间： | 2019-07-25 |
The Inversion of the Songhua River System in the Early Pleistocene: Implications from Sr?Nd isotopic composition in the Harbin Huangshan cores |
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| Institution: | 1.College of Geographic Science, Harbin Normal University, Harbin 150025, China2.Heilongjiang Province Key Laboratory of Geographical Environment Monitoring and Spatial Information Service in Cold Regions, Harbin Normal University, Harbin 150025, China3.Geography Department, Harbin Institute, Harbin 150086, China |
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| Abstract: | Drainage evolution reconstruction is crucial for understanding global change and the regional response. As the most important river in northeast China， the study of the evolution of the Songhua River system is extremely weak. Whether the water system of the Songhua River reversed in the early Pleistocene has been especially controversial and without clear evidence. As a direct product of river geological processes， sediment is the most direct evidence of the water system evolution. Located in the east Songnen Plain and the middle reaches of the Songhua River， Harbin has an arid?semiarid temperate continental climate. Located in the eastern suburb of Tuanjie town， Daowai district， Harbin city， the Huangshan （HS） belongs to the second?order terrace on the right bank of the Songhua River geomorphology The evolution information of its sediment provenance can provide direct evidence for the study of the formation and evolution of the Songhua River， especially for the inversion of the Songhua River system. Therefore， magnetic susceptibility， paleomagnetic， and Sr?Nd isotope composition analysis of sediments from boreholes core in the HS are performed. The results showed that the magnetic susceptibility and Sr?Nd isotope characteristics of the upper and lower strata at a core depth of 62.3 m were significantly different. The magnetic susceptibility of the strata below 62.3 m is extremely low， and 0 value appears many times with only a small variation in range. The Sr?Nd isotope composition differ sharply above and below the mean value of the core. However， the magnetic susceptibility of the strata above 62.3 m increased sharply， and showed periodic high and low changes. And the isotopic composition of Sr?Nd varied slightly. Through the comparison with the Nd isotope composition of the upper and lower strata of 62.3 m in the rock core of Huangshan Mountain， we observe that the Nd isotope characteristics of the strata below 62.3 m are similar to those of the modern river system in the direction of Yilan?Tonghe. The Nd isotope characteristics of the Nenjiang River， second Songhua River， Lalin River， and Kule River systems are similar to those of the 62.3 m above. It indicates that the river direction in the middle and upper reaches of the Songhua River （Zhaoyuan?Yilan reach） was reversed in the late early Pleistocene.To summarize， the following evolution model of the Songhua River system is proposed: In the early and middle early Pleistocene， the upper and lower reaches of Songhua River were not connected. Bounded by the Jiayi （Jiamusi?Yilan） watershed， the lower reaches of the Songhua River flow eastward through the Sanjiang Plain， while the upper reaches of the Songhua River flow westward into the Songnen Lake basin. In the late early Pleistocene， due to the combined effect of tectonic?climate change， the Sanjiang and Songnen Plains continued to decline， while the Jiayi watershed continued to rise， leading to the erosion of rivers on both sides of the watershed to the source. At the same time， affected by 0.9 Ma in the Pleistocene climate transformation， headward erosion at 0.94 Ma B.P.， the watershed is cut to wear. The Songhua River shelter?forest system was captured by the downstream drainage and began to reverse the Songhua River shelter?forest and downstream， the Songhua River shelter?forest river from west to east through better in canyon in Sanjiang plain， and the Songhua River shelter?forest and downstream river， thus linking modern Songhua River water system gradually established. |
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