On the northern fringe of Mt. Huangshan, many river terraces are developed at the junction between mountains and plains. The river terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang...On the northern fringe of Mt. Huangshan, many river terraces are developed at the junction between mountains and plains. The river terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang River, one of the longest tributaries of the lower Yangtze River, developed three staircase terraces. The topmost terrace(i.e., the T3 terrace) tread is 38-39 m above river level, and the top of the gravels is generally covered by 3-10.9 m of red clay deposits. Systematic magnetostratigraphy and electron spin resonance dating are used to research the timing of the establishment of the Qingyijiang River. The main results show that the topmost terrace developed no later than 900 kyr ago and that the appearance of the Qingyijiang River occurred correspondingly at least before 900 kyr ago on the northern fringe of Mt. Huangshan. In view of the almost synchronous age,the establishment of the Qingyijiang River was seemingly a response to the Mid-Pleistocene Revolution when the 100 kyr cycle commenced, and the Kunlun-Huanghe movement during the earlymiddle Pleistocene transition. In addition, the establishment of the Qingyijiang River possibly reflected the birth of the modern Yangtze River to some degree. Therefore the timing of the formation of the Yangtze River is restricted to no later than 900 kyr ago based on the appearance of the Qingyijiang展开更多
青弋江是长江下游最大的一条支流,发源于安徽省黄山北麓。野外考察发现青弋江在泾县段共发育了三级河流阶地,其中最高阶地(T3)存在两个天然剖面,即CB-T3剖面和SJ-T3剖面。运用电子自旋共振(ESR)测年法,并结合相关文献资料,确定青弋江泾...青弋江是长江下游最大的一条支流,发源于安徽省黄山北麓。野外考察发现青弋江在泾县段共发育了三级河流阶地,其中最高阶地(T3)存在两个天然剖面,即CB-T3剖面和SJ-T3剖面。运用电子自旋共振(ESR)测年法,并结合相关文献资料,确定青弋江泾县段最高阶地的形成年代并探讨其构造气候意义。研究结果表明:青弋江泾县段最高阶地的年代约900 ka B.P.,是早中更新世过渡时期河流作用的产物;青弋江泾县段900 ka B.P.阶地是可能是构造抬升和东亚夏季风变化共同作用下的产物,其中构造抬升为阶地的形成提供了河流下切的动力条件,而东亚夏季风的强度变化为阶地的形成提供了气候条件。研究结果有助于为长江中下游地区的河流地貌研究提供基础数据和参考资料。展开更多
基金financially sponsored by the National Natural Science Foundation of China(Grant No.41301011,41301029,41201008)
文摘On the northern fringe of Mt. Huangshan, many river terraces are developed at the junction between mountains and plains. The river terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang River, one of the longest tributaries of the lower Yangtze River, developed three staircase terraces. The topmost terrace(i.e., the T3 terrace) tread is 38-39 m above river level, and the top of the gravels is generally covered by 3-10.9 m of red clay deposits. Systematic magnetostratigraphy and electron spin resonance dating are used to research the timing of the establishment of the Qingyijiang River. The main results show that the topmost terrace developed no later than 900 kyr ago and that the appearance of the Qingyijiang River occurred correspondingly at least before 900 kyr ago on the northern fringe of Mt. Huangshan. In view of the almost synchronous age,the establishment of the Qingyijiang River was seemingly a response to the Mid-Pleistocene Revolution when the 100 kyr cycle commenced, and the Kunlun-Huanghe movement during the earlymiddle Pleistocene transition. In addition, the establishment of the Qingyijiang River possibly reflected the birth of the modern Yangtze River to some degree. Therefore the timing of the formation of the Yangtze River is restricted to no later than 900 kyr ago based on the appearance of the Qingyijiang
文摘研究不同空间尺度的景观组成与结构对水质的影响对于水质保护具有重要意义。青弋江为长江下游最长的支流,人类活动可能通过多种方式对水质产生影响。以青弋江流域为研究对象,基于Google Earth遥感数据和水质实测数据,采用冗余分析(RDA)和Spearman相关性分析,探讨了土地利用/景观格局对水质的影响。研究结论为:(1)以采样点为中心建立的100、200、500、1000、2000 m 5种尺度缓冲区中,500 m半径圆形缓冲区景观组成对水质的解释率最高,枯水期与丰水期对水质的解释率分别为46.30%和43.10%。(2)土地利用类型中,耕地和建设用地面积与NH4+-N、TP、EC呈正相关,对水质具有负面效应;林地面积与DO呈正相关,对污染物起到净化作用;土地利用综合程度指数与污染指标呈正相关,表明人类活动强的区域,水质变差。(3)景观格局指数中,PRD在丰水期与NH4+-N、TP浓度为负相关,相关系数分别为-0.656、-0.540,表明随斑块丰富度密度的增大,流域生态系统更加稳定;LPI与DO浓度在枯水期为显著负向相关,相关系数为-0.653,SHAPEAM与NH4+-N、TP呈显著正向相关,表明随人类活动强度的增大,水质恶化;FRACAM与水质的关系无法得到合理的解释。通过多角度分析,在一定程度揭示了青弋江流域的生态水文过程,有利于土地利用管理和水质保护,进而促进资源的可持续利用。研究结果可为政府相关职能部门进行决策时提供参考。
文摘青弋江是长江下游最大的一条支流,发源于安徽省黄山北麓。野外考察发现青弋江在泾县段共发育了三级河流阶地,其中最高阶地(T3)存在两个天然剖面,即CB-T3剖面和SJ-T3剖面。运用电子自旋共振(ESR)测年法,并结合相关文献资料,确定青弋江泾县段最高阶地的形成年代并探讨其构造气候意义。研究结果表明:青弋江泾县段最高阶地的年代约900 ka B.P.,是早中更新世过渡时期河流作用的产物;青弋江泾县段900 ka B.P.阶地是可能是构造抬升和东亚夏季风变化共同作用下的产物,其中构造抬升为阶地的形成提供了河流下切的动力条件,而东亚夏季风的强度变化为阶地的形成提供了气候条件。研究结果有助于为长江中下游地区的河流地貌研究提供基础数据和参考资料。
