渤海湾西岸全新世沉积速率对河流供给的响应

    Holocene sedimentation rates and their response to fluvial supply on the west coast of Bohai Bay

    • 摘要: 渤海湾西岸由北向南获取了3个钻孔,以全新世海相岩心为研究对象,采用AMS 14C(Accelerator Mass Spectrometry 14C, 加速器质谱14C)测年方法建立年代框架并计算平均沉积速率,结合沉积物粒度组成及沿岸古河流三角洲发育历史,探讨了沉积速率对沿岸河流供给变化的时空响应。结果表明,早全新世—中全新世初期(11~6ka),渤海湾西岸整体沉积速率偏低,仅0.03~0.07cm/a,沉积物粒度较粗;中全新世6.43~4.97ka cal BP期间,NP3孔平均沉积速率为0.60~0.93cm/a ,高于同期沿岸南部的CH110孔和BT113孔。沉积物组成以粉砂为主,粘土含量低,向上逐渐变粗,具三角洲反粒序特征。该时段的高沉积速率系渤海湾西北岸对潮白河、永定河及滦河沉积物供给的响应;中全新世晚期3.68~2.67ka cal BP期间,BT113孔沉积速率为0.27~1.4cm/a,高于同期沿岸北部CH110孔和NP3孔,沉积物组成以粉砂为主,粘土含量较NP3孔高,向上逐渐变粗,具三角洲反粒序特征。该时段的高沉积速率系渤海湾西岸南部对黄河沉积物供给的响应;晚全新世2.29~0.24ka cal BP 期间,沿岸中部CH110孔沉积速率为0.55~0.91cm/a,高于同期沿岸南部的BT113孔和北部的NP3孔,该高沉积速率为渤海湾西岸中部对黄河和海河供给沉积的先后响应。

       

      Abstract: Taking cores from three drill holes along the western coast of Bohai Bay as the study basis and collecting materials through cutting through the upper marine bed deposited during Holocene as samples, the authors dated shells and charcoals by AMS 14C and calculated the average sedimentation rate. The spatial-temporal relationship between the Holocene sedimentation rates of drill holes and sediments transported by rivers was discussed combined with grain size and development of adjacent ancient river delta. The results indicate that various sedimentation rates occurred in different periods in Holocene and such a variety reveals different sediment supplies along the western coast of Bohai Bay. From early Holocene to early period of mid-Holocene, the low sedimentation rate (0.03~0.07cm/a) and coarse sediments along the whole western coast presented less impotent fluvial input at that time. During 6.43~4.96ka cal BP, the rising sedimentation rate (0.59~0.93cm/a) and upward-coarse grain size succession implied that Chaobai River, Yongding River and Luanhe River dumped sediments in the northern part of the west coast of Bohai Bay. In 3.68~2.67ka cal BP, the Yellow River downloaded its sediments in the southern part of the area indicated by the high sedimentation rate (0.27~1.4cm/a) and upward-coarse grain size succession, while Haihe River emptied its sediments to the middle part of the area in 2.29~0.24ka cal BP with sedimentation rate being 0.55~0.91cm/a.

       

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