Spatial and temporal distribution of Changjiang sediments and estimation of sediment budget during the Holocene
Spatial and temporal distribution of Changjiang sediments and estimation of sediment budget during the Holocene
复制标题
DOI：
--
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
Nc State
中科院分区：
文献类型：
--
作者：
Nc State
本研究收集了长江6个主要沉积盆地的40个沉积钻孔及其年代数据以及长江口近海和大陆架的地震剖面，计算了各盆地全新世不同时期的沉积速率，估算了近7 000年的沉积物收支。 早全新世10 000—8 000 a BP期间，沉积速率为15 m/ka的主要沉积汇。中全新世以来，由于全球海平面上升，长江中下游盆地也成为沉积速率为10 m/ka的重要沉积汇。近2 000年来，近海和陆架区沉积速率明显增加，表明容量在下降。的 根据沉积速率计算，近 7 000 年来，长江中下游盆地沉积物约 13 074×10~8 吨，水下三角洲和陆架区沉积物约 9 470×10~8 吨。沉淀 全新世以来的沉积速率：1）8 000—7 000 a BP期间，所有盆地沉积均较弱；2）4 000—2 000 a BP期间，河口区出现显着的低沉积速率。我们认为这两个时期与海平面和全球气候变化事件有关。
The present study collected 40 sediment boreholes and their chronological data from the 6 major sedimentary basins of the Changjiang River and the seismic profiles from the Changjiang River mouth offshore and continental shelf,to calculate the sedimentation rates of each basin during various periods of the Holocene and to estimate the sediment budget during the last 7 000 years.The results demonstrate that the paleo-incised valley of the Changjiang River mouth was the major depositional sink with a sedimentation rate of 15 m/ka during the Early Holocene of 10 000—8 000 a BP.The middle and lower Changjiang ba- sins also became important depositional sinks with a sedimentation rate of 10 m/ka since the Middle Hol- ocene due to the global sea level rise.The sedimentation rate increased obviously in the offshore and shelf area in the last 2 000 years,indicating the decreasing of the capacity of sediment accumulation of the mid- dle and lower Changjiang basins and the estuary.Calculation,according to the sedimentation rate,indi- cates that about 13 074×10~8 ton sediments were deposited in the basins of middle and lower Changjiang and 9 470×10~8 ton in the subaqueous delta and shelf areas during the last 7 000 years.Our results also demonstrate that there were two periods of low sedimentation rates since the Holocene:1)sedimentation was weak in all the basins during 8 000—7 000 a BP;2) significant low sedimentation rate occurred in the estuarine area during 4 000—2 000 a BP.We suggest that these two periods are related with the e- vents of sea level and global climate changes.