QX01孔记录的渤海湾西岸沿海低地MIS3晚期以来的河道充填与环境演化

发布时间：2018-02-12 20:31

  本文关键词： 古河道 环境演化 沿海低地 渤海湾　出处：《地学前缘》2016年04期 　论文类型：期刊论文

【摘要】：在渤海湾沿海低地地区获得1个30m的全取心机械钻孔(QX01孔),对样品进行了沉积岩石学分析、底栖有孔虫鉴定、硅藻鉴定和粒度分析,结合AMS 14 C和OSL测年,重建了研究区晚更新世以来的古河道充填及环境演化过程。结果显示QX01孔自下而上可以分为6段:(1)30~29.72 m,陆相洪泛沉积;(2)29.72~29.4m,海侵沉积,43.5ka BP;(3)29.4~17.7m,砂质沉积物,河道填充沉积,37.9~29.7ka;(4)17.7~13.2m,沉积物由砂质变为黏土质,29.7~8ka,由河道填充转为浅湖沼环境;(5)13.2~5m,8~4ka,全新世海侵沉积,沉积环境由陆相转为海陆过渡相,6 000~5 750cal BP海侵达到最强,之后逐渐退出该区;(6)5m以上,洪泛沉积,约1.7ka至今。沉积环境与海面具有很好的响应,MIS 4或6阶段时,海面较低,河流下切,形成古河道,下切最深处位于现代高程为-24.2m。MIS3阶段早期时,海面上升,37.9ka河道开始填充,至29.7ka填充完成,对应高程为-11.8m。末次盛冰期至早全新世时为浅湖沼环境,沉积作用停止或速率非常低。随着末次盛冰期的结束,海洋作用增强,进入全新世海侵沉积阶段,8~4ka cal BP。之后,沉积作用停止,至1.7ka以来,随着河流作用的不断增强,该区变为河流控制的洪泛沉积为主。同时,发现了两次沉积间断,分别发生在末次盛冰期的低海面时期和4~2ka时的海水退出、河流沉积尚不充分时期。
[Abstract]:A 30m full coring machine drill hole QX01 was obtained in the coastal lowland area of Bohai Bay. The samples were analyzed by sedimentary petrology, benthic foraminifera identification, diatom identification and particle size analysis, combined with AMS 14C and OSL dating. The course of paleochannel filling and environmental evolution since the late Pleistocene in the study area has been reconstructed. The results show that the QX01 hole can be divided into 6 sections from the bottom to the top of the study area. The results show that the QX01 hole can be divided into 6 sections: 1 / 1, 30 ~ (30) ~ 29.72 m, 2 ~ (29. 72) m of continental flood sediment, 43.5 ka B ~ ((1)) B ~ ((1)) of transgressive sediment, 329.417 ~ (7) m of sand sediment. The fluvial sediment was filled with 37.9 ~ 29.7 ka / L ~ (4) ~ (17. 7) m ~ (17. 7) m, the sediment changed from sandy to clay (29. 7 ~ 8 ka) and changed from river filling to shallow lake and marsh environment. The sediment was transgressive in Holocene, and the sedimentary environment reached its maximum from 6 000 to 6 000 ~ 5 750 cal BP transgression, and then gradually withdrew from the area to more than 65 m. Flood deposition, about 1.7 ka to the present. The sedimentary environment and sea surface have a good response to the MIS 4 or 6 stage, and the sea level is lower, and the river is cut down, forming paleochannel, the deepest of which is in the early stage of the modern elevation of -24.2m.MIS3. The upper sea level began to fill up at 37.9ka, and the filling was completed at 29.7ka, corresponding to -11.8m. from the last glacial to the early Holocene, there was a shallow lake-marsh environment, and the sedimentation stopped or the rate was very low. With the end of the last glacial period, the oceanic action increased. After entering the transgressive sedimentary stage of Holocene, 4ka cal BP. the sedimentation stopped, and since 1.7ka, with the increasing of fluvial action, the area has become fluvial controlled flood sedimentation. At the same time, two sedimentary discontinuities have been found. It occurred in the low sea stage of the last glacial age and the sea water exit at 4 ~ 2 ka, respectively, while the fluvial deposition was not sufficient.
【作者单位】： 中国地质调查局天津地质调查中心;中国地质调查局泥质海岸带地质环境重点实验室;天津地质矿产研究所现代沉积物测年实验室;天津师范大学城市与环境科学学院;中国社会科学院考古研究所;
【基金】：国家自然科学基金面上项目(41476074) 中国地质调查局项目(1212011120169)
【分类号】：P736
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本文编号：1506495