杭嘉湖平原早中全新世相对海平面重建及海岸带响应

发布时间：2018-06-08 19:17

本文选题：全新世早中期 + 杭嘉湖平原　；参考：《华东师范大学》2015年硕士论文

【摘要】：21世纪海平面加速上升是目前人类不能忽视的问题。地质历史时期中得到的经验,将有助于预测本世纪末及未来海平面加速上升如何影响河口海岸带沉积地貌的演化。世界各地学者研究得出,全新世是最后一次冰期结束、气候转暖时期。全新世的早中期全球海面迅速上升,到距今6000年前接近现今位置,其后仅有微小的变化。因此,研究全新世早中期海平面上升过程及河口地貌响应,可指导我们如何应对海平面快速上升所带来的海岸带环境变化。前人研究显示,因长江三角洲平原的特殊性,重建全新世相对海平面曲线用基底泥炭和地层学方法较为可行。本论文通过对长江三角洲南部的杭嘉湖平原10个全新世钻孔的岩性、粒度特征以及微体古生物(孢粉、藻类)分析来精细识别全新世地层,并寻找适合本区海平面定量重建的有效指示物。通过对有效指标(基底盐沼泥炭和高潮滩沉积相)进行测年与古海平面定量分析,重建杭嘉湖平原全新世早中期相对海平面曲线,并通过对钻孔沉积相演变研究揭示海岸带沉积地貌对海平面变化的响应。研究显示,本区在9600 cal a BP左右海平面还处在现今海平面以下29m处,到6800 cal a BP,海平面已上升到与现今海平面相差不大的高度。且9600-8700 cal a BP,其海平面上升速率达到11mm/a; 8700-8400 cal a BP,海平面上升速率更是达到18mm/a; 7800-7400 cal a BP短短400年上升了5.2m之多,杭嘉湖平原地区海平面上升速率达到13.2mm/a。由于水均衡和沉积物均衡调整等作用的影响,研究区早中全新世相对海平面与世界各地同时期相对海平面不同,且高于太湖平原东部钻孔所得的相对海平面。杭嘉湖平原全新世早中期主要为潮滩环境,随海平面上升速率的改变而发生退积或加积和进积。9600-7750 cal a BP,海平面上升速率略微大于研究区沉积速率,潮滩发生退积,杭嘉湖平原由高位盐沼向高潮滩演化；而7750-7450 cal a BP期间,沉积速率远小于海平面上升速率,杭嘉湖平原潮滩继续退积,普遍演变为中低潮滩;直到7450-6800 cal a BP时期,海平面上升速率下降,杭嘉湖平原又开始加积形成高潮滩。
[Abstract]:The accelerated rise of sea level in twenty-first Century is a problem that human beings cannot ignore at present. The experience gained in geological history will help to predict how the sea level acceleration at the end of the century and in the future will affect the evolution of sedimentary geomorphology in the estuary and coastal zone. Scholars around the world have concluded that the Holocene was the last ice period and the climate warming. In the early and middle period of the Holocene, the global sea level rose rapidly, approaching the present position 6000 years ago and only minor changes. Therefore, the study of the sea level rise process and the estuarine geomorphic response in the early Holocene can guide us to cope with the coastal environment changes caused by the rapid rise of sea level. Previous studies have shown that the Yangtze River is three. It is more feasible to reconstruct the Holocene relative sea level curve with the method of base peat and stratigraphy to reconstruct the Holocene relative sea level. In this paper, the lithology, grain size characteristics and micropaleontology (sporopollen, algae) of the 10 Holocene boreholes in the hang Jia Lake Plain of the south of the Changjiang Delta were analyzed to identify the Holocene strata and find the suitable one. The effective indicator of regional sea level quantitative reconstruction is to reconstruct the relative sea level curve of the early and middle Holocene in the Hangzhou Jiagan Lake Plain by quantitative analysis of the effective index (base salt marsh peat and high tide beach sedimentary facies) and the paleo sea level, and to reveal the response of the sedimentary geomorphology of the coastal zone to the sea level change through the study of the evolution of the borehole sedimentary facies. The study shows that the sea level in the area around 9600 cal a BP is still at 29m below the present sea level, and to 6800 cal a BP, the sea level has risen to a high altitude of the present sea level. And the sea level rise rate of 9600-8700 cal a BP is up to the 11mm/a; the rate of sea level rise is reached more than that of the sea level; 7800-7400 A BP has risen more than 5.2m in just 400 years. The sea level rise rate of the hang Jia Lake Plain has reached 13.2mm/a. due to the effect of water balance and sediment balance adjustment. The relative sea level in the early Middle Holocene is different from the relative sea level in the world at the same time in the world, and is higher than the relative sea level in the east of the Taihu plain. The early and middle Holocene epoch of the Jiahu plain is mainly the tidal flat environment. With the change of the sea level rising rate, the accretion or accumulation and accumulation of.9600-7750 cal a BP, the sea level rising rate is slightly greater than the deposit rate in the study area, the tidal flat is degrading, the hang Jia Lake Plain evolves from high salt marsh to the high tide beach, while the deposition of 7750-7450 cal a BP is deposited. The rate is far less than the rising rate of the sea level. The tidal flat of the hang Jia Lake Plain continues to deceit and generally evolves into the middle and low tidal flat. Until the 7450-6800 cal a BP period, the rise rate of the sea level drops, and the hang Jia Lake Plain begins to accumulate to form a high tide bank.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P534.632;P736.22

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