滦河三角洲晚全新世地层和演化过程

为了更好地理解滦河三角洲晚全新世沉积演化过程,本文对8个钻孔进行了年代学、沉积学、微体古生物学的研究,并结合1984～2016年研究区的遥感影像特征,恢复了滦河三角洲晚全新世发育过程和模式。2.7 ka B.P.以前,研究区发育湖相三角洲前缘,包括河床和水下河道相;2.7～1.0kaB.P.,伴随着海平面上升,海岸线达到现今滦河三角洲一带,姜各庄林场以西区域发育湖相三角洲,包括湖沼相、湖滨相和分支河道、河间洼地等,东部形成海侵型砂坝-潟湖海岸地貌沉积体系;约1.0 kaB.P.以来研究区域普遍成陆,西部主要为决口扇和河间洼地相,东部多分支河道相;17～19世纪,翡翠岛-姜各庄林场一带形成海岸沙丘,并造成二滦河、老米沟等河流由东折向南入海;1915 A.D.,滦河冲开姜各庄林场至翡翠岛的海岸沙丘,形成现今波浪型三角洲。研究区经历了3期地貌沉积组合:晚全新世组合包括西部湖相三角洲和东部海侵型砂坝-潟湖海岸地貌沉积体系;17～19世纪的组合包括三角洲平原和翡翠岛-七里海海侵型砂坝-潟湖海岸地貌沉积体系;1915 A.D.后的组合包括三角洲平原、翡翠岛-七里海海侵型砂坝-潟湖海岸地貌沉积体系和...

The Late Holocene stratum and evolution in the Luanhe River Delta

The Luanhe River originates from the foothills of Bayantuer in Fengning County in Hebei Province,and empties into the Bohai Sea through the Yanshan Mountains.It had undergone many diversions during the historical period,forming alluvial fan-delta in different scales with apex in Tingliuhe,Qian'an and Luanxian.The alluvial fan-delta of the Luanhe River is adjacent to Yanshan in the north and the Bohai Sea in the south.It is structurally located in the transitional zone between the Huanghua Depression and the Yanshan Uplift Belt.By analyzing the sedimentary process and development pattern of the Luanhe River Delta in the Late Holocene,we can understand the response process of the Luanhe River Delta under future global changes better.In order to understand the sedimentary evolution process in the Luanhe River Delta in the Late Holocene better,eight boreholes were analyzed in chronology,sedimentology,micropaleontology and grain size.Boreholes LQZ14,LQZ20,LQZ26,LQZ29 and LQZ30 with lengths ranging from 3 m to 5 m were obtained by the Eijkelkamp manual sampling drill.Sediments with depth of 0~10 m in boreholes LZK01,LZK04 and JZK13 with lengths ranging from 50 m to 75 m are analyzed in this study,because that the depth of the Holocene strata is approximately 10~20 m.27 samples for micropaleontology and 52 samples for grain size analysis were used to establish sedimentary facies,7 AMS 14C ages used to establish era framework.And based on the characteristics of the remote sensing image of the study area from 1984 to 2016,the development process and the pattern of the Luanhe River Delta in the Late Holocene were recovered.Before 2.7 cal.ka B.P.,the lacustrine delta front,including the riverbed facies and the underwater channel facies,had developed in the study area.During 2.7~1.6 cal.ka B.P.,with the sea level rising,the coastline had reached the present-day Luanhe River Delta.The western area of the Jianggezhuang Forest Farm had developed the lower delta facies of the lacustrine delta and deltaic plain facies,including the lacustrine facies,marsh facies,the lakeside facies,branch channel facies and the crevasse splay,respectively.And in the east it had formed the transgressive barrier-lagoon geomorphic sedimentary system.Since 1.0 cal.ka B.P.,the study area had generally formed lands,the western areas were mainly the interfluvial lowland and the crevasse splay,and most of the eastern areas were branch channel facies.From the 17th century to the 19th century,coastal dunes had formed around the area of Feicuidao-Jianggezhuang Forest Farm,and had caused the rivers such as Erluanhe River and Laomigou to turn from the east to the south.The Luanhe River rushed apart the coastal dunes of Feicuidao-Jianggezhuang Forest Farm and formed the current wavy delta in 1915 A.D.The study area has experienced three-phase geomorphic sedimentary combinations.The Late Holocene combination included the western lacustrine delta and the eastern transgressive barrier-lagoon geomorphic sedimentary system.The combination from the 17th century to the 19th century included the delta plain and the transgressive barrier-lagoon geomorphic sedimentary system of Feicuidao-Qilihai.The combination after 1915 A.D.included the delta plain,the transgressive barrier-lagoon geomorphic sedimentary system of Feicuidao-Qilihai and the wavy delta.