全新世海侵以来现行黄河口区域沉积层序及古气候演化

Sedimentary Sequences and Paleoclimatic Evolution of the Current Yellow River Mouth Area Since Holocene Transgression

本文对位于现行黄河口深度30.73m的BH6钻孔粒度分布、岩性特征、常量元素、有孔虫介形虫种类及分布、14 C年代进行了分析,讨论了研究区全新世海侵以来的沉积层序和古气候演化。钻孔连续记录了近黄河口区域全新世海侵以来的沉积历史,从上至下可以分为5个沉积相,(1)(0~4.87m)为河口三角洲前缘亚相,(2)(4.87~8.08m)为前三角洲相沉积,(1)(2)共同组成三角洲相沉积,(3)(8.08~12.08m)应为近岸浅海沉积,(4)(12.08~23.85m)为河口边滩至潮坪相沉积,(5)(23.85m~)为陆相湖泊沉积。利用钻孔常量元素特征比值对古气候演化进行讨论,认为全新世海侵期以来BH6钻孔古气候总体经历了相对暖-温凉-暖-温凉的过程。

The size distribution,lithological characteristics,major elements,species and distribution of foraminiferal insects,carbon-14 dating of the 30.73 m long BH6 borehole located in the current Yellow River estuary are analyzed,and the sedimentary sequences and paleoclimatic evolution since the Holocene transgression in the study area are discussed.The borehole has recorded the sedimentary history of the area near Yellow River estuary since the Holocene Transgression,and it can be divided into five sedimentary facies from top to bottom:(1)(0~4.87 m)the first one is the estuarine delta front subfacies,(2)(4.87~4.87 m)the second one is the former delta sedimentary facies,and together they form the delta sedimentary facies,(3)(8.08~12.08 m)the third one is the nearshore shallow sea sedimentary facies,(4)(12.08~23.85 m)the fourth one is the estuary beach to tidal flat facies,(5)(23.85 m~)the fifth one is the continental lake sedimentary facies.The characteristic ratio of the major elements in the borehole is used to discuss the paleoclimate evolution,and it is considered that since the Holocene transgression,the paleoclimate of the BH6 borehole has experienced an overall process of a relatively warm climate to a cold climate,back to a warm climate,and then to a cold climate again.