河北平原廊固凹陷ACX03孔晚上新世以来地层与沉积*

基于河北平原廊固凹陷东北部ACX03孔(深300.0 m)浅部¹⁴C年龄和磁性地层,建立钻孔第四纪地层格架,依据ACX03孔岩心沉积物、测井曲线和微体古生物特征划分沉积层段并分析沉积环境。研究结果表明: ACX03孔B/M(布容/松山)、M/G(松山/高斯)极性界线分别位于83.8 m、220.2 m,孔底年龄约3.2 Ma,划分13个沉积层段。上新统(220.2~300.0 m)为河道、河漫滩夹湖泊沉积,下更新统(85.2~220.2 m)为河道、湖泊、河漫滩沉积,中更新统(61.5~85.2 m)为分支河道夹河漫滩及河间洼地—湖沼沉积,上更新统(23.2~61.5 m)为河漫滩、分支河道沉积,全新统(0~23.2 m)为泛滥平原、河曲—牛轭湖沉积。对比ACX03孔与邻近钻孔第四纪地层认为,河北平原廊坊—固安一带早更新世差异性沉降最强,之后一直到全新世越来越弱。

Stratigraphy and sedimentary facies of Borehole ACX03 at Langgu sag in Hebei Plain since the Late Pliocene

Base on the ¹⁴C age and magnetic stratigraphy of Borehole ACX03 with the depth of 300.0 m,and is located in the northeast part of Langgu sag,Hebei Plain,the Quaternary stratigraphic framework of borehole was established. Based on the core sediment, logging curves and micropaleontological characteristics,the paper divided sedimentary intervals and analyzed sedimentary environment of Borehole ACX03. The results show that: the B/M and M/G polarity boundaries of Borehole ACX03 are located at 83.8 m and 220.2 m,the age of the hole bottom is about 3.2 Ma,13 sedimentary intervals was divided. The Pliocene(220.2~300.0 m)in Borehole ACX03 was river and floodplain deposit which mingle Lakes deposit,the Lower Pleistocene(85.2~220.2 m)was river,lake and floodplain deposit,the middle Pleistocene(61.5~85.2 m)was branched channel deposit which mingle floodplain and interfluvial-limnetic deposit,the Upper Pleistocene(23.2~61.5 m)was floodplain and branched channel deposit,and the Holocene(0~23.2 m)was flood plain and curved-oxbow lake deposits. Comparison of the Quaternary strata of Borehole ACX03 and adjacent boreholes shows that the differential subsidence of the early Pleistocene is strongest,and then it gets weaker and weaker until the Holocene in Langfang-Gu’an area of Hebei Plain.