河北平原三河S9孔岩心特征及第四纪地层划分研究

第四纪地层年代学格架的建立对区域地层对比及古地理环境演化研究具有重要意义。通过分析河北大厂凹陷北部第四系标准孔S9钻孔岩心沉积物颜色、结构构造、岩性组合特征,应用测井曲线、古地磁、AMS ¹⁴C和OSL测年方法,对S9钻孔剖面进行详细地层划分、沉积相分析和地层年代学格架建立。将S9孔揭示的松散沉积物分为4套岩性组合:第1套岩性组合代表洪积扇沉积;第2套岩性组合代表辫状河沉积;第3套岩性组合代表洪积扇沉积;第4套岩性组合代表泛滥平原沉积和河床沉积。通过对古地磁实验结果的分析得出, 0~145.3 m为古地磁极性带的布容正极性时,145.3~212.6 m为古地磁极性带的松山反极性时,212.6~251.8 m为古地磁极性带的高斯正极性时。以磁性地层为主导,以岩性地层特征、¹⁴C和OSL测年数据为辅,对S9孔第四纪岩性地层进行初步划分,其第四纪地层的下更新统、中更新统和上更新统的底界对应深度分别为210.9 m、145.4 m和24.05 m。

Core Characteristics and Stratigraphic Classification of Borehole S9 in Sanhe,Hebei Plain

Establishing Quaternary stratigraphic chronological framework is of great significance to regional stratigraphic correlation and paleogeographic environment reconstruction. According to the sediment colors, structures, and lithological characteristics of borehole S9 in the northern Dachang Depression, together with well-logging, paleomagnetism, ¹⁴C and OSL dating, detailed stratigraphic division, sedimentary facies, and stratigraphic chronological framework are established. This work focused on dividing the loose sediments of S9 into four assemblages: (1) diluvial fan deposit; (2) braided river deposit; (3) diluvial fan deposit; (4) flood plain and riverbed deposit. Paleomagnetic data show that the 0-145.3 m interval is Brunhes normal polarity chron, 145.3~212.6 m interval is Matuyama reversed polarity chron, and 212.6-251.8 m interval is Gauss normal polarity chron. Integrating the magnetostratigraphy, lithostratigraphic properties and ¹⁴C ages, we divided the Quaternary strata into the Lower Pleistocene, Middle Pleistocene, and Upper Pleistocene series, with depths of 210.9 m, 145.3 m and 24.05 m, respectively.