鲁北平原南部QK4钻孔岩心特征及第四纪地层划分

    Core characteristics and Quaternary stratigraphic division of borehole QK4 in southern Lubei Plain

    • 摘要: 第四纪地层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,区域上晚更新世以来的地层已被广泛研究,但对完整的第四纪地层格架研究不足。为此,对鲁北平原QK4钻孔(深度285.98 m)进行了古地磁、AMS 14C、OSL、测井、岩石地层等研究。在系统的古地磁采集(398件)、处理和测试的基础上,认为岩心记录了布容正极性时(Brunhes)、松山负极性时(Matuyama)、高斯正极性时(Gauss)及其中的部分极性亚时。在磁性年代框架的基础上,结合AMS 14C、OSL、测井及岩石地层特征,对钻孔揭露的第四纪地层进行了划分,确定了全新统、上更新统、中更新统、下更新统的底界分别位于4.11、23.49、118.70、147.35 m,钻孔揭露的地层从上向下依次为新生界黑土湖组、大站组、平原组和明化镇组。研究结果建立了鲁北平原南部第四纪地层格架,为该区第四纪地层划分对比、古地理环境演化等提供了可靠的岩石学、年代学、古地磁学证据。

       

      Abstract: The establishment of the Quaternary stratigraphic framework is of great significance for the study of regional stratigraphic correlation and paleogeographic environment evolution. The sedimentary strata since the Late Pleistocene have been extensively studied, but the research on the complete Quaternary stratigraphic framework is not yet sufficient. Therefore, paleomagnetic, AMS 14C, OSL, well logging, and lithostratigraphic studies were conducted on borehole QK4 (depth: 285.98 m) in the Lubei Plain. Based on the systematic paleomagnetic sampling (398 samples), processing, and testing, it is considered that the cores from borehole QK4 recorded Brunhes normal polarity chron, Maruyama reversed polarity chron, Gauss normal polarity chron, and some of their polarity subchrons. Based on the magnetic age framework, as well as MS 14C, OSL, well logging, and lithostratigraphic characteristics, the Quaternary strata revealed by borehole QK4 were divided, and it was determined that the bottom boundaries of the Holocene, Upper Pleistocene, Middle Pleistocene, and Lower Pleistocene strata have depths of 4.11 m, 23.49 m, 118.70 m, and 147.35 m, respectively. Moreover, as the strata revealed, the strata revealed by borehole QK4 include the Cenozoic Heituhu, Dazhan, Pingyuan, and Minghuazhen formations from top to bottom. The results allowed for the establishment of the Quaternary stratigraphic framework in the southern Lubei Plain, thus providing reliable petrological, chronological, and paleomagnetic evidence for the Quaternary stratigraphic division and correlation and palaeogeographic environmental evolution in the southern Lubei Plain.

       

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