漳河山前冲洪积扇BK02孔古地磁定量分析及第四纪地层划分

Paleomagnetic Quantitative Analysis and Quaternary Stratigraphic Division of Borehole BK02 in the Front Alluvial Fan of Zhanghe

冀西南平原西缘广泛发育的山前漳河冲洪积扇磁性地层研究尚不完善,其岩性组合特征、沉积环境与平原区建组剖面存在较大差异,第四纪地层精细化划分对比未充分建立。文章通过对位于漳河冲洪积扇西缘的第四纪标准钻孔BK02的岩心观察,根据沉积物颜色、沉积环境、岩性组合、沉积构造及旋回特征,将其第四纪地层松散沉积物划分为了T1~T6六个岩性段。通过对该孔第四纪沉积物地磁极性倒转序列分析,并结合14C、光释光等年代学测量成果,建立了该孔第四纪年代学框架,确定下更新统底界埋深为201.60 m,中更新统底界埋深为97.34 m,上更新统底界暂定为39.86 m,全新统底界埋深为13.75 m。

The study on the magnetic stratigraphy of the Zhanghe alluvial fan in the piedmont of the west margin of the Southwest Plain of Hebei province is not in place,the fine division and correlation of Quaternary strata have not been established sufficiently.Based on the core observation of Quaternary standard borehole BK02,which is located in the western margin of the alluvial fan of Zhanghe River,according to the characteristics of sedimentary color,sedimentary environment,lithologic assemblage,sedimentary structure and cycle,the quaternary unconsolidated sediments can be divided into six lithologic sections T1~T6.Based on the analysis of the sequence of geomagnetic polarity reversal of quaternary sediments in the hole and the results of 14 C and optical luminescence dating,a Quaternary chronological framework of the hole has been established,the depth of the lower Pleistocene,Middle Pleistocene,Upper Pleistocene and Holocene are determined to be 201.60 m,97.34 m,39.86 m and 13.75 m respectively.