福建三明地区第四纪地层序列

    Quaternary stratigraphic sequence in Sanming area Fujian Province

    • 摘要: 为解决福建三明地区第四纪岩石地层划分方案未统一、年代地层研究精度偏低和区域河流阶地序列研究程度较低的问题, 对该区的第四系进行了系统的综合地层学研究。根据岩石地层学研究, 结合光释光测年结果和地貌地层学特征, 将三明地区的第四系划分为3个岩石地层单位。由老到新为: 同安组, 一般组成三至五级河流阶地, 局部地区表现为山前洪积扇, 沉积物以褐红色为主, 由上部细粒沉积物和下部泥质网纹化砾石层组成二元结构, 时代为中更新世—晚更新世早期; 龙海组, 一般组成二级阶地或山前洪积扇, 少数为一级阶地下部, 沉积物以褐黄色为主, 由上部细粒沉积物或细网纹红土和下部泥质砂砾石层组成二元结构, 时代为晚更新世; 小陶组, 组成一级阶地及漫滩, 沉积物以灰黄色、灰褐色为主, 由上部细粒沉积物和下部砂砾石层组成二元结构, 局部存在淤泥质透镜体, 时代为全新世。在此基础上, 建立了沙溪、巴溪和文川溪的河流阶地序列, 以期更加全面地了解区内第四纪地层格架。

       

      Abstract: In this study, we systematically studied Quaternary stratigraphic sequence of Sanming area, Fujian Province, to address several debated topics, including inconsistent division of Quaternary, imprecise chrono-stratigraphy and poor-studied river terraces. On the basis of intensive field surveys, the lithostratigraphy, optically stimulated luminescence (OSL) dating results and morphostratigraphic characteristic, the Quaternary deposits in Sanming area have been divided into three units: the Tong'an Formation, Longhai Formation and Xiaotao Formation. The Tong'an Formation, formed from Middle Pleistocene to early Late Pleistocene, consists of dark red sediments, which are fine grained in the upper part and argillaceous net-like gravels in the lower part, comprising terraces T3, T4, T5 and local alluvial fan. The Late Pleistocene Longhai Formation is divided into two parts: fine-grained or thin red earth in the upper part, and argillaceous sandy gravels in the lower part. The sediment's color shows brownish yellow to this formation. Most of the Longhai Formation comprise terrace T2 and alluvial fan, few bottom of terrace T1. The Holocene Xiaotao Formation is composed of grayish yellow and brownish gray sediments, which are fine grained in the upper part and sandy gravels in the lower part, comprising terrace T1 and flood plain. Moreover, terrace sequences of Sha River, Ba River and Wenchuan River have been established in order to comprehensively understand the Quaternary deposits in the study area.

       

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