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通过闽西地区永安盆地与崇安盆地下白垩统坂头组凝灰岩夹层中的岩浆锆石定年研究以及古生物研究,首次获得2个盆地坂头组底部开始沉积的准确年龄,分别为(144±2)和(116±2)Ma。根据它们与上覆地层关系来看,2个盆地坂头组顶部年龄基本等时约为100 Ma。因此,崇安盆地坂头组仅相当于永安盆地吉山剖面上段。在与临区地层对比时,建议将永安盆地坂头组与浙西建德群以及上覆的馆头组对比,而崇安盆地下梅剖面的坂头组仅与馆头组对比。此外,通过对2个盆地坂头组火山凝灰岩夹层锆石年龄概率分布特征的研究以及沉积学研究,发现永安盆地和崇安盆地的成盆时间并不一致,分别为(157±3)和(127±2)Ma BP。这可能是导致2个盆地内坂头组不能等时对比的重要原因。通过对2个坂头组典型剖面的深入剖析表明虽然晚中生代以来,华南沿海地区均处于伸展拉张背景,各盆地演化过程大体相似,盆内地层结构与层序也基本相同,但由于不同地区拉张成盆地的具体时间并不一致,导致不同盆地间相似地层并不到处等时。在区域地层对比过程中必须予以重视。
Through the zircon magmatic dating and the paleontological study in the tuff intercalations of the Lower Cretaceous Bantou formation in the Yong’an basin and the Chong’an basin in western Fujian, the exact ages of the bottom sediments of the Bantou Formation in the two basins were obtained for the first time (144 ± 2 ) And (116 ± 2) Ma. Based on their relationship with the overlying strata, the top of the Bantou Formation in the two basins has a basic equivalent time of about 100 Ma. Therefore, the Sakamoto Group in Chongan Basin is only equivalent to the upper section of Jishan Section in Yong’an Basin. In comparison with the adjacent strata, it is suggested that the Bantou Formation in Yong’an Basin be compared with the Jiande Group in the western Zhejiang Province and the overlying Tingtou Formation, whereas the Bantian Formation at Xiamei Section in the Chong’an Basin is only contrasted with the Guantou Formation. In addition, by studying the age distribution of volcanic tuff intercalations and the sedimentary study of the volcanic tuff in the two basins, it is found that the basin forming time in Yong’an and Chong’an basins is not consistent with that of (157 ± 3) and (127 ± 2) Ma BP. This may be an important reason for the inability of Isabela group in two basins to be compared. Through in-depth analysis of two typical sections of Bantou Formation, it shows that although the coastal areas in South China are in extensional and extensional background since the Late Mesozoic, and the evolution processes of the basins are generally similar, the stratigraphic structure and sequence in the basin are basically the same. However, due to the different regions The specific time to pull into the basin is not consistent, resulting in similar strata between different basins are not everywhere. In the process of stratigraphic comparison, attention must be paid.