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| 基金项目：国家自然科学基金项目（41672048），中国地震局地质研究所地震动力学国家重点实验室项目（LED2016B01），余姚四明山地质公园科研项目“四明山古夷平面地质地貌研究” |
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| 摘要： |
| 古夷平面研究在地貌演化和新构造运动研究中占有极其重要的地位，但由于遭受构造运动和剥蚀作用的影响，很多古夷平面遗迹已无从清晰辨识。浙江四明山顶古近纪夷平古风化壳面的发现，为研究浙江东部甚至华东地区的新生代地貌演化提供了重要地质信息，同时为始新世和中新世时的古气候、古环境研究提供了重要物质证据。通过详细的野外地质调查，系统采集了该区5个点位的20个古风化壳样品和7个点位的15个现代风化壳样品，开展黏土矿物分析和玄武岩K-Ar年龄测试。研究确认四明山地区发育有2期古夷平面遗迹，即古近纪（E）和新近纪（N）古夷平面遗迹：第一期夷平面发育时间为65.0～32.2 Ma，解体和古夷平面遗迹保存时间为32.2～21.7 Ma；第二期夷平面发育时间为21.7～10.5 Ma，解体和古夷平面遗迹保存时间为10.5～3.0 Ma。研究区2期火山活动喷发所形成的玄武岩盖层有效保护了该区的古风化壳，从而使四明山古夷平面遗迹具有空间展布完整、剖面信息清晰等特征，呈现出由古夷平面（古风化壳）与玄武岩堆积面（现代风化壳）组成的“双风化壳”现象，为观察古夷平面遗迹特征提供了最佳场所。 |
| 关键词：古近纪（E）古夷平面 新近纪（N）古夷平面 玄武岩盖层 双风化壳剖面 浙江四明山 |
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| Abstract: |
| Ancient planation surface plays an important role in the research of geomorphological evolution and neotectonics. However, many ancient planation surfaces are hard to be identified due to the influence of tectonics and erosion. The Paleogene planation surface at the top of Siming Mountain reveals important geological information on the Cenozoic geomorphological evolution of eastern Zhejiang or even East China, as well as important evidence for the research of the paleoclimate and paleoenvironment during the Eocene and Miocene. Based on detailed field investigation, this work collected 20 ancient planation surface samples from 5 sites and 15 modern planation surface samples at 7 sites to conduct clay mineral analysis and K-Ar dating of basalt. It confirms that there are two stages of ancient planation surfaces in this area, which were formed in the Paleogene (E) and Neogene (N), respectively. The first stage of planation surface was developed during 65.0-32.2 Ma, and disintegrated and preserved during 32.2-21.7 Ma; the second stage of planation surface was developed during 21.7-10.5 Ma and disintegrated and preserved at 10.5-3.0 Ma. The overlying basalt layers, formed during the 2 volcanic activities, have effectively protected the ancient weathered crusts, such that the relics of ancient planation surfaces have a complete spatial distribution and clear section information. The double weathered crusts, composed of ancient planation surface (ancient weathered crust) and basalt layers (modern weathered crust), become a perfect site for studying the relics of ancient planation surface. |
| Keywords:Paleogene (E) planation surface Neogene (N) planation surface overlying basalt layer double weathered crust section Siming Mountain in Zhejiang Province |
| 郑丽波，戴雪荣，张欢，等.中国东部四明山古夷平面遗迹特征与演化[J].地质学刊,2018,42(4):543-551 |
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