METHODOLOGY FOR COMPILATION OF OFFSHORE GEOLOGICAL MAP AND ITS SPECIALITIES
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摘要: 在执行海洋地质保障工程"1:500万中国海陆系列图-地质图"编图项目的过程中,研究并采用了较为新颖的海域地质内容编图方法,其中关键的技术是如何用叠置方法和透视方法表示海区被掩盖的地质体。叠置法无疑是按正常沉积序列表示地层的叠置关系;透视法的关键步骤就是将叠置在新近系之下的地质体透视到图面上。此方法可归纳为块、线、面三层透视,即被掩盖的中生界、浅层侵入岩或前古生代地壳以"块"的形式透视,其上叠置的古近系则以"线"的形式透视,线叠置在块之上,最上层的新近系以"面"表示。当然,有透视内容的区域此新近系"面"视为透明。对照20世纪80年代以来前人编制海域地质图的一些做法及其优缺点,此编制方法明显优于其他方法。有望今后在国内外海洋地质调查和研究部门进一步推广使用。Abstract: A new method for offshore geological map compilation is introduced in this paper. For offshore mapping, the key problem is how to map the covered geological objects on geological maps. We proposed a method characterized by the combination of superposition and transparency. Superposition means that the map must be able to show the normal stratigraphic sequences, and the transparency means that it must be able to project the buried strata, igneous and other geological bodies covered by the Neogene on to the map. There are three ways to project the covered geological phenomena onto the map, namely, block, line and surface. According to the principles of transparency, the covered Mesozoic sedimentary strata, shallow basalt or acid intrusions and/or Precambrian rocks are shown on geological maps as blokes, while the boundaries of the Paleogene strata overlapping on these blocks are shown as lines. Lastly, the Neogene are shown on maps as surface and this surface is "transparent". One can see the older geological objects mentioned above through it.The method evidently has advantage to map the superimposed geological bodies in such offshore areas as the South China Sea. It is expected to be used by other mapping programs.
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Key words:
- geological map /
- offshore geological map compilation /
- superimposition /
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