The Opalinus Clay is notable in Switzerland as being the selected host rock for deep geological disposal of radioactive waste. Since the early 1990’s, this argillaceous mudstone formation of Jurassic age has been intensively studied within the framework of national and international projects to characterize its geological, hydrological, mechanical, thermal, chemical, and biological properties. While there is no formal stratigraphic subdivision, the Opalinus Clay lithology is classically divided into several, dam- to m-scale sub-units (or facies), depending on location. Recent multi-proxy studies (combining petrographic, petrophysical, geochemical and mineralogical analyses) have however demonstrated that high, intra-facies, lithological heterogeneity occurs at the dm- to cm-scale. To constrain this small-scale heterogeneity into distinct lithological units (subfacies), the present study aims at defining and presenting a convenient subfacies classification scheme covering the overall Opalinus Clay lithology across northern Switzerland. Petrographic (macro- and microfacies), mineralogical (X-ray diffraction) and textural (image analysis, machine learning and 3D X-ray computed tomography) analyses are performed on diverse drill cores from the Mont Terri rock laboratory (northwestern Switzerland), and results are extended further to the east (Riniken, Weiach and Benken). Most of the investigated Opalinus Clay can be described by the use of five distinctive subfacies types (SF1 to SF5), which are visually and quantitatively distinguishable by texture (grain size, bedding, fabric and color) and composition (nature and mineralogy of components). The five subfacies types can be further refined by additional attributes and sedimentary characteristics (biogenic, diagenetic and structural). Eventually, the widespread and consistent use of standardized Opalinus Clay subfacies types provides the means to harmonize petrographic descriptions within multidisciplinary research projects, enhance reproducibility of in-situ experiments, and further evidence the tight relations between lithology and various rock properties.

中文翻译：

---

定量分析Opalinus粘土中的岩性非均质性：使用新型自动核心图像识别工具实现统一的亚相分类方案

Opalinus粘土在瑞士是著名的，是放射性废物深层地质处置的选定寄主岩石。自1990年代初以来，已在国家和国际项目的框架内对侏罗纪时代的泥质泥质岩层进行了深入研究，以表征其地质，水文，机械，热，化学和生物学特性。尽管没有正式的地层细分，但Opalinus粘土岩性根据位置划分为几个达姆级至m级的子单元（或相）。然而，最近的多代理研究（结合岩石学，岩石物理，地球化学和矿物学分析）表明，在dm-cm范围内发生了高的相内岩性非均质性。为了将这种小规模的非均质性限制在不同的岩性单元（亚相）中，本研究旨在定义并提出一种便捷的亚相分类方案，该方案涵盖了瑞士北部的整个Opalinus粘土岩性。岩石学（宏观和微相），矿物学（X射线衍射）和纹理学（图像分析，机器学习和3D X射线计算机断层扫描）分析是在蒙特里岩石实验室（瑞士西北部）的各种钻芯上进行的，并且结果进一步扩展到东部（Riniken，Weiach和Benken）。可以使用五种不同的亚相类型（SF1至SF5）来描述大多数被研究的Opalinus粘土，它们在视觉和数量上都可以通过质地（粒度，铺垫，织物和颜色）和组成（成分的性质和矿物学）。可以通过其他属性和沉积特征（生物成因，成岩作用和构造作用）进一步细化这五个亚相类型。最终，标准化和稳定的欧泊林粘土亚相类型的广泛使用为协调多学科研究项目中的岩相描述，增强原位实验的可重复性以及进一步证明岩性与各种岩石性质之间的紧密联系提供了手段。