The catastrophic Vajont landslide that occurred on 9 October 1963 caused about 2000 deaths when 270–300 Mm³ of rock and debris slid from the northern slope of Mt. Toc into the newly created artificial reservoir, displacing some huge water waves that flooded the nearby villages. The 1963 slide was an en-block remobilisation of a prehistoric rockslide lying on the southern reservoir bank. Basal sliding took place within a complex lithostratigraphic sequence of cherty–marly limestones and clay interbeds belonging to the Fonzaso Formation of Upper Jurassic age. In this work, we investigate the geological origin and provenance of the Vajont clays according to the results of mineralogical and geochemical analyses performed on several clay samples which were collected from the landslide failure surface and the same limestone sequence in the surrounding area. The sampled clayey materials contained variable amounts of clay minerals (36–96%), calcite (4–64%) and quartz (0–6%). The dominant clay minerals were illite/smectite (I/S) mixed layers with a high illite content (85–50%), which was consistent with the high percentage of K₂O (1.17–5.77%). The Vajont clays included in the Fonzaso Fm. can be referred to as K-bentonites and can be interpreted as distinct deposits of volcanoclastic materials (tephra), representing the sedimentary inputs of volcanic ashes that interrupted the “normal” calcareous sedimentation during the late Oxfordian–upper Tithonian (158–145 Ma). The soft clay interbeds played a different mechanical role in the occurrence of the prehistoric rockslide and the 1963 en-block remobilisation. When referring to the ancient slope failures, distinct clay-rich layers that were concentrated within some specific lithostratigraphic intervals of the Jurassic cherty limestone sequence caused a localised decrease in the available shear strength, allowing for relative shear displacements along the dip-slope bedding planes. This caused additional shear/tensile fracturing of limestone beds and the formation of a stepped basal failure surface. During the 1963 remobilisation, the clay layers contributed to the average shear strength decrease of the debris material forming the basal shear zone of the slide, but the main triggering factor was the increase in pore pressures caused by the reservoir-induced groundwater inflow.

1963 年 10 月 9 日发生的灾难性 Vajont 滑坡在 270-300 毫米³时造成约 2000 人死亡大量的岩石和碎屑从托克山北坡滑入新建的人工水库，取代了一些淹没附近村庄的巨大水浪。1963 年的滑坡是对位于南部水库岸边的史前岩石滑坡的整体再动员。基底滑动发生在属于上侏罗纪丰扎索组的燧石-马里灰岩和粘土夹层的复杂岩石地层序列中。在这项工作中，我们根据对从滑坡破坏面和周边地区相同石灰岩序列收集的几个粘土样品进行的矿物学和地球化学分析结果，调查了 Vajont 粘土的地质成因和来源。采样的粘土材料含有不同数量的粘土矿物（36-96%），方解石 (4–64%) 和石英 (0–6%)。主要粘土矿物为伊利石/蒙脱石（I/S）混合层，伊利石含量高（85-50%），这与高比例的钾相一致₂O (1.17–5.77%)。Fonzaso Fm 中包含的 Vajont 粘土。可以被称为钾膨润土，可以解释为火山碎屑物质（tephra）的独特沉积物，代表了在牛津阶晚期 - 上提通阶（158-145 Ma）期间中断“正常”钙质沉积的火山灰沉积输入. 软粘土夹层在史前滑坡的发生和 1963 年的整体再动员中发挥了不同的机械作用。当提到古老的斜坡破坏时，集中在侏罗纪燧石石灰岩层序的某些特定岩石地层间隔内的不同富粘土层导致可用剪切强度局部降低，从而允许沿倾角层理面发生相对剪切位移。这导致了石灰岩床的额外剪切/拉伸破裂和阶梯状基底破坏面的形成。在 1963 年的再活动期间，粘土层导致形成滑坡基底剪切带的碎屑材料的平均剪切强度降低，但主要触发因素是由水库引起的地下水流入引起的孔隙压力增加。