Magma-poor ocean-continent transitions at distal rifted margins record complex stratigraphic interactions engendered by extreme crustal thinning and mantle exhumation. The Tasna ocean-continent transition, exposed in the Middle Penninic Tasna nappe in eastern Switzerland, is so far the only known example where the lateral transition from continental crust to exhumed serpentinized mantle lithosphere is exposed and not overprinted by later Alpine deformation. This paper presents sedimentological, structural, and petrographical observations and detrital zircon provenance data to document: (1) the processes controlling continental hyperextension and mantle exhumation; and (2) the facies, depositional systems, sediment sources, delivery pathways, and depositional stacking patterns associated with magma-poor ocean-continent transitions. Our results show that the basement units of the Tasna ocean-continent transition are composed of prerift upper and lower crust and subcontinental mantle rocks juxtaposed as part of the continental crustal thinning process. The absence of pervasive, synrift deformation in the lower-crustal rocks indicates that the thinning was likely achieved by deformation along localized shear zones before being exhumed at the seafloor by brittle, late extensional detachment faulting and not by any form of lower-crustal flow.The age of the first sediments deposited on the continental crust and exhumed mantle, the so-called Tonschiefer Formation, is considered to be Late Jurassic. A key observation is that the restored morpho-tectonic and sedimentary evolution of the Tasna ocean-continent transition shows the intercalation of downdip, transported platform-derived sediments and along-axis–derived siliciclastic sediments originating from the recycling of prerift sediments, local basement, and/or extra-Alpine sources.

中文翻译：

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化石-陆-陆过渡的构造沉积沉积：塔斯纳纳普，阿尔卑斯山中部（瑞士东南部）

远端裂谷边缘的岩浆贫瘠的海陆过渡记录了地壳的极薄化和地幔掘出引起的复杂地层相互作用。塔斯纳海陆过渡带暴露于瑞士东部的中Penninic塔斯纳中部，是迄今为止唯一已知的例子，从大陆壳到发掘出蛇形化的地幔岩石圈的横向过渡被暴露，并且不会因后来的高山变形而被覆盖。本文介绍了沉积学，结构和岩石学的观测资料以及碎屑锆石的来源资料，以证明：（1）控制大陆过度扩张和地幔掘出的过程；（2）与岩浆稀少的海洋—大陆过渡有关的相，沉积系统，沉积物来源，输送途径和沉积堆积模式。我们的研究结果表明，塔斯纳海陆过渡带的基底单元是由前裂谷的上，下地壳和次大陆幔岩石并列组成的，这是大陆地壳变薄过程的一部分。下地壳岩石中没有普遍的，同理的形变，表明变薄很可能是通过沿局部剪切带的变形实现的，然后才被海底的脆性，晚期伸展性剥离断层掘出，而不是通过任何形式的下地壳流动。沉积在大陆壳和发掘出的地幔上的第一批沉积物的年龄，即所谓的Tonschiefer组，被认为是侏罗纪晚期。一项重要的观察结果是，塔斯纳海-陆过渡带的形态构造和沉积演化得以恢复，显示出下倾插层，