Table2_Hints on the Late Miocene Evolution of the Tonale-Adamello-Brenta Region (Alps, Italy) Based on Allochtonous Sediments From Raponzolo Cave.XLSX

Raponzolo is a paleo-phreatic cave explored in 2011 in the Brenta Dolomites (Trentino, Italy), at the remarkable altitude of 2,560 m a.s.l. Differently to all other caves of the area, it hosts well-cemented fine to medium sands of granitic-metamorphic composition. The composition suggests a sediment source from the Adamello and Tonale Unit, separated from the Brenta by one of the most important tectonic lineaments of the Alps (Giudicarie Line). The fine-sand sediment was sampled to determine burial time and thus a minimum age of the cave. Cosmogenic isotopes (26Al and 10Be) in quartz grains allowed to estimate a minimum burial age of 5.25 Ma based on the mean sediment transport time at the surface and infer original altitude of the catchment area. Detrital apatite fission-track (AFT) and U-Pb dating on zircons provide information on the source, both from a regional and altitude (exhumation) perspective. Two populations of detrital AFT ages center at 17 (−2.3 + 2.6) Ma and 23 (−3.3 + 3.9) Ma, whereas the main detrital zircon U-Pb age populations are younger than 40 Ma. These correspond to intrusive and metamorphic sources nowadays outcropping exclusively above 2,200–2,300 m a.s.l. in Northern Adamello and Tonale. The results point to a late Miocene erosion and infilling of the cave by allochtonous sediments, with important implications on the timing of cave speleogenesis, as well as the paleogeographical connection, tectonic evolution and uplift of different structural units of the Alps. The roundness and the well sorted size of the quartz grains suggest a fluvial or aeolian origin, possibly recycled by glacial activity related to cold events reported in high latitude areas of the world at 5.75 and 5.51 Ma. These glacial phases have never been documented before in the Alps. This information confirms that the valleys dividing these geological units were not yet deeply entrenched during the onset of the Messinian Salinity Crisis (5.6–5.5 Ma), allowing an efficient transport of sediments across major tectonic lineaments of the Alps. This study shows the potential of cave sediments to provide information not only on the age of speleogenesis but also on the paleogeography of a wide area of the Alps during the late Miocene.

Raponzolo，位于意大利特伦蒂诺自治区的布伦塔多洛米蒂山脉（海拔2,560米），是一座在2011年进行考察的古老岩溶洞穴。与其他地区的洞穴不同，该洞穴内藏有由花岗岩变质岩组成的细至中粒级紧密胶结的沙质沉积物。其成分表明，沉积物来源于亚当埃尔和托纳莱单元，该单元与布伦塔之间的距离由阿尔卑斯山脉最重要的构造线之一（Giudicarie线）所分隔。通过对细沙沉积物的采样，研究人员确定了埋藏时间，从而确定了洞穴的最小年龄。石英颗粒中的宇宙成因同位素（26Al和10Be）的测定，基于地表的平均沉积物搬运时间，估计了至少5.25百万年的埋藏年龄，并推断出集水区的原始海拔。碎屑磷灰石裂变径迹（AFT）和锆石的U-Pb定年提供了关于源区信息，从区域和海拔（抬升）的角度进行分析。碎屑AFT年龄的两个群体分别集中在1.7（-2.3 + 2.6）百万年和2.3（-3.3 + 3.9）百万年，而主要的碎屑锆石U-Pb年龄群体则小于40百万年。这些年龄对应于现在仅在北部亚当埃尔和托纳莱海拔2,200至2,300米以上出露的侵入岩和变质岩源区。这些结果指向了上新世晚期的侵蚀和异源沉积物填充洞穴，这对洞穴形成时间、古地理联系、构造演化以及阿尔卑斯山脉不同构造单元的抬升具有重大意义。石英颗粒的圆度和良好的分选性表明，其可能具有河流或风成起源，并可能被与全球高纬度地区在5.75和5.51百万年前报道的冷事件相关的冰川活动所循环利用。这些冰川期在阿尔卑斯山脉中尚未被记录。这些信息证实，在墨西拿盐度危机（5.6至5.5百万年前）开始时，分隔这些地质单元的河谷尚未形成深谷，这允许沉积物在阿尔卑斯山脉的主要构造线上有效搬运。这项研究显示了洞穴沉积物在提供洞穴形成年龄信息的同时，还能够揭示阿尔卑斯山脉广大区域在晚中新世的古地理信息。