Table3_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（拉波佐洛）乃一处史前潜穴，位于2011年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），其地质特征引人注目。与其他区域的所有洞穴不同，它拥有由花岗岩-变质岩组成的致密细至中粒沙。该成分表明沉积物源自亚当洛和托纳莱单元，与布伦塔之间相隔阿尔卑斯山脉最重要的构造线之一（Giudicarie线）。对该细沙沉积物进行采样，以确定埋藏时间，从而确定洞穴的最小年龄。石英颗粒中的宇宙成因同位素（26Al和10Be）使得基于地表平均沉积物运输时间，估算出最小埋藏年龄为5.25百万年，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年代测定提供了关于源头的区域和高度（抬升）方面的信息。碎屑AFT年龄的两个种群分别集中在17（-2.3 + 2.6）百万年和23（-3.3 + 3.9）百万年，而主要的碎屑锆石U-Pb年龄种群则年轻于40百万年。这些对应于如今仅在北部亚当洛和托纳莱海拔2,200至2,300米以上出露的侵入性和变质岩源。这些结果指向了上新世晚期的侵蚀和外来沉积物填充洞穴，对洞穴洞穴形成的时间、古地理联系、构造演化和阿尔卑斯山脉不同结构单元的抬升具有重要意义。石英颗粒的圆润度和良好的粒度排序表明其具有河流或风成的起源，可能受到与5.75和5.51百万年前世界高纬度地区报道的冷事件相关的冰川活动的再循环。这些冰川阶段在阿尔卑斯山脉中前所未有。这些信息证实，在梅辛尼亚盐度危机（5.6-5.5百万年前）开始时，分隔这些地质单元的山谷尚未深深下陷，允许沉积物在阿尔卑斯山脉的主要构造线之间有效运输。这项研究揭示了洞穴沉积物提供的信息潜力，不仅包括洞穴形成的年龄，还包括上新世晚期阿尔卑斯山脉广大地区的古地理。