Raponzolo Cave opens at 2,560 m asl (46°11′55.1″N, 10°54′40.7″E), on the steep eastern flank of Cima Grosté (2,898 m a.s.l.), toward the upper end of the Tovel Valley, the widest valley of the Brenta Massif (3.5 km of width, Figure 2). The cave is a single sub-horizontal tunnel about 180 m long, excavated in the Dolomia Principale formation. An initial W-trending ascending gallery paved with loose dolomitic sand is followed by a N-trending descending gallery partially filled with cemented medium-fine siliciclastic sand (Figures 3, 4). Comparable sediments are not found anywhere else in the area. The sediments are present on the gallery floor as well as on walls and roofs, suggesting that the whole conduit was once filled (and then re-excavated). The cave presents typical phreatic morphologies with large scallops up to 0.5 m in diameter, without traces of vadose morphologies (Figure 3B).

The analyses targeted pristine and well cemented sediment samples from Raponzolo Cave. A multi-technique approach was used to obtain information about composition, provenance and burial time. These included: petrographic observation using an optical microscope, X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), ²⁶Al and ¹⁰Be cosmogenic isotopes, Apatite Fission Track (AFT) analyses and U-Pb dating on zircons.

Petrographic observations were accomplished on three thin sections (∼25 μm) with a LEICA Stereomicroscope and an OLYMPUS BX-41 optical microscope. Images have been obtained using a OLYMPUS COLOR VIEW II-SET camera and processed through OLYMPUS C-VIEW II-BUND-cell^B software. For grainsize measurements, 300 g of sample have been treated with a 70% acetic acid solution in order to dissolve the carbonate cement and release the insoluble fraction for grain size measurements through sieves. Pre- and post-dissolution weighing ascertained the cement/sediment ratio. Grainsize measurement utilized standard ASTM sieves 25, 40, 70, 100, 200, 230 and >230, with meshes corresponding to 0.71, 0.425, 0.212, 0.15, 0.075, 0.063 and <0.063 mm, respectively. Analyses were accomplished at Bologna University (Italy).

The sample was ground to ultrafine powders and kept 24 h at 110°C. Ten grams of sample were mixed with 2.5–5 ml of Elvacite polymer resin, dissolved in acetone. The mixture was stirred to allow acetone evaporation and Elvacite distribution. The resultant powder was placed in a penny-shaped mold and compressed with a vertical pressure of 40 MPa for 1 min. A WD-XRF Axios–Panalytical spectrometer equipped with five diffraction crystals was used for the analyses. The SuperQ software package provided by Panalytical was employed for calibration and data reduction. Calibration is based on 30 certified international standards. The precision of analyzed elemental abundances is better than ± 0.2% for SiO₂, and ± 0.1% for the other major elements except for MnO₂ and P₂O₅ that have concentration errors of approximately ± 0.02%. For trace elements, relative errors are up to 10% for concentrations of 10–100 ppm, better than 5% for higher concentrations and reaching ∼50% at levels below 10 ppm. Therefore, the detection limit is approximately 5–10 ppm.

The mineralogical composition was investigated by a Philips PW3710 X-Ray diffractometer (current: 20 mA, voltage: 40 kV, range 2θ: 5–80°, step size: 0.02° 2θ, time per step: 2 s) operating at the University of Genua (Italy), which mounted a Co-anode. Acquisition and processing of data was carried out using the Philips High Score software package.

The burial age method involves the measurement of two isotopes (²⁶Al and ¹⁰Be) that are produced by cosmic radiation in quartz near the surface prior to burial. ²⁶Al and ¹⁰Be accumulate at a ratio of about 6.8:1 (Balco et al., 2013) in quartz grains, with a rate of a few atoms per Gram of quartz per year. Sufficiently deep burial (more than 10 m) of such quartz-rich sediments in a cave assures shielding from further cosmic rays. After burial, the ²⁶Al and ¹⁰Be concentrations in the sample are only affected by their relative decay resulting in a decrease in the ²⁶Al/¹⁰Be ratio. This ratio can be used to derive a burial age (Gosse and Phillips, 2001; Granger, 2006). A prerequisite of the burial dating technique is that samples have been exposed long enough to cosmic rays and accumulated sufficient cosmogenic nuclides prior to burial. The upper limit for measurement of the ²⁶Al and ¹⁰Be isotope pair is between 5 and 6 Ma depending on the accumulated cosmogenic isotopes during surface exposure (Häuselmann et al., 2020).

The isotope concentrations can also be used to infer paleo-erosion rates of the source area prior to burial of the clasts. This is accomplished by backward modeling the quantity of nuclides present prior to the burial coupled with local production rate estimates. The pre-burial ²⁶Al/¹⁰Be ratio (∼6.8:1) is basically not influenced by production rate and thus elevation (Nishiizumi et al., 1989; Stock et al., 2005a) and therefore burial ages remain unaffected by altitude changes in the source area.

The sediment sample was broken into smaller pieces and decarbonated using HCl; due to many accessory minerals, only 38.0062 g of pure quartz could be recovered. Quartz was sieved and the fraction between 250 and 710 µm was physically concentrated (separation by form, magnet- and reverse magnet separation and heavy liquid) and then cleaned with HF-HNO₃ to remove intergrown feldspars to obtain a clean quartz concentrate. This concentrate was dissolved and cleaned by dissolution, precipitation, and ion exchange. ²⁶Al and ¹⁰Be were separated, precipitated, oxidized, and measured on an AMS (in Purdue University). Chemical blanks were also measured to subtract laboratory influence. The AMS measures the ¹⁰Be/⁹Be ratio and the ²⁶Al/²⁷Al ratio; while ⁹Be is added artificially, ²⁷Al normally abounds in quartz-rich samples.

Fission-tracks in apatite are damage zones in the crystal lattice formed during the radioactive decay of ²³⁸U. At temperatures above 120°C tracks are quickly annealed, whereas at temperatures below 60°C tracks are retained. The temperature range between retention and total annealing is called the partial annealing zone (PAZ). In this range fission tracks progressively narrow and shorten as a function of time and temperature (Naeser, 1979).

Fission-track sample preparation and analysis were performed on 100 apatite grains at ETH Zurich. Mounts of grains were polished and etched in 5.5 N HNO₃ at 21°C for 20 s to reveal spontaneous tracks. Samples were irradiated with thermal neutrons in the reactor at the Radiation Center of Oregon State University with a nominal fluence of 1.2 × 10¹⁶ n/cm². The CN-5 dosimeter was used to measure neutron fluence. After irradiation, induced fission tracks in the external detectors, low U muscovite sheets, were exposed through etching in 40% HF at 21°C for 45 min. AFT ages were calculated using the external-detector and the ζ-calibration methods (Hurford and Green, 1983) with IUGS standards (Durango and Fish Canyon) and a value of 0.5 for the 4p/2p geometry correction factor. The analyses were subjected to the χ² test (Galbraith, 1981) to detect whether the data sets contained any extra-Poissonian age scatter. A χ² probability of 5% denotes that the age distribution contains multiple age populations. AFT age distributions can be decomposed into age populations using kernel density estimate techniques: we used Binomfit by Brandon (1996) that is most suitable to deal with AFT samples with low density of spontaneous tracks.

U-Pb isotope intensities from 431 laser ablation spots in 371 zircon crystals were measured by inductively coupled plasma mass-spectrometry (LA-ICPMS) at ETH Zurich. The ablation areas with a spot diameter of 20 μm were pre-selected with the aid of cathodoluminescence images in order to identify zonations and crystal defects, which were then avoided. Both the core and rim of zircons were measured in the suitable grains.

U and Pb were analyzed using a Resonetic Resolution 155 laser ablation system with a repetition rate of 5 Hz and an energy density of 2 J cm⁻² coupled to a Thermo Element XR Sector-field ICP-MS measuring ²⁰²Hg, ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb, ²³²Th, ²³⁵U, and ²³⁸U intensities (Guillong et al., 2014). GJ-1 (Jackson et al., 2004) was used as primary reference material, and accuracy of the method was confirmed by four secondary standards (AUSZ7-5, OD-3, Temora2, and 91,500). Ages and ratios corrected for instrumental drift and down hole fractionation were obtained using the iolite 2.5 (Paton et al., 2010) and VizualAge software (Petrus and Kamber, 2012). No common Pb correction was applied, since contaminated signals are recognized as discordant ages in the Concordia plots, which were produced with Isoplot 4.1 (Ludwig, 2001). Error ellipses represent 2 s analytical errors of the ²⁰⁷Pb/²³⁵U and ²⁰⁶Pb/²³⁸U ratios, respectively.

The sampled sediment from Raponzolo Cave is a fine (51.6%) to very fine (22.8%) sand with moderate mud (clay + silt) fraction (18.2%); the carbonate cement and very few carbonatic grains, before dissolution, accounted for 54.4% of the original weight (Figure 5). Thin section analyses have shown the presence of both monomineralic and polymineralic grains as following (Figure 6; abundant: widespread in all observations; common: present in all observations; rare: only few grains detected):

• Biotite (abundant) in form of elongated grains with rounded tips casually oriented within the sample.

In addition, a few polymineralic grains are representative of amphibolites, micaschists and gneiss. XRD analysis confirms thin section observations, although it was not able to define the specific amphibole as hornblende due to low lines at the limit of detection for these minerals. The composition of the sample obtained through XRF is reported in Table 1. High Ca content (∼34%) is related to the carbonate cement, while Si from quartz and Al from silicates reach respectively 25 and 9% of the sediment, with a relatively high Fe content (2.4%) (related to biotite and iron hidroxides). p (0.1 %wt, in form of P₂O₅) and Zr (84 ppm) are due to the presence of apatites and zircons. Sub-rounded quartz grains are indication of transport by saltation and traction. Some of these grains show striking rounded morphologies, suggesting recycling through different erosion and transport phases. On the other hand, biotite is abundant and well preserved, with some rounded elongated morphologies related to limited transport by flotation (Garzanti et al., 2011).

The ¹⁰Be/⁹Be ratio is very small (7.8 × 10⁻¹⁵), but in line with the relatively low amount of pure quartz dissolved. Nonetheless, the error of 10% can be considered acceptable for such low values. The measurement of the procedural blanks yielded a¹⁰Be/⁹Be ratio of 3.78 × 10⁻¹⁵ and a²⁶Al/²⁷Al ratio of 6.41 × 10⁻¹⁵. The blanks thus show that the measurements were good and the standards clean. All results were normalized for a¹⁰Be half-life of 1.39 Ma (Chmeleff et al., 2010; Korschinek et al., 2010). The uncertainties represent the analytical error only. The measurement of ²⁶Al/²⁷Al yielded a value (2.78 × 10⁻¹⁵) below that of the blank (6.41 × 10⁻¹⁵). Therefore, there is no detectable ²⁶Al in the sample. The combined absence of ²⁶Al and presence of ¹⁰Be demonstrates that the sediment was indeed once at the surface, but that the burial time was so long that all ²⁶Al decayed because of its shorter mean half-life. Since ²⁶Al is unavailable, the exact age of the sample cannot be given, as the initial concentration of isotopes prior to burial cannot be recalculated. Nonetheless, we can infer a range of possible burial ages based on the expected mean lifetime of the sediment at the surface and isotope production rate at the altitude of the original catchment area. This hypothesis is presented in the discussion (chapter 4.2).

AFT analyses (Supplementary Table S1) shows a distribution of dates between 4.5 ± 2.6 Ma and 56 ± 17 Ma (1σ). Two distinct populations can be identified through standard kernel density estimate techniques (Binomfit by Brandon, 1996; Supplementary Table S2): a minor and younger populations (P1) that includes 28% of the grains and centers at 17.6 (−2,3 + 2.6) Ma and a larger and older one (P2) that includes 72% of the grains and cetners at 23.3 Ma (−3.3 + 3.9) (Figure 7; Supplementary Table S2). The 431 U-Pb dates (Supplementary Table S3) show dates between 30 and >1,000 Ma old, including only two dates older than 1,000 Ma. This wide distribution consists of two main populations, a larger one (91 ± 1%) with dates centered around 35 Ma and a minor one between 270 and 600 Ma (Figure 8). While the first group is directly related to the emplacement of the Adamello batholith, the second is related to zircons from pre-alpine metamorphic rocks such as those of the Tonale Unit and south alpine basement, and/or to igneous zircons of the Adamello batholith with inherited cores.

The petrographic composition of the sediment indicates a source situated mainly in the granitoid bodies of the Adamello Massif and in the metamorphic units of Tonale. Chalcedony is mostly related to the erosion of pseudotachylitic zones in Adamello-Presanella (Pennacchioni et al., 2006) and minor cherts eroded from the carbonatic sequence of Brenta. Metamorphic clasts (amphibolite) and minerals (especially kyanite) indicate a provenance from the Tonale Unit, which is characterized by high-P mineral suites (Davide et al., 2000).

AFT analysis provides additional indications on the source region (Figure 9). In the Tonale Unit, AFT dates vary between 6 and 25 Ma, and in the Adamello batholith between 8.3 and 23 Ma (Martin et al., 1998; Viola et al., 2003; Reverman et al., 2012). In both regions, AFT dates generally increase with elevation; although the AFT age-elevation relationships vary in age range and slope in different localities and in a few places they are disturbed by tectonic displacements. In the sediments from Raponzolo Cave, the largest fraction (72%) of the detrital AFT dates centers at 23.3 Ma and the remaining fraction (28%) at 17.6 Ma. Thus, the largest fraction of the detrital apatites (red area in Figure 9) comes from the highest portions of the Tonale Unit and/or Adamello complex, at elevations above 2,300 m a.s.l, at present time. Regarding the smaller fraction at 17.6 Ma (blue area in Figure 9), while for Tonale the altitude range of the source region is also above the present elevation of 2,300 m a.s.l., for Adamello it is more difficult to constrain the altitude limit due to different profile distributions depending on the transect location (Figure 9). To solve this uncertainty, another indication is provided by zircon U-Pb ages. Zircon U-Pb ages are related to the crystallization of the magma source, which is not synchronous in all areas of the Adamello. It is thus possible to better understand which part of the batholith the sediment was eroded from if specific age groups are dominant in the cave sediment. While the older zircon age group (Figure 9) is related to recycling of crystals from the Permian basement and crustal rocks within the batholith (Hansmann and Oberli, 1991), the younger peak at 35 Ma indicates that the sediment source was mainly situated in the northern sectors of the Adamello batholith (Adamello North, Genova Valley, Figures 9, 10), as shown by previous U-Pb, K-Ar, and Rb/Sr dating from different areas (Del Moro et al., 1983; Schaltegger et al., 2019). Very few zircons in the dataset (<10) are between 40–42 Ma indicating a negligible contribution from the southern area of the batholith (Daone, Rendena Valley; Figures 9, 10; Schoene et al., 2012). This information allows to define the source region of the sediment in the northern sector of Adamello where AFT ages around 17.6 are also above 2,200–2,300 m a.s.l. at present time.

Therefore, the erosional phase producing the sediment filling Raponzolo cave occurred when the present valley network was not as deeply entrenched as today, and younger thermochronological units where not yet exposed in the source region.

Due to the lack of ²⁶Al in the sediment, the exact age of burial cannot be calculated. However, it is possible to estimate a minimum age on the basis of the expected residence time at the surface and the cosmogenic production rate, which depends on the original altitude of the catchment area. The longer the sediment is at or near the surface (i.e., the smaller the erosion rate is), the more cosmogenic isotopes are produced. Once washed underground, these isotopes decay. If the sediment remained at the surface for a very short time, a little amount of isotopes is produced; it follows that after a comparable short burial time, the Al content would be no more measurable. The longer the sediment stayed at the surface, the more burial time is needed in order to completely deplete ²⁶Al. Therefore, in the case of the Raponzolo sediment, the main question is what a meaningful residence time at the surface could be. In order to provide a reasonable hypothesis on the residence time, we can consider the largest dataset available in the Alps: the data from Siebenhengste (Häuselmann et al., 2007). This dataset can be used as a reference for Raponzolo because of the similar settings, being Siebenhengste a karst system located within the higher ranges of the Alps (around 2000 m a.s.l.) in an area which experienced glaciations, as is the case of the Brenta Dolomites. In Siebenhengste cosmogenic dating provided erosion rates ranging from 23 to 470 m/Ma, while all but two have rates <150 m/Ma, indicating slower (pre- or interglacial) erosion. An averaged value yields 67 m/Ma, which translates into an inherited ¹⁰Be amount prior to burial of 169,000 at/g. Divided by the estimated production rate in that area of 18.09 at/g/a, this gives 9,300 years residence time at the surface. The fastest, probably glacial, erosion rate gives a residence time of 1,300 years.

Since production rate is dependent on altitude, the model should also consider the approximate height of the original catchment area of the Raponzolo sediment. In order to model altitudes, production rates and erosion rates, we can use as prerequisites the available data: 1) the amount of ¹⁰Be remaining in the sample measured to be 8,800 at/g; 2) no measurable ²⁶Al is present due to its complete decay. The lack of ²⁶Al can be fixed to be less than 5,000 at/g, twice the value of the blank. Considering these values, it is possible to create a model and back-calculate catchment altitudes and ages (Supplementary Table S4). This model shows that the fast erosion rate (surface residence time of 1,300 years) can be excluded (red ages in Supplementary Table S4) since it would give consistently measurable amounts of ²⁶Al (>10,000 at/g) in the sample. Therefore, we hitherto used the mean erosion rate of 67 m/Ma in the model (Figure 10). With this erosion rate, the model provides the minimum elevation of the catchment area (which is 1,200 m a.s.l.) and the minimum age that fulfills all prerequisites (around 5.25 Ma) (Figure 10). However, it is important to consider that this model output is based on the assumption that in Adamello and Brenta erosion and uplift were constant in time and space at the million-year timescale neglecting the effect of local differences as for instance fault displacement and differences in rock erodibility. This assumption is supported by thermochronologic data that in Adamello and Brenta do not resolve changes in the rate of exhumation after 4 Ma (Revermann et al., 2012) and that indicate possibly only little differential exhumation between the two massifs since 10 Ma (Heberer et al., 2017). Thus, our model points to the hypothesis that burial in the cave happened before 5.25 Ma.

The Raponzolo Cave presents morphologies consistent with a phreatic and/or epi-phreatic origin (Figure 3B). The cave is probably only a fragment of an ancient karst system that has been eroded and uplifted to its present altitude (2,560 m a.s.l.). The conduits originally formed close to the water table level, which could have been situated at the level of the late Miocene valley bottom. The catchment area was situated in the northern part of the Adamello batholith up to the Tonale Unit to the north of the Periadriatic line. At present, these areas are separated from the Tovel Valley by the Rendena and Meledrio Valleys developed along the South Giudicarie Line and culminating in the Campo Carlo Magno pass at 1,682 m (Figure 11). Unfortunately, the irregular layering of the granitic sediments in the cave is not diagnostic of the direction of water flow during the sediment deposition, so we cannot discern if the sediment was flushed within the karst system from the Tovel valley or from the Rendena valley. These two possibilities are represented in Figures 11, 12. In the profile of Figure 12, the present topography is projected at theoretical altitudes during the late Miocene considering, for simplicity, a constant and uniform erosion rate of 0.25 km/Ma and rock uplift rate of 0.35 km/Ma in agreement with several studies on the evolution of this alpine region (Revermann et al., 2012; Heberer et al., 2017 and references therein). This simplified assumption does not take into account differential erosion and uplift depending on lithologies and tectonic subdomains, but allows providing a general idea of the potential paleolandscape. Indeed, the Mediterranean salinity crisis and the base level dropdown during these times should have been the footprint of the present time hydrographic network in the Adamello-Brenta region, similar to what occurred in the Lepontine dome (Garzanti and Malusà, 2008). If the sediment filled the karst system entering from the Rendena Valley, the clasts of the Tonale Unit had to be transported from the Sole Valley (766 m at present-day Dimaro) uphill along the Meledrio Valley, and across Campo Carlo Magno Pass (1,682 m at present day). If the sediments had to be transported inside the Tovel valley, they would have overcome also the Grosté Pass (2,442 m at present day, Figure 11). From the data available and literature it is not possible to assess the hypothesis that the Meledrio or Tovel valleys were inverted at that time, allowing an efficient fluvial sediment transport from Tonale to Brenta. However, if the present topography should generally mirror the Miocene landscape, a relief inversion of these incisions after the Messinian sea level dropdown is unlikely suggesting that an uphill sediment transport from Tonale to Brenta would have been possible only by means of glaciers. The Adamello and Brenta massifs have been strongly affected by Quaternary glaciations, and during the Last Glacial Maximum, a glacial tongue from the Sole Valley filled the Meledrio Valley and surpassed the Campo Carlo Magno Pass where the reconstructed elevation of the glacier was around 2,100 m (Trevisan, 1939; Carton and Baroni, 2017). Glaciers could have used the same transport route also during more ancient glaciations and remains the best candidates for the transport of sediments of the Tonale Unit from the Sole Valley up to the Raponzolo cave entrance. This hypothesis poses an interesting dilemma because Miocene glaciations in the Alps have never been documented. Instead, sedimentary evidence of localized latest Miocene–Early Pliocene glaciations are known from Greenland (Larsen et al., 1994) to South America (Mercer and Sutter, 1982). The North Atlantic records a major cooling episode and increase in global ice volume in the period from 6.26 to 5.5 Ma that was marked by 18 glacial-to-interglacial oscillations, with the most prominent glacial phases at 5.75 and 5.51 Ma (stages TG20 and TG12; Hodell et al., 2001). These ages are within the possible range of the sediment infilling of Raponzolo being older than the minimum cosmogenic burial ages of the sediments calculated in the cosmogenic production model presented in chapter 4.2 (Supplementary Table S4). Also, the expected altitude of the source between 1,200 m (Rendena Valley sink, Figure 12) and 1700 m (Tovel Valley sink, Figure 12) is in agreement with the minimum altitude catchment calculated by the model.

The modest increases in global ice volume inferred from the benthic δ¹⁸O signal (Hodell et al., 2001) suggest that Late Miocene glaciations were not as widespread as the Quaternary ones. In this scenario, local Alpine glaciers were probably not able to reach the Po plain and, therefore, no glacial sediments have been preserved, aside of potential local traps like caves.

A problem for this interpretation remains the roundness and well sorting of the Raponzolo sediment, which is in contrast with a glacial origin, pointing to a fluvial or aeolian transport instead. However, the first action of glacier flows is bulldozering the sediments already present at the valley bottoms (Rossato et al., 2018), which are usually rich in fluvial components. Therefore, a recycling of fluvial sediment by glacier tongues is consistent with the grain size distribution and shape, as well as with the presence of well-preserved biotite, which has not been weathered after burial (Petersen and Rasmussen, 1980; Föllmi et al., 2009). However, we cannot exclude that the most rounded quartz grains could be related to recycling of aeolian sediments, which is also consistent with an arid-cold glacial environment and with the presence of silt sized grains in the Raponzolo cave sediments (Wright, 2001).

Cosmogenic data do not constrain a definitive age of the sediment burial, but point to a minimum age of 5.25 Ma. However, it is possible to advance additional hypotheses on the paleo-landscape during cave formation and subsequent infilling. Indeed, thermochronologic data indicate that during the late Miocene, from about 8 Ma, the Adamello batholith was exhuming rapidly to near-surface depths at about 0.65 km/Ma in response to uplift induced by tectonic activity, whereas during the Plio-Pleistocene exhumation proceeded on average at a lower rate of about 0.35 km/Ma (Reverman et al., 2012). In Brenta, on the other side of the Giudicarie line, thermochronologic data from flysch sediments on the eastern foot of the massif (Ponte Pià Formation, AFT = 9–10 Ma) indicate 3 to 2 km of rock removal since 10 Ma, which corresponds to an average exhumation rate similar in range but possibly slightly lower than the one estimated for the Adamello massif during the late Miocene (Heberer et al., 2017). Altogether, the thermochronologic data from Adamello and Brenta, and the new data gathered from Raponzolo Cave, indicate that during the late Miocene the exhumation of the two massifs was synchronous, but the pace was possibly slightly different. This means that Adamello was possibly exhuming faster than Brenta and that this evolution may have favored a potential transfer of sediments (fluvial or glacial) from Adamello-Presanella toward Brenta. A phase of uplift and exhumation might also have favored, at the same time or shortly later, a local base-level fall; accordingly, this would be a suitable scenario for the formation of an epiphreatic cave system and its infilling. Finally, the present-day elevation of Raponzolo Cave roughly corresponds to the lower limit of its sediment source in both Adamello and Tonale as indicated by the AFT ages. This suggests that the Raponzolo sediments represent a remnant uplifted late Miocene landscape including the high elevation reaches of Tonale and Adamello, and Brenta, which was probably slightly lower in elevation as it is still today as suggested by the Ponte Pia Formation AFT ages. In this paleo-landscape, the valleys separating different geological domains (Adamello, Tonale, Brenta) were likely not as deeply entrenched as today, allowing an efficient transfer of sediment from the north-west to south-east across major tectonic lineaments, partially by fluvial systems and occasionally by glaciation events. This observation is consistent with recent studies (Winterberg et al., 2020) showing that major river valleys in inner parts of the Southern Alps (i.e., Adige Valley) were not all yet deeply carved during the Messinian sea-level drawdown.