The Mallorca coastal caves present large amounts of speleothems that have been studied for decades. However, the sedimentary deposits also present in these cases have not been given the same attention. This work is the first study entirely focused on these deposits, specifically the ones found in the Ases cave. These deposits are formed by clay minerals (illitic phases, kaolinite, smectite, and chlorite), calcite and quartz, and minor proportions of dolomite, albite, orthoclase, hematite, and goethite. The grain size and the electron microscopy studies suggested the presence of different sedimentation processes (bedrock degradation, creep or saltation, and suspension) and different origins (authigenic and detrital origins) for the different sediments. Based on these differences, two types of deposits were characterized: autochthonous and allochthonous deposits. The first ones are located on the floor of chambers and corridors in subaqueous zones, indicating the stability of the mixing zone (and therefore the sea level) over time. The second ones appear filling voids on the walls and the ceiling in the terrestrial zone, evidencing the filling of the cavity in the presence of water (during a wet period). These results are very important to complete the understanding of the caves and their evolution and support the relevance of these materials in paleoenvironmental studies.

Limestone corrosion and coastal karst cave (flank margin cave) enlargement are closely related by the mixing zone between meteoric and seawater, yet quantitative data on corrosion rates in these environments remain scarce. Recent speleodiving exploration in flanking margin caves in Mallorca revealed numerous submerged cavities with different haloclines between 0 and 25 m below m.s.l. To investigate rock-decay mechanisms along these haloclines, exposure trials were conducted in Cova de sa Gleda. Three sets of water-loss rock tablets (WLRT), composed of bioclastic calcarenite limestone and crystalline aragonite (aragonite crystal aggregates), were deployed along a water-column depth profile ranging from 5 to 16 m. After 749 exposure days, tablets were explored by SEM and XRD. Differences in mass show that calcarenite tablets lost an average of 1.89% of their initial mass, while aragonite tablets have lost 8.05%. Corrosion rates varied along haloclines: at 5 m depth (10 to 16 PSU), rates were 3.10% for calcarenites and 11.08% for aragonite; at 10 m (19 to 29 PSU), corrosion increased respectively to 10.8% and 17.93%; at 16 m (>35 PSU, seawater), corrosion decreased to 1.97% and 3.48%, respectively. These haloclines coincide with the height position of notches and other observable corrosion features within the cave. Consequently, these corrosion features present along the cave can be interpreted as proxies of the former position of the groundwater mixing zone.