Krzysztof Gaidzik

The Mravljetovo brezno v Gošarjevih rupah (MBGR) cave system in central Slovenia provides key insights into the role of dedolomitization in speleogenesis within mixed carbonate successions. Detailed geomorphological mapping, structural analysis, LiDAR-based morphometry, sedimentology, and U–Th and OSL geochronology were integrated to reconstruct cave and landscape evolution. Dedolomitization acted as an early-stage preconditioning process, enhancing porosity, permeability, and mechanical weakness along bedding planes and fractures, thereby guiding initial conduit development. Cave passages are strongly aligned with Dinaric-oriented fault systems, indicating structural control predating Miocene tectonic reactivation. Morphological features such as ceiling channels, cupolas, feeders, and pendants reflect a complex interplay between structurally guided phreatic inception and later epiphreatic to vadose modification. U–Th ages up to ~380 ka and OSL-dated sediments at ~87 ka constrain major phases of vadose evolution to at least the Middle Pleistocene, while Holocene speleothems record renewed calcite deposition under stabilized conditions. Progressive uplift and valley incision drove long-term groundwater-level lowering, transitioning the system from phreatic to dominantly vadose conditions. Present morphology is further modified by condensation corrosion linked to active cave ventilation. The MBGR cave demonstrates how dedolomitization can fundamentally influence speleogenetic pathways and highlights caves as valuable archives of tectonic, climatic, and geomorphic evolution in prealpine karst settings.

The Coulomb stress transfer analysis is based on the hypothesis that failure on a fault plane occurs when the Coulomb stress exceeds a certain threshold. Positive Coulomb stress changes are thought to bring faults closer to failure, whereas negative ones inhibit failure. The Colca Region in Central Andes, southern Peru, is prone to small- to moderate-sized (Mw ≤ 6.0) shallow (< 20 km) earthquakes associated with normal and strike-slip crustal faults within the overriding plate in the Nazca-South American subduction zone. Along with the activity of the Sabancaya volcano, which in recent years comprised mainly of ash and fumarole emissions, this region offers an opportunity to investigate the complex relationship between seismic and volcanic activity, their potential interplay, and triggering factors.To explore these dynamics, we carried out a Coulomb stress transfer analysis examining the interactions between source faults of 28 significant recent earthquakes (1991-2022), as well as the impact of magmatic inflation (2013-2022) on seismic events. The results confirm a tectonic origin for most earthquakes, while the magmatic source appears to play a secondary role, primarily amplifying the effects of prior seismic activity. However, the Coulomb stress transfer does not seem to be the main factor impacting the seismicity of the Colca Region, as most of the analyzed source faults were not brought closer to failure due to a positive stress change. Preceding seismic activity induced positive Coulomb stress changes on source faults in 43% of the events, while negative stress changes potentially inhibited 25%. Magmatic inflation contributed to positive stress changes in 22% of cases but also induced negative changes in a similar proportion. Notably, no direct connection was identified regarding the significant increase in seismic activity in 2013, which appeared to be potentially correlated with the start of the fumarolic emissions (late 2012) by the Sabancaya volcano.While the coseismic static Coulomb stress change does not fully account for the complexity of seismic and volcanic activity and their interplay in the Colca Region, it provides valuable insights into active geological processes and highlights open questions warranting further investigation.This research was funded by the National Science Centre (Poland), Grant Number 2020/39/B/ST10/00042.

Dedolomitization is a geological process where dolomite undergoes transformation into calcite via the influx of aggressive Ca-rich solutions derived from various sources (e.g., evaporite dissolution). This conversion can take place in diverse environments. Our study focuses on a unique occurrence of dedolomite within a cave environment in the Mravljetovo brezno v Gošarjevih rupah cave located in central Slovenia. The cave walls exhibit distinctive yellowish and reddish crusts and covers that originated from dedolomitization process developed within this cave system.Macro- and microscopic observations reveal that yellowish lithologies are of sedimentary origin, where dominating dedolomite (i.e., replacive calcite) is associated by mainly detrital particles with a high content of quartz, muscovite, clay minerals, and lithoclasts. In contrast, red lithologies are associated with the transitional zone between sedimentary layers and the host rock dolomite, featuring peculiar calcite crystals with abundant pore space and intercrystalline iron oxides and clay. The transitional zone itself consists of a calcite mosaic with smaller dolomite remnant embedded within the calcite structure.The primary objective of this study is to conduct a comprehensive mineralogical analysis (XRD, SEM-EDS, EMPA, μXRF, CL, and Raman spectroscopy), aiming to recognize their interrelationships and utilize them as proxies for understanding the processes leading to dedolomitization.Dedolomitization is evidenced by the abundance of corroded dolomite rhombs infilled with calcite, coupled with the development of moldic (dissolution-related) porosity, and subsequent crystallization of vein calcite. Detrital quartz reveals embayed crystal boundaries, as well as rounded lithoclasts enriched in clay-group species (e.g., illite). Subordinate detrital apatite, rutile, and zircon were also recognized. Besides, some mineral phases of authigenic origin were detected based on their habits and textural relationships. These include clay-group species (i.e., kaolinite, illite, and/or possible mixed-layer clays), as well as S- and Na-rich apatite, and fluorite. The formation of dedolomite was followed by the decrease of Mg and increase of Fe as evidenced by elemental mapping. These changes can reflect oxidizing conditions and subsequent precipitation of Fe3+ in hematite or goethite/lepidocrocite mineral phases that stained dedolomitized regions red to yellow.Furthermore, we seek to investigate the potential influence of these mineralogical dynamics on cave formation and speleogenesis. All these findings can contribute to a better understanding of geological and geochemical mechanisms governing dedolomitization processes within cave environments.This work is funded by the Slovenian and Polish research agencies (ARRS and NCN) through the bilateral Polish-Slovenian research project CEUS (project code in Slovenia: N1-0226; project code in Poland: 2020/39/I/ST10/02357).