Unveiling the potential of karst vadose deposits in constraining Quaternary tectonic subsidence

In carbonate coastlines, karst studies have traditionally focused on reconstructing Quaternary coastal uplift and sea level oscillations. However, their potential for investigating coastal subsidence remains unexplored in regions with limited sedimentary records and scientific monitoring. In line with this, our study delved into the utility of karst research for deciphering the Quaternary evolution of the Granada coast in southern Spain—a shoreline marked by a conspicuous scarcity of records and information regarding recent tectonic movements. The current labelling data and the absence of evidence for uplift led to the hypothesis that the Granada coast may be susceptible to subsidence, though this conjecture remained unconfirmed. While submerged marine terraces were clearly identified, they were previously interpreted as consequences of sea-level oscillations. Our multidisciplinary approach integrated karst vadose features, biostratigraphy, and the dating of 22 speleothems to address the potential uplifting or subsiding dynamics of the Granada coast. The findings indicated that the Granada coast experienced emersion between 3.5/2.4 Ma and 650 ka ago. Notably, this uplift predated similar occurrences in neighbouring coastal regions to the W and E, which occurred within the last 200–180 ka. These disparities in timing cannot be solely attributed to sea-level fluctuations, suggesting the involvement of the tectonic activity during the Quaternary. The tectonic likely led to the emergence of the Granada coast and its karstification, followed by subsidence. Furthermore, we identified the extensional faults that caused the coastal subsidence, previously documented in studies conducted in nearby regions. However, until now, their specific impact on the Granada coast had not been comprehensively stated. In summary, our research introduces a novel application of classical karst investigations in the understanding coastal subsidence and the extensional active tectonic. By comparing vadose cave ages with established chronologies in adjacent coastal areas, this approach sheds light on the complex tectonic evolution of coastal regions.