Tectonic control on karst processes in Pasvalys Area, North Lithuania

Abstract

Karst processes are active in the northern part of Lithuania and cause different problems for the local community. The activity is related to sub-cropping of the Upper Devonian (Tatula Formation) gypsum-carbonaceous succession under a thin (<25 m) Quaternary cover. The Pasvalys cluster of karst sinkholes is distinct by anomalous density of karst features. The structural conditions and lithological variations were studied in relation to karst processes in Pasvalys Town and vicinities. A close correlation of those processes with tectonic structures was recognised. Pasvalys Town is situated within the Pasvalys uplift that is characterised by intense dissolution of the upper part of the evaporitic-carbonaceous Tatula Formation suggesting intense ground water infiltration within the uplift. Therefore the potential of karst activity is rather exhausted here. By contrast, the adjacent Lėvuo-Mūša depression, located west of the town, shows intense pervasive gypsum dissolution of the lower part of the Tatula Formation that resulted in preservation of the upper (Nemunėlis) gypsum layers from erosion processes. It is associated with the high potential of recent dissolution processes and formation of karst features. A similar scenario is identified north of Pasvalys Town in the Maskoliškės depression. The most intense karst processes occur along the high-gradient boundaries of the aforementioned structures. The Pagojis depression, defined in the south, comprises only little affected by pervasive dissolution Tatula succession that also has the high potential for development of karst features. The regular pattern of some sinkholes along lineaments suggests that the fracture system dissecting Devonian sediments also contributed to the uneven distribution of dissolution processes.