Karst systems analyzed using borehole logs — Devonian carbonates of the Świętokrzyskie (Holy Cross) Mountains, central Poland

The methodological assessment of the quality and the usefulness of borehole logs for karst analysis versus the use of data obtained via direct observation is the first objective of this paper. The second objective of the paper is to present — in the form of a case study — regional analysis of karst in Devonian carbonates of the Świętokrzyskie (Holy Cross) Mountains, south-central Poland. The subjects of the discussion are karst evolution stages, karst horizons, and their relationship to relief development. The analyzed examples (sites) presented herein, where the reliability of borehole data has often been verified by field observations, prove that descriptions of borehole logs can be used for karst analysis. However, borehole log data analysis is subject to many limitations and requires extensive validation. The basic condition that has to be met is the explicitness of the descriptions of karst forms in borehole logs. The number and the length of logs (“macro-records”) as well as the number and the size of karst forms (“micro-records”) are other important factors that affect log interpretation quality. Nevertheless, the principal general advantage of borehole log analysis is the representative nature of the obtained information. The formation of karst horizons independent of the lithology and the stratigraphy of the Kowala Fm in the Świętokrzyskie Mountains but controlled by external morphological factors suggests an isotropic character of this formation. Two general vertical types of karst systems are distinguished in this formation: (1) karst horizons, and (2) extensive karst development without distinct differentiation. The former could have been connected with fluvial base levels whereas the latter represents systems formed within the vadose zone.