THE ROLE OF FAULTS IN THE FORMATION OF THE OKHOTNICHYA CAVE (BAIKAL REGION)

Abstract

The paper presents the results of an analysis of faults of different ranks near the Okhotnichya Cave in Pribaikalye, aimed at identifying their role in the formation and evolution of the cave and its adjacent areas. This was done using rank-wise structural-paragenetic analysis of faults, which forms the basis of a specialized mapping tool for fault zones. Factual evidence was obtained through several methods. The speleoinitiating fracture network was studied based on the results of the cave digital topographic survey performed using Leica DistoX 310 laser rangefinder. The therewith-generated 3D-model of the cave allowed making up a detailed plan of the passages for linking to the local geological-structural observations with mass fracture measurements and studying dip directions and strike orientations of the cave fractures. The results stated that the passages in the cave network correspond to the paragenesis of the right-lateral NNE trending strike-slip fault. Local analysis of rock fracturing within the cave made it possible to determine the type of kinematics of speleoinitiating fractures and to verify the reconstruction of the fault zone of the supra-local level. It has been stated that narrow tunnels follow the local NNE- and WNW-oriented strike-slip faults, and large chambers and grottoes follow the extension structures - ENE- and NE-striking normal faults. The lineament analysis of the cave-adjacent area revealed that the strike-slip fault network of the cave is an element of paragenesis of the regional normal fault, typical of the late-orogenic Baikal rift system. Thus, the conducted research showed that the genesis of the Okhotnichya Cave has a mixed character and provided the possibility of analyzing the karst caves' spatial patterns to reconstruct kinematic types of faults at different hierarchic levels - local, supra-local, and regional.