THE LATE QUATERNARY "GEYSER VALLEY" IN THE WESTERN FLANK OF THE BAIKAL RIFT (OL'KHON REGION)

Abstract

Geyserites are compact opal-type rocks composed of chalcedony (probably, with opal) with variable tints of brown and less common whitish color. The presence of geyserites unambiguously indicates hydrothermal activity in the Ol'khon region in the Late Pleistocene-Holocene. There are more than ten active springs controlled by inherited NNE-trending faults in the Ol'khon region. All of them contain, however, cold (4-8°C) meteoric water. The Kotel'nikov hydrothermal springs, the only hydrothermal waters on the western coast of Lake Baikal, are located close to its northern edge. Thus, we can state that the hydrogeological regime has evolved from the Late Pleistocene to the recent period. The preceding tectonic processes were characterized by maximal vertical movements during the formation of the Baikal Rift basin. The sharp emergence of the western limb of the Baikal Rift was accompanied by subsidence of the Baikal floor. Active tectogenesis likely stimulated deep progradation of faults within rift walls and surficial discharge of abyssal hydrothermal waters as geyserite accumulations. The spatial juxtaposition of the geyserites and present-day hydrothermal springs implies that the present-day springs inherited the older hydrogeological system.