The Formation Conditions of the Evenki Formation in the Lower Reaches of the Podkamennaya Tunguska River

Abstract

The Evenki Formation of the Siberian Platform is studied on the right bank of the Podkamennaya Tunguska River near the settlement of Sulomay (Evenki municipal district of Krasnoyarsk region). The structures and textures of composing sediments is described. The main petrogenic oxides are identified and the normative mineral composition is calculated following this identification. The increase of terrigenous components in the strata indicates periods of enhanced erosion in the provenance area, which is the Yenisei Ridge. In turn, the increased contribution of feldspars in the middle part of the section shows intensification of physical weathering in arid conditions. The principal hypotheses on the origin of the Evenki Formation as well as of other recent and ancient tidal flat and sabkha facies are outlined. We suggest that the facies of the Evenki Formation under study have been accumulated mostly under intertidal and, possibly in part, under lower supratidal conditions, which alternated depending on eustatic fluctuations in the basin. A conceptual model of the genesis of the Evenki Formation on the Siberian Platform is developed.