Paleoclimate reconstructions in source area by using mud rocks geochemical composition: modern approach, possibilities and constrains

Research subject. Paleoclimate reconstructions in source area. Aim. To identify the possibilities and constrains of using a number of geochemical characteristics of mud rocks (CIA, RW index, modules and modular diagrams, etc.) when reconstructing data on the near-surface humidity and mean annual temperatures (MAT) for catchment areas of the geological past. Key points. The types of climate and paleoclimate classifications, features of paleoclimate reconstruction with a special emphasis on the geochemical composition of fine-grained rocks are considered. N.M. Chumakov's paleoclimate classification is put forward as the most objective. Geochemical criteria are given, according to which it’s possible to reconstruct individual parameters necessary for its application. Thus, it is possible to classify various strata as weathering products of source rocks in a humid, arid/semiarid climate not only using the modular diagrams of Ya.E. Yudovich and M.P. Ketris, but also when studying the titanium geochemistry. In addition, the equation recently proposed by K. Deng et al. allows one to reconstruct the MAT in the area of source rock erosion using the CIA values in a shallow marine and deltaic sediments. However, calculating the CIA index in rocks has a number of constrains, many of which can be overcome. The discussion is supported by several examples of the rational application of the integrated geochemical approach to reconstructing the climate characteristics for Upper Riphean and Upper Vendian strata that bearing red beds, Lower Vendian strata recording glacial and interglacial events, and Upper Devonian formation with a heterogeneous complex of source rock and facies. Conclusions . It is possible to reconstruct various climate characteristics in paleocatchment area for certain strata using the geochemical characteristics of mud rocks only if they have been comprehensively studied and the researcher takes into account the multifactorial nature of the processes determining their composition.