Kodinka Formation mudstones (mainly silty claystones) in the Middle Urals are the main research subject. They have source rocks from Upper Frasnian accretionary orogen in the East European Platform (EEP) east margin. We studied mineral and chemical (major oxides and some trace elements) composition of the claystones for source rocks and watersheds climate reconstructions. During that we traced back to multiple source shift, which was the key to physical weathering improvement and chemical weathering weaking, which, in turn, facilitated delta progradation to the discharge area, also led to the presence of a more distinct geochemical signal of mafic and ultramafic rocks in the erosion products: an increase in the amount of Ni, Cr, Mg and Na in mud deposits. Most likely, this phenomenon was associated with episodes of tectonic activity (and not, for example, with the mountain glaciers buildup), which “obscured” climatic factors, rather than with something else. In this reason, deltaic and associated deposits were excluded from dataset as unreliable when reconstructing climate using the equation of K. Deng et al. and the chemical index of alteration, as well as the robust weathering index and mafic index of alteration. The near-surface mean annual air temperatures values (about 15–20 ∘C) calculated for samples taken from littoral and sublittoral facies, and the characteristics of titanium accumulation in them allow us to assume the existence of a warm humid low latitude climate for the catchment areas of the Kodinka Formation. Apparently, such a climate on the eastern periphery of the EEP began to exist not from the Tournaisian age, as shown on global paleoclimatic maps, but somewhat earlier.
Mel'nichuk et al. (Mon,) studied this question.