PEDIMENTS IN THE CENTER OF THE EAST-EUROPEAN PLAIN: COMMENTS TO THE PAPER BY V.A. KRIVTSOV AND S.A. PRAVKIN “VALLEY PEDIMENTS IN THE MIDDLE REACHES OF THE OKA RIVER”

Abstract

Publication activity analysis reveals that the term “pediment” has remained popular in geomorphological literature over the past decades. However in the East-European Plain, pediments have still been studied only in its eastern part; for the central part of the Plain this is the first journal publication, that determines its relevance. The mass-wasting pedestals of the Oka river valley slopes, which were described by the authors, are rather elements of local mass-wasting systems – transitional elements of slump slopes, than classical pediments that make a part of landscape planation system. However they do fit the formal definition of a pediment. Data by V.A. Krivtsov and S.A. Pravkin show the close dependence of valley pediment formation in this case on lateral erosion of the river banks: undercutting of a rather long section of the valley side triggers slump activity and subsequent pediment formation. Deciphering the river lateral migrations at a given valley stretch could help to estimate the pediments’ ages. In particular, one of the pediments in the vicinity of the Ryazan’ city is based upon a downstream part of a small Holocene palaeomeander. Small palaeochannels in the river valleys of the region are known to have been formed in the Mid-Holocene. This fact suggests that the palaeochannel was abandoned and the related pediments was formed between 7–8 and 2.5 ka BP. A more accurate estimation of this and other pediment age requires absolute geochronology data from palaeofluvial features in the Oka valley.