Analogues of Flint Clays in Soviet Literature

Abstract-The term "flint clay " used in USA and several other countries, corresponds very closely to the term "toasted bread (sukhar) clay". In both USA and U.S.S.R., the typical occurences of"toasted clays " are confined to deposits of the lower Carboniferous. In their properties and occurrence the well-studied toasted clays of the Borovichy deposit (Novgorod province) are highly similar to the flint clays of Missouri, differing significantly only in having lower bulk specific gravity and higher porosity than do Missouri flint clays. Varieties with excess free alumina (diaspore, boehmite) are observed both among "toasted " and flint clays. The author suggests he term "toasted complex " (sukharnii kompleks) which corresponds toW. D. Keller's term "flint clay facies". The clays of the "toasted complex " are sediments of ancient swamps and lakes which contained rich vegetation. Their source material was finaly dispersed silicate particles transported from dry land. The structure and properties of toasted clays are explained by the precipitation fkaolinite as colloidal clumps in which crystallization ccur-red with formation of intimate intergrowths and variously oriented segregations. THANKS to the kindness of Professor W. D. Keller, the author had the opportunity to familiarize him-self with the peculiarities and occurrence of clay

Annotated record of the detailed examination of Mn deposits retrieved from lakes Krasnoye (Punnusjarvi) and and Borisovskoye (Borisov), Russia

The study of lake deposits containing iron-manganese nodules is of significant interest for the understanding of one of the continental manganese and iron concentration processes. In the USSR, much attention has been given to the formation conditions of ore accumulations in the Leningrad region and Karelia. Semenovich came to the conclusion that Fe super(+3) and Mn super(+4) entered the lake during a long period of drought and were buried together with organic matter of plant origin. In the lake muds, manganese and iron are reduced; readily soluble compounds of Fe super(+2) and Mn super(+2) are transported by bottom waters. Oxidation of iron and manganese to Fe super(+3) and Mn super(+4) occurs, precipitating oxides on the bottom that form nodules and incrustations. This scheme of lacustrine ore genesis by the accumulation of manganese and iron is well founded