References in periodicals archive ?
The dolomite cement in the sandstones of the Burtnieki and Arukula stages has presumably developed from spots connected with fossil fragments, pyrite crystals or other centres, around which the first concretional lumps were formed.
Starting from the lowermost boundary of the Cambrian, the situation changes: marine glauconite, several forms of phosphates, and diagenetic pyrite (also in concretional nodules) appear in rocks.
Accumulations of concretional matter, as well as nodules, and other mineralogical heterogenic phenomena are totally absent.