Grading of matrix and pebble characteristics in syntectonic pebbly mudstones and associated conglomerates with examples from the carboniferous of Northern Spain

Abstract

Pebbly mudstones are known from many syntectonic sediments. Since particles of clay size can only be deposited in very quiet water, in which pebbles cannot be transported, the occurrence of pebbles and, a clayey matrix proves that such sediments must have been transported by mass movement. If the matrix of the pebble-containing sediment consists of sand grains, the sediment could have been deposited grain after grain. But here too it may have been transported by mass movement, which can sometimes be proved if the matrix grades from sand to silt or even clay size. Three examples from the Upper Carboniferous of the Cantabrian Mountains (N. Spain) are described. Attention has been paid to the characteristics of the pebbles, from which the mechanism of deposition can be reconstructed.