WALL STRUCTURE OF SOME ARENACEOUS FORAMINIFERA FROM THE MAASTRICHTIAN WHITE CHALK (DENMARK)

Abstract

The wall structure of twelve species of arenaceous foraminifera from the Upper Maastrichtian white chalk of Denmark are described. The main part of the agglutinated constituents consists of calcareous particles, i.e. skeletal grains and micrite, but a significant amount of quartz grains also is present. The wall structures are classified into two distinct groups on basis of grain size and texture. The first group includes species with relatively coarse-grained wall texture and quartz grains regularly arranged like a pavement on the test surface. The second group includes species with a fine-grained wall texture and randomly distributed quartz grains. An organic matrix and an organic inner lining are present in all of the species studied. The wall structures and the composition of the agglutinated material show a relation to the composition and diagenesis of the enclosing sediment. The relative abundance of quartz in the chalk and in the arenaceous foraminifera indicates that the agglutination of quartz grains is selective.