Composition and development of some soils on glauconitic Cretaceous (Upper Greensand) rocks in southern England

Abstract

SummaryThree soils developed in glauconitic parent materials and differing in water regime have been examined. Particle size distribution and mineralogical data show them to be free of additions of extraneous material and major lithological discontinuities. The principal soil‐forming processes have been physical disaggregation of glauconite grains, translocation of clay, removal of Fe II from the glauconite structure due to charge imbalance following loss of structural K, and oxidation of this Fe II to form hydrous Fe oxides. A randomly interstratified illit‐mectite has also formed by weathering of the glauconite. The evidence of void argillan formation at considerable depth in the coarser textured soils is difficult to reconcile with conventional ideas regarding the formation of such features. The glauconite in these soil parent materials has an unusually low Fe II content, which confers considerable stability on the glauconite surface. As a consequence, the glauconite in these soils is relatively resistant to weathering.