ABSTRACT
This chapter discusses detrital sediments and their grain-size variations, the great diversity of biogenic sediments, and evaporite deposits formed by salt precipitation from seawater. It explores the creation and composition of sediments and the nature of sedimentary structures. It describes how a layer of loose sand, such as present-day beach sand, turns into rock. Diagenesis is a physical process that leads to increased density and mechanical strength of the geological material. Diagenesis also acts on other loose materials that are not listed in the common classification of sediments, such as pyroclastic deposits and fault-filling materials. Diagenesis includes complex physicochemical processes that cause solid sediment material and pore water to interact. Spheroidal grains are not very deformable in themselves and sediments composed primarily of these grains generally do not compact to a significant degree. In saturated sediments where the pore size is larger than a few tenths of a millimeter, water is able to circulate.
