ABSTRACT
Sediments form a relatively thin surface layer of the Earth’s crust, covering the igneous or metamorphic rocks that underlie them. The raw materials from which the sedimentary rocks have been formed include accumulations of loose sand and muddy detritus, derived from the breakdown of older rocks and brought together and sorted by water or wind. The components of sediments become hardened into sedimentary rocks such as sandstone, quartzite, limestone and shale by changes which commence soon after the sediment has accumulated. The texture of a sedimentary rock reflects the mode of sediment deposition, diagenesis during burial and subsequent weathering when uplifted and exposed at the surface of the Earth. The compositions and textures of sedimentary rocks are controlled by the processes that operated during their formation; and these processes are in turn governed by the environment in which sedimentation takes place.
