ERSC 2P16 Lecture Notes - Lecture 9: Clay Minerals, Granular Material, Whitemud Formation
2 Aug 2015
School
Department
Course
Professor
Document Summary
In general, the better sorted the sediment the greater the porosity. In well sorted sands fine grains are not available to fill the pore spaces. This figure shows the relationship between sorting and porosity for clay-free sands. Overall porosity decreases with increasing sorting coefficient (poorer sorting). For clay-free sands the reduction in porosity with increasing sorting coefficient is greater for coarse sand than for fine sand. The difference is unlikely if clay was also available to fill the pores. For clay-free sands the silt and fine sand particles are available to fill the pore space between large grains and reduce porosity. Because clay is absent less relatively fine material is not available to fill the pores of fine sand. Therefore the pores of fine sand will be less well-filled (and have porosity higher): post burial changes in porosity. Porosity that develops after deposition is termed secondary porosity. Overall, with increasing burial depth the porosity of sediment decreases.
