Similar circumstances result in oil being incorporated into fine sediments and settling in near shore waters. In both situations, anaerobic conditions slow any degradation of the oil. On shingle shorelines, the weathering of the mixture of oil and shingle can result in the formation of an asphalt pavement, which may persist for some time. Oil products that are more dense than seawater, such as very heavy oils or fire residues, fall to the seabed where they can remain undisturbed for indeterminate periods and may result in localized smothering of benthic organisms.