Оригинален текст
coals and associated shales are important oil source rocks in cerntain deltaic environments, in which selective processes of degradation or reworking increase the content of hydrogen -rich kerogen. the formation of hydrogen-rich kerogen in a deltaic setting is either by preferential concentration of plant cuticles and spores after reworking of delta top freshwater peats, or,by accumulation of delta margin peats under saline conditions. in each case the source rocks and derived oils may be expected to show distinctive indicators of the depositional environment in the associated alkane content, sulphur content, biomarker and carbon isotope signatures.