Analyses of gas chromatography/mass spectrometry show that β-carotane and its homologues are quite rich and ubiquitous in Karamay crude oil

with β-carotane contained in a few samples more than 30%. Such bio-mark compounds which have important significance in geology

may result from algae rich in carotenes.Since almost all β-carotane can be transformed through thermodegradation into homologues with low molecular weight at a greater extent

as compared with the transformation of stereoisomers of steroids and terpenoids

its relative abundance thus can be considered as a more effective index for thermal evolution.The ratio of γ-carotane to β-carotane may also be an important index. The γ/β ratio increases with thermal evolution and decreases with biodegradation.