Unsaturated hydrocarbons (UHCs) of thermocatalytic origin (0.3-1.3 wt %) generated directly from the heteroatomic components of organic matter (OM) of source rock strata were first discovered in Mesozoic-Cenozoic oils. In addition, radiogenic UHCs (similar to 1.5 wt %) were found for the first time among hydrocarbons from bitumens of dispersed OM. It was shown that their presence can be attributed to natural radiation due to radioactive isotopes occurring in the rock. Thus, it was demonstrated that noticeable effects of radiation-induced processes on the composition of rock OM should be taken into account in young (Neogene) deposits as well. Unsaturated hydrocarbons were generated under conditions in which processes involving the carbocationic mechanism did not play a noticeable role. In the samples from Neogene deposits from the southern Anadyr basin, UHCs experienced to a small extent the effect of secondary aging processes, which resulted in reduction in the relative concentration of the least stable components. Dimensionless parameters were proposed such that their numerical values make it possible to differentiate UHCs of different origins and to assess the severity of their aging processes.