Geochemical characteristics of bitumen from the Cambrian reservoir in the Ordos basin, Northern China: Insights into bitumen classification and origin

•The bitumens from the Cambrian reservoir are genetically classified into three types.•Neural network and cross-plot analyses are useful for determing origin of bitumens.•The Type I and II bitumens are derived from the Lower Cambrian source rocks.•Type III bitumen might originate from Changchengian source rocks.