Oil-Source Correlation in the Ordovician and Carboniferous Strata from the Southwestern Ordos Basin (China): Implications for a Multivariate Statistical Approach

kerogen deposited in a paralic facies, whereas the Wulalike Formation exhibits lower TOC values (average 0.31%) and represents highly mature Type I marine source rocks. Multivariate statistical analysis shows that the biomarker characteristics of the Yanghugou oil sands are intermediate between those of the two source rock systems. The MI-OMOI diagram further demonstrates that the Yanghugou oil sands have a mixed origin, with contributions from both the Yanghugou and Wulalike Formations, while the Wulalike oils are predominantly self-sourced and self-reservoired. Overall, the composite indices method established in this study effectively improves oil-source identification accuracy under conditions of strong maturity contrast and provides new insights for hydrocarbon exploration in structurally complex areas.