Abstract: The Lower Cambrian Yurtus Formation source rocks are regarded as the primary source rocks for marine oil and gas in the Tarim Basin. Current understanding of the Yurtus Formation source rocks mainly relies on analyses of outcrop samples from the basin margins and core samples from uplifted areas, while the characteristics of source rocks in slope and depression regions remain relatively unexplored. Understanding the carbon isotope characteristics of kerogen in the Yurtus Formation source rocks is crucial for elucidating hydrocarbon generation mechanisms and establishing oil-source correlations. This study provides a detailed analysis of the organic geochemistry and carbon isotope geochemistry of Ordovician crude oil and natural gas samples from various fault zones in the Shunbei area. By quantitatively evaluating the impact of thermal maturity on the carbon isotopes of crude oil and natural gas, we reconstruct their original carbon isotope compositions. The kerogen carbon isotope composition in Shunbei area crude oil and natural gas was determined through the fractionation occurring between kerogen and hydrocarbon products during formation. The results indicate that oil-sourced kerogen carbon isotopes predominantly range from -32.3‰ to -28.8‰, while gas-sourced kerogen isotopes range from -33.1‰ to -29.8‰. The crude oil and natural gas are primarily derived from a mixed source of benthic and planktonic algae, with some crude oils in the Shunbei area additionally sourced predominantly from planktonic algae. The light carbon isotope characteristics of kerogen suggest that the hydrocarbons in the Shunbei area largely originate from the Yurtus Formation source rocks. Based on variations in hydrocarbon-producing organism assemblages, Yurtus Formation source rocks are categorized into oil-generating rocks dominated by planktonic algae (δ13C > -30‰), oil-gas generating rocks with mixed benthic and planktonic algae sources (-33.5‰ < δ13C < -30‰), and gas-generating rocks dominated by benthic algae (δ13C < -33.5‰). As the thermal maturity of the source rocks increases, early hydrocarbon generation is primarily from planktonic algae, while later stages contribute more from benthic algae (mainly yielding volatile-condensate oils), resulting in heavier isotopes in early oils and relatively lighter isotopes in later oils. Concurrently, the kerogen content linked to oil generation gradually declines, while the relative content of gas-prone kerogen (from benthic algae) increases, leading to a gradual lightening in the overall carbon isotope signature of the kerogen. Thus, the diverse source rock types and distinct kerogen hydrocarbon generation processes result in complex carbon isotope characteristics in hydrocarbons derived from the Yurtus Formation (e.g., isotopic reversals among crude oil components within reservoirs and between the chloroform extract of source rocks and kerogen). These findings provide new constraints for predicting ultra-deep hydrocarbon phase states in the Tarim Basin.