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中国早古生代烃源岩由于缺乏镜质组，加之成熟度较高，常现成熟度指标较难应用，长期以来，对这套烃源岩成熟度评价一直存在问题。塔里木盆地是中国最大的以早古生代地层为主的含油气盆地，在寒武系和奥陶系生油岩中发育有海相镜质体。应用有机岩石学方法主要对塔里木盆地四口深井岩芯样品进行了研究，发现海相镜质体反射率与孔深呈正相关，且其相关性优于沥青反射率，人工热模拟实验结果进一步表明，海相镜质体成熟作用轨迹不同于镜质组。在R＜1．5％时，其反射率比镜质组低；在R＞1．5％时，其反射率比镜质组高。结合天然剖面与热模拟系列样品研究成果，发现R与Ro的相关性可划分为三个阶段，可分别近似用三个直线方程表示：根据海相镜质体反射率实测结果，应用这些方程计算出等价Ro，可较客观地评价早古生代烃源岩成熟度。
Due to the lack of vitrinite and the high maturity, the paleozoic source rocks in China are often difficult to be applied due to their maturity. For a long time, the evaluation of maturity of this source rock has always been problematic. The Tarim Basin is the largest petroliferous basin dominated by the Paleozoic strata in China. There are marine vitrinites in the Cambrian and Ordovician source rocks. The application of organic petrology mainly studies four deep core samples in Tarim Basin. It is found that the vitrinite reflectance has a positive correlation with the pore depth, and its correlation is better than that of bitumen. The artificial thermal simulation results further show The path of maturation of marine vitrinite is different from vitrinite. At R <1.5%, the reflectivity is lower than that of the vitrinite; at R> 1.5%, the reflectivity is higher than that of the vitrinite. Combined with the results of the natural section and the thermal simulation series of samples, we find that the correlation between R and Ro can be divided into three stages, which can be approximated by three straight line equations respectively: Based on the measured results of the vitrinite reflectance, the equations Equivalent Ro, can more objectively evaluate the maturity of the Early Paleozoic source rocks.