Carotenoids are a major group of pigments widely distributed in nature and are commonly preserved as derivatives in sedimentary records after diagenesis and catagenesis. Among them, the aromatic compounds are mostly associated with photosynthetic sulfur bacteria and have been used in paleoenvironment reconstruction. For example, the detection of aromatic carotenoids in sedimentary rocks has been interpreted as photic zone euxinia (PZE) during deposition, and further inferences can be drawn regarding paleowater depth, microbial communities, nutrient availability, etc. Aromatic carotenoidbased PZE have been widely used in oilsource rock correlation, exploring life evolution, understanding drivers of mass extinctions and as triggers of oceanic anoxic events. In this study, we assess the pattern of carotenoids in the Oligocene Anjihaihe Formation of the southern Junggar Basin to provide paleoenvironmental and paleoecological interpretations. Our results show predominance of chlorobactene and isorenieratane from green sulfur bacteria indicative of PZE during deposition. The dominance of green sulfur bacteria over purple sulfur bacteria in carotenoid input suggests a deep and large paleolake during deposition, in which the occurrence of PZE was likely related to the evaporative water conditions during the paleoclimatic shift from wet to dry conditions during late Oligocene. Additionally, we report a new diaromatic carotenoid with 38 carbon atoms that was potentially synthesized by cyanobacteria. Consistent with tectonic viewpoints, the postOligocene uplift of the north Tian Shan suggests a possibly larger paleolake during the Oligocene deposition than the current range of Anjihaihe Formation in the south of Junggar Basin.