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Objective The aim was to update the sedimentary characteristics of the widely distributed Triassic dolomite-evaporite paragenesis system in the Sichuan Basin and clarify its development and distribution patterns and main influences， provide new insights for its study and guide the reconstruction of the regional paleogeography. Methods Drill core and seismic data were used to investigate the sedimentary characteristics in the study area from a number of viewpoints and determine the genetic mechanisms of the different types of symbiotic systems and reveal their spatiotemporal distribution patterns and main controlling factors. Results （1） Overall， four types of symbiotic systems are present in the Leikoupo Formation， northwestern Sichuan Basin： （i） thick layers of dolomite interbedded with thin layers of evaporate； （ii） interbedded dolomite-evaporate； （iii） thick layers of evaporite interbedded with thin layers of dolomite； and （iv） overlapping thick layers of evaporite. Types （i） and （iv） are widely distributed throughout the four sedimentary periods in the Leikoupo region. Stacking of thick evaporite and thick dolomite occurs most frequently in the central part of the Lei-3 and Lei-4 sedimentary periods. （2） The uplift of the Longmen Mountain island chain on the western side caused southeastern compression on the basin， and the Xuefeng Mountain uplift to the east restricted the southward migration of the ancient Luzhou Kaijiang paleo-uplift， and the contemporaneous Qinling Mountains southward subduction has been occurred.formed a structural pattern trending almost northeast–southwest in the Sichuan Basin， which controlled the overall northeast⁃southwest distribution of gypsum rocks and symbiotic systems. （3） The significant extent of the Luzhou Kaijiang paleo-uplift caused subsequent migration of the Leikoupo Formation subsidence center toward the west， and the gypsum sedimentary center and four coexisting systems also migrated westward from their earlier dispersed locations. Conclusions The sedimentary properties and distribution patterns of the symbiotic system resulted in four types of symbiotic system： gypsum-dolomitic lagoons， dolomitic gypsum lagoons， gypsum salt lakes， and gypsum salt basins. The paleogeography of each of the four sedimentary periods of the Leikoupo Formation was reconstructed from the distribution patterns of these types of symbiotic system.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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