[Objective]In the Lower Yangtze area,thick Early Paleozoic carbonates are potential reservoirs for oil,gas and geothermal resources.In 2021,well Sure1,drilled by the Geological Survey of Jiangsu province in the Subei Basin,successfully detected high-temperature hot-dry rock geothermal resources in the Early Paleozoic carbonates,bringing the Early Paleozoic carbonate sedimentary microfacies and environmental evolution widespread academic at-tention.[Methods]A detailed microfacies analysis was conducted on well Sure 1 in Subei Basin and three field out-crops in the Ningzhen Mountains to reconstruct the sedimentary environmental evolution of the Early Paleozoic car-bonates in the Lower Yangtze area and provide key basic geological information for the exploration of hot-dry rock geo-thermal resources in the study area.[Results]Thirteen microfacies,corresponding to peritidal and shoal environ-ments in an inner carbonate platform setting with no significant change in paleowater depth,were identified by inte-grating sedimentological and paleontological observations.The Cambrian Mufushan Formation and Guanyintai Forma-tion and Early Ordovician Lunshan Formation are mainly silty dolomites with micrite(MF1),silty dolomite(MF2),laminated silty dolomite(MF3),scarce fenestrae bonded dolomite(MF4),fine crystalline dolomite(MF5),fine crystalline dolomite with micrite(MF7).and breccia dolomite(MF8).These strata lack fossils,but laminations,birdeyes,and fenestral structures indicate upper intertidal to lower supratidal environments.The Early Ordovician Honghuayuan Formation is mainly dolomitized peloidal limestone(MF6),intraclastic dolomite(MF9),dolomitized oolitic limestone(MF10),oolitic dolomite(MF11),intraclastic limestone(MF12),and oolitic limestone with echi-noderm fragments(MF13),indicating a high-energy shoal environment.[Conclusions]The Cambrian Mufushan Formation,Paotaishan Formation,and Guanyintai Formation were dominated by an intertidal environment,while the lower part of the Early Ordovician Lunshan Formation and the Honghuayuan Formation were dominated by a shoal environment,and the ancient water depth was relatively deeper.The Cambrian Guanyintai Formation in the Lower Yangtze area is a favorable target for future exploration of hot and dry rock reservoirs.
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