| Mixed clastic and carbonate deposits developed extensively in L levels of Zhujiang Formation in the southern Huizhou Depression, Zhujiangkou Basin. Based on seismic sections, drilling data, and core data, the lithological character, spacial distribution and depositional model are studied. The mixed deposits can be subdivided into two types, namely facies mixing and in-situ mixing. The facies mixing deposits the fine grain mixing of layers of siliciclastic shale and micritic carbonates in the overlapping boundary area between shallow marine delta and carbonate platform in a low-energy environment. The in-situ mixing deposits the sand-size particle mixing of siliciclastic sand and bioclastic limestone in a unique layer of delta front in a high-energy environment. The carbonate layers deposited by in-situ mixing play a complex role in the storage capacity and flow performance of reservoirs in L levels. The facies sequence of shale-carbonate-sand-carbonate-shale is identified in in-situ mixing. The factors such as input of terrigenous clastic deposits, paleo-topography, sea-level fluctuation and delta migration influenced the euphotic zone, and controlled the origin and distribution of clastic-carbonate mixing. |
