The discovery and significance of the estuarine facies in the Upper Triassic Adula-Duogaila Formation, Chaya region, Qamdo area, Xizang
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摘要:
通过对昌都市察雅县岗卡村阿堵拉组—夺盖拉组剖面沉积构造、岩性组合、沉积序列等进行综合研究，结果表明：（1） 阿堵拉组—夺盖拉组沉积期为河口湾相沉积，进一步可划分河流亚相及潮坪亚相，河口湾相的识别与前人提出的三角洲相、滨岸相有较大差异。（2） 河流亚相可进一步识别出河床次相、河漫滩次相。河床次相以沉积厚层块状砾岩、长石岩屑砂岩为特征，发育板状、槽状交错层理、平行层理等沉积构造；河漫滩次相沉积粉砂岩、泥岩组合，见碳化植物碎片，发育沙纹层理。（3）潮坪亚相可进一步识别出潮下带、潮间带及潮上带次相，潮下带次相沉积泥质粉砂岩、岩屑砂岩等组合，发育沙纹层理；潮间带次相沉积粉砂岩、泥岩组合，发育干涉波痕、波状层理、透镜状层理等沉积构造；潮上带次相沉积泥岩、含碳质泥岩组合，岩层夹有粉砂岩透镜体，发育水平层理、雨痕等沉积构造。
Abstract:The study of sedimentary structures, lithological combinations, and sedimentary sequences of the Adula-Duogaila Formation in Gangka Village, Chaya County, Qamdo City, shows the presence of estuarine facies during the sedimentary period of the Adula-Duogaila Formation. Further analysis subdivides the estuarine facies into fluvial subfacies and tidal flat subfacies. The fluvial subfacies can be further subdivided into riverbed suborder facies and floodplain suborder facies. The riverbed suborder facies is characterized by thick-bedded conglomerate and feldspathic litharenite, while the floodplain suborder facies is distinguished by deposits of siltstone, mudstone, and carbonized plant fragments. Sedimentary structures such as cross-bedding, trough cross-stratification, and parallel bedding can be observed in the fluvial subfacies. The tidal flat subfacies can be further distinguished into subtidal, intertidal, and supratidal suborder facies. The subtidal suborder facies is characterized by mudstone and lithic sandstone, with the development of ripple bedding. The intertidal suborder facies is characterized by deposition of siltstone and mudstone, with interference ripple marks, lenticular bedding, and wave-like bedding as prominent sedimentary structures. The supratidal suborder facies is characterized by mudstone and carbonaceous mudstone, with interbedded lenses of siltstone, and sedimentary structures such as horizontal bedding and rain prints.
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Key words:
- Qamdo area /
- Upper Triassic /
- estuarine facies /
- sedimentary suborder facies
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