Sedimentary Environment and Provenance Tracing of Clastic Rocks from the Triassic Yanchang Formation in the Western Margin of the Ordos Basin
[Objective]There are still some disagreement and deficiencies on understanding the sedimentary environ-ment and provenance from the Triassic Yanchang Formation in the middle of the western margin of the Ordos Basin[Methods]Through geochemical methods,sixteen sand and mudstone samples from different sections of the Late Triassic Yanchang Formation were tested and analyzed,and the sedimentary environment,source rock types,and tec-tonic background of the Yanchang Formation clastic rocks were evaluated.[Results]Sandstone types are mainly lithic and feldspathic sandstone,the source areas experienced weak-moderate weathering,and the samples were little affected by the recycling. The source is related to the upper crust material. The Yanchang Formation is in an oxidation-weak reduction freshwater sedimentary environment,with an arid-semi-arid paleoclimate,and the Third member is in a weak oxidation brackish water environment with a warm and humid paleoclimate. The source rocks are primarily felsic,and the provenance of the Third member of the Yanchang Formation is complex,with a little interme-diate rock. The source area of the Yanchang Formation has a tectonic background of an active continental margin,while the tectonic background of the Third member source area is complex and is related to both a continental island arc and an active continental margin.[Conclusions]The provenance and sedimentary environment characteristics traced by elemental geochemistry are in good agreement with the lake basin evolution and regional tectonic environ-ment of the Triassic Yanchang Formation.
万方数据
维普
