171 / 2022-02-27 23:17:14

柴达木盆地湖盆迁移与咸化序列发育特征

关键词：青藏高原，柴达木盆地，古环境，湖盆迁移，烃源岩，咸化序列 Keywords: Tibet Plateau, Qaidam Basin, palaeoenviroment, basin migration, source rock, salinization sequence

摘要：柴达木盆地发育于青藏高原北部，受青藏高原隆升影响，湖盆在地质历史时期不断迁移。同时，湖盆沉积经历了多期干旱气候，使得地层在垂向上发育多个咸化序列。通过盆地地层、埋藏史和构造分析，结合地层岩性、盐度和矿化度数据，恢复柴达木盆地新生代以来湖盆迁移过程，以及垂向咸化湖盆发育特点，同时，进一步探讨咸化序列对盆地烃源岩发育的影响。研究结果表明，柴达木盆地湖盆沉积中心古近系路乐河组到下干柴沟组下段沉积时期（E₁₊₂~E₃¹）沉积中心位于靠近阿尔金山前西段和柴西南，下干柴沟组上段至上干柴沟组沉积时期（E₃²~N₁）沉积中心位于英雄岭一带，上干柴沟组沉积时期至上油砂山沉积时期（N₁~N₂²）沉积中心位于柴西北，上油砂山沉积时期至狮子沟组沉积时期（N₂²~N₂³）沉积中心往盆地东部迁移，到第四系沉积时期，沉积中心位域柴达木东部三湖地区。柴西地区在垂向上经历了3个主要咸化序列：第一咸化序列自路乐河组沉积时期至下干柴沟组上段沉积时期，第二咸化序列为上干柴沟组组沉积时期至上油砂山组沉积中期，第三咸化序列为下油砂山组沉积中期至狮子沟组沉积时期。通过古盐度与烃源岩发育的关系证明，微咸水—半咸水阶段有利于优质烃源岩的发育与保存。



Abstract: The Qaidam Basin is located in the northern Tibet Plateau, which continuously migrates resulting from the rise of the Plateau. At the same time, the occurrence of a variety of arid climates leads to several vertical salinization sequences. Here, by combing the analyses of stratigraphy, burial history, structural geology, petrology, salinity and mineralization data, the lake migration and its vertical salinization in the Qaidam Basin since the Cenozoic is unveiled, and the potential of salinization sequences on the development of source rock is further discussed. The results show that the sedimentary center from the Paleogene Lulehe Formation to the lower member of the Lower Ganchaigou Formation (E1+2~E31) is located near the western Aljin Mountain and the southwest of the Qaidam Basin; the sedimentary center from the upper member of the Xiaganchaigou Formation to the Shangganchaigou Formation (E32~N1) is located in Yingxiongling, and the sedimentary center from Shangganchaigou Formation to Shangyoushashan Formation (N1~N22) is located in northwestern Qaidam. From Shangyoushashan Formation to the Shizigou Formation (N22~N23), the sedimentary center migrates eastwards. In the Quaternary, the sedimentary center area is in the Three Lakes area in the east of Qaidam. The western Qaidam mainly exhibited three main salinization sequences: the first is from the Lulehe Formation to the upper member of the Xiaganchaigou Formation, the second is from the Shangganchaigou Formation to the middle of the Shangyoushashan Formation, and the third is from the middle Xiayoushashan Formation to the Shizigou Formation. Through the relationship between paleosalination and the development of source rocks, it is proved that the brackish water is conducive to the development and preservation of premium source rocks.