| 引用本文: | 苗如霖,范坤宇,郭佩,李向云,孙金佳杰.2026.库车坳陷古近系盐湖边缘沉积地球化学特征对海平面变化的响应[J].地球环境学报,17(3):739-751 |
| MIAO Rulin,FAN Kunyu,GUO Pei,LI Xiangyun,SUN Jinjiajie.2026.Depositional and geochemical response of the Paleogene salt lake margin in the Kuqa Depression to sea level changes[J].Journal of Earth Environment,17(3):739-751 |
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| 摘要: |
| 古近纪时期, 副特提斯海位于塔里木盆地西南部, 库车坳陷盐湖群的南侧。副特提斯海的多次海平面升降可能为库车坳陷的盐湖沉积提供重要的物质基础, 但其盐湖的成因以及主控因素研究仍存争议。文章通过对库车坳陷东北缘库车河剖面古近系库姆格列木群总厚326.12 m的沉积相演化和石膏沉积进行锶同位素分析, 探讨盐湖沉积对古近纪海平面变化的响应及盐湖成因的主控因素。结果表明, 库车河剖面库姆格列木群整体可划分3个Ⅲ级旋回: 第一个Ⅲ级旋回以下部冲积扇砂砾岩和上部厚层石膏为主, 石膏87Sr/86Sr比值在0.709100—0.709132; 第二个Ⅲ级旋回以下部冲积扇砂砾岩、中部膏盐湖膏质泥岩和上部三角洲砂泥岩为主, 石膏87Sr/86Sr比值在0.709267—0.709410; 第三个Ⅲ级旋回以微咸水浅湖膏质泥岩和砂质泥岩为主, 石膏87Sr/86Sr比值在0.709320—0.709467。库车剖面库姆格列木群沉积相和石膏锶同位素的纵向变化是海侵、构造活动和气候变化的综合控制。第一个Ⅲ级旋回记录了冲积扇陆相沉积向蒸发潟湖的转变, 主要受副特提斯海的海侵影响; 第二个Ⅲ级旋回记录了海侵和陆源供应联合影响下的盐湖沉积, 第三个Ⅲ级旋回记录了干旱气候影响下陆源为主的微咸水浅湖沉积。研究揭示了库车坳陷库姆格列木群早期两个主要成盐阶段均受海侵强烈影响, 晚期陆源供应占主导阶段难以形成厚层膏盐岩沉积。库车坳陷古近纪盐湖沉积响应, 为阐明副特提斯海东端海侵范围和时限、中亚气候演化与区域构造活动提供证据。 |
| 关键词: 副特提斯洋 石膏沉积 锶同位素 库姆格列木群 物质来源 |
| DOI：10.7515/JEE2023232 |
| CSTR：32259.14.JEE2023232 |
| 分类号: |
| 基金项目:国家自然科学基金项目（U19B6003） |
| 英文基金项目: |
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| Depositional and geochemical response of the Paleogene salt lake margin in the Kuqa Depression to sea level changes |
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MIAO Rulin1，FAN Kunyu2，GUO Pei3，LI Xiangyun2，SUN Jinjiajie2
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1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, College of Energy, Chengdu University of Technology, Chengdu 610059 , China ；2. Exploration and Development Research Institute, PetroChina Tarim Oilfield Company, Korla 841000 , China ；3. Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications of Ministry of Natural Resources, Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059 , China
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| Abstract: |
| Background, aim, and scope During the Paleogene period, the Paratethys Sea invaded the southwest part of the Tarim Basin and was located to the south of the salt lakes within the Kuqa Depression in the northeastern part of the basin. Multiple episodes of sea-level changes of the Paratethys Sea had potential providing abundant water and material source for the salt lake deposition of the Kuqa Depression. However, the genesis and main controlling factors of the salt lakes in the Kuqa Depression is still controversial. Against this geological backdrop, this study investigates the Paleogene Kumugeliemu Group outcropping at the Kuqa River section in the northern Kuqa Depression, and elucidates the response of saline lake sedimentation to Paleogene sea-level change as well as the primary controls on saline lake genesis via sedimentary facies analysis. Materials and methods In this study, we selected the Kuqa River section in the northern Kuqa Depression for sedimentary facies analysis, and collected 43 gypsum samples from the Paleogene Kumugeliemu Group, which has a total thickness of 326.12 mm (section coordinates: 42°06′48.16″N, 83°05′11.43″E) for strontium isotope analysis, to elucidate the response of salt lake sedimentation to Paleogene eustatic sea-level changes and the primary controls on salt lake formation. Results The Kumugeliemu Group of the Kuqa River section can be divided into three third-order ( Ⅲ) cycles. The first Ⅲ cycle was dominated by early alluvial-fan conglomerate-sandstone and late evaporite lagoon gypsum deposits and its gypsum was characterized by low 87Sr/86Sr values (0.709100 to 0.709132). The second Ⅲ cycle was represented by deposition of early alluvial fan conglomerate-sandstone, middle salt lake gypsiferous mudstone, and late delta sandstone-mudstone deposits. Its gypsum was characterized by higher 87Sr/86Sr values (0.709267 to 0.709410). The third Ⅲ cycle recorded three small-scale lake transgression and regression and was represented by the deposition of lake playa and mudflat, and high gypsum 87Sr/86Sr values (0.709320 to 0.709467). Discussion The varied gypsum 87Sr/86Sr values and lithological association of the Kumugeliemu Group from the Kuqa River section were a combined response of seawater transgression, tectonic activity and climatic changes. The first Ⅲ cycle was affected by the transgression and regression of the Paratethys Sea in the Tarim Basin and the second Ⅲ cycle was collectively affected by the Tianshan uplift, marine transgression and arid climate. Whereas the third Ⅲ cycle was but mainly affected by arid climate and terrestrial sources, without marine transgression of the Paratethys Sea. Conclusions This study reveals that the early two main salt-forming stages of the Kumugeliemu Group in the Kuqa Depression were strongly influenced by marine incursions while the later stage, dominated by terrestrial source supply, was unable to form thick-bedded gypsum-bearing rock deposits. Recommendations and perspectives The depositional response of the Paleogene saline lakes in the Kuqa Depression provides evidence for the transgression range and timing of the eastern Paratethys Sea, Central Asia paleoclimate, and regional tectonics. |
| Key words: Paratethys Sea gypsum deposit Sr isotope Kumugeliemu Group material source |
