大巴山地区Marinoan冰川沉积序列及其古气候演化:来自岩石学及地球化学的证据  

Sedimentary sequence and paleoclimate evolution of the Marinoan Glacier in the Daba Mountains:Evidence from petrology and geochemistry

作　　者：彭洲俊 李小刚 熊国庆 谢忠评 冯翔游 陈春竺 彭惠雪 林茂 PENG Zhoujun;LI Xiaogang;XIONG Guoqing;XIE Zhongping;FENG Xiangyou;CHEN Chunzhu;PENG Huixue;LIN Mao(College of Petroleum and Natural Gas Engineering,Chongqing University of Science and Technology,Chongqing 401331,China;Chongqing Key Laboratory of Complex Oil and Gas Exploration and Development,Chongqing University of Science and Technology,Chongqing 401331,China;Chengdu Center,China Geological Survey(Geosciences Innovation Center of Southwest China),Chengdu 610218,China;Chongqing Gas Mine,Southwest Oil&Gas Field Company of PetroChina,Chongqing 400707,China)

机构地区：[1]重庆科技大学石油与天然气工程学院,重庆401331 [2]重庆科技大学复杂油气田勘探开发重庆市重点实验室,重庆401331 [3]中国地质调查局成都地质调查中心(西南地质科技创新中心),四川成都610218 [4]中国石油西南油气田分公司重庆气矿地质技术所,重庆400707

出　　处：《沉积与特提斯地质》2025年第1期69-89,共21页Sedimentary Geology and Tethyan Geology

基　　金：重庆市自然科学基金面上项目(CSTB2024NSCQ-MSX1176);重庆科技大学研究生科技创新训练计划项目(YKJCX2220101);自然资源部沉积盆地与油气资源重点实验室开放基金(cdcgs2022006);国家自然科学基金(U2344209);四川省科技厅中央引导地方发展专项(2023ZYD0153)。

摘　　要：关于新元古代Marinoan冰期,全球处于一个“hard snowball”(硬壳雪球)状态还是“slush snowball”(坍塌雪球)状态,长期存在争议。大巴山地区城口凉桥剖面南沱组冰川沉积物极为发育,出露完整,是研究Marinoan期冰川沉积序列的理想载体,地球化学证据对恢复新元古代末期古气候具有重要意义。南沱组岩石学特征表明,大巴山地区南沱组主要由灰绿色、灰紫色含砾粉砂岩组成。冰碛物沉积地球化学特征揭示,该地区南沱组经历低等化学风化作用,整体处于寒冷干燥的气候环境,化学蚀变指数(CIA)、化学风化指数(CIW)、斜长石蚀变指数(PIA)等古气候指标值均存在明显的旋回变化,即灰紫色含砾质粉砂岩由底部至顶部逐渐从高值减小,灰绿色含砾质粉砂岩则自下而上从低值逐渐增加,表明南沱早期经历过多次冷暖的古气候波动。扬子地区南沱组区域对比及沉积模式表明,南沱冰期可以进一步分为早期渐冻期、中期冰冻期和晚期解冻期,气候冷暖变化主要发生在南沱早期和南沱晚期,浅水沉积区表现尤其明显。因此,大巴山地区南沱组冰川沉积序列及古气候变化证据为新元古代末期全球处于一个“slush snowball”状态的观点提供了有力支持。There has been a long-standing debate that whether the earth was a"hard snowball"or a"slush snowball"during the Neoproterozoic Marinoan Ice Age.The glacial sediments of the Nantuo Formation from the Liangqiao section of Chengkou,in the Dabashan area,are complete with extensive development,providing an ideal target for studying the Marinoan glacial sedimentary sequence.Geochemical evidence is of great significance for reconstructing the late Neoproterozoic paleoclimate.The petrological characteristics of the Nantuo Formation show that it is predominantly composed of gray-green and gray-purple pebbly siltstone in the Daba Mountain area.The geochemical characteristics of the moraine deposits reveal that the Nantuo Formation in this area underwent low chemical weathering and was in a cold and dry climate.Paleoclimatic indicators,such as the chemical index of alteration(CIA),chemical index of weathering(CIW),and plagioclase index of alteration(PIA),exhibit clear cyclic variations.The gray-purple pebbly siltstone gradually decreases upwards from a high value in the bottom,while the gray-green pebbly siltstone gradually increases from bottom to top starting from a low value,implying multiple cold and warm paleoclimatic fluctuations in the early Nantuo period.Regional correlations and sedimentary patterns of the Nantuo Formation in the Yangtze area indicate that the Nantuo glacial period can be further divided into an early gradual freezing period,a middle frozen period,and a late thawing period.The climatic changes mainly occurred during the early and late Nantuo periods,especially in the shallow-water sedimentary areas.Therefore,evidence from the glacial sedimentary sequence and paleoclimatic variation of the Nantuo Formation supports the hypothesis that the earth was a"slush snowball"at the end of the Neoproterozoic era.

关 键 词：大巴山地区 Marinoan冰期 沉积地球化学 冰川沉积序列 古气候演化 

分 类 号：P532[天文地球—古生物学与地层学]