闽西永安盆地白垩纪古气候演化及其对华南沿海地貌变化的响应  

Cretaceous paleoclimate evolution of Yong'an Basin in western Fujian and its response to geomorphic changes along the coast of South China

作　　者：何岸北 朱作飞 赵奇 HE Anbei;ZHU Zuofei;ZHAO Qi(Key Laboratory of Ocean and Marginal Sea Geology,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;Center for Excellence in Deep Earth Science,Chinese Academy of Sciences,Guangzhou 510640,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Faculty of Geography,Yunnan Normal University,Kunming 650500,China;Sanya Institute of South China Sea Geology,Guangzhou Marine Geological Survey,Sanya 572025,China)

机构地区：[1]中国科学院广州地球化学研究所,边缘海与大洋地质重点实验室,广州510640 [2]中国科学院深地科学卓越创新中心,广州510640 [3]中国科学院大学地球与行星科学学院,北京100049 [4]云南师范大学地理学部,昆明650500 [5]广州海洋地质调查局三亚南海地质研究所,三亚572025

出　　处：《海洋地质前沿》2024年第12期50-63,共14页Marine Geology Frontiers

基　　金：国家自然科学基金委(NSFC)-广东联合基金“华南陆壳结构与南海北部地质过程研究”(U1701641);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项“南海北部陆缘岩石圈薄化-破裂过程及其资源效应”(GML2019ZD0205)。

摘　　要：以永安盆地白垩系坂头组、沙县组、崇安组为研究对象,采集细碎屑岩样品进行了主微量元素及稀土元素测试,并与其沉积特征、古生物化石特征进行对比分析,探究白垩纪时期福建西部永安盆地的古气候演化特征,结合华南东南缘古气候变化,探讨二者与华南沿海中生代晚期地貌变化的关系。结果显示,下白垩统坂头组地层样品CIA值为69.91~85.29、Rb/Sr值为1.13~2.21、Mg/Ca值为0.57~3.57、Sr/Cu值为5.44~11.66、校正后古盐度指标100*Sr/(Ba^(*)Al_(2)O_(3))值为1.18~1.55,表明该区早白垩世早期气候由温暖湿润转为干旱炎热;δCe值为0.89~1.03、V/Cr值为1.03~1.57、Ni/Co值为2.34~10.58,表明早白垩世早期主要为弱氧化环境,间接指示该区当时气候由温湿向干热转变。早白垩世晚期以来,沙县组和崇安组地层样品的测试结果显示,CIA值为67.14~75.68、Rb/Sr值为0.99~9.05、Mg/Ca值为0.37~16.22、Sr/Cu值为1.20~15.46、以及校正的古盐度指标100^(*)Sr/(Ba^(*)Al_(2)O_(3))值为0.50~1.77,指示永安盆地早白垩世晚期以来气候由干旱炎热向温暖湿润再向干旱寒冷变化;由δCe(0.89~1.03)、V/Cr值(0.51~1.72)、Ni/Co值(1.45~6.45)可以看出,早白垩世晚期以来弱氧化、弱还原环境交替出现,间接证明该区域自早白垩世晚期以来气候发生了多重转变,从干旱炎热到温暖湿润再到干旱寒冷。综上情况可以推断,永安盆地白垩纪期间古气候出现温暖湿润—干旱炎热—温暖湿润—干旱寒冷(伴有极端气候)多次转化。将研究区与周缘华南地区古气候进行统计对比,发现华南内陆古气候以温暖湿润向干旱炎热转变为主,华南沿海与内陆古气候转变的差异是对晚中生代华南沿海地貌变化的响应。To explore the evolution characteristics of the Cretaceous paleoclimate in the Yong'an Basin in western Fujian and the influence of the Late Mesozoic geomorphic changes along the coast of South China on the paleoclimate in the southeastern margin of South China,the Cretaceous stratigraphy of the Bantou,Shaxian,and Chong'an formations in the basin was taken as the research object.The fine-grained clastic rock samples were collected and examined for major and trace elements and rare earth elements distributions,and their sedimentary and paleontological characteristics were compared and analyzed.Variations in the paleoclimate of the Yong'an Basin in western Fujian during the Cretaceous period were clarified.Results show that the early Cretaceous Bantou Formation reflects a changing climate condition.The value ranges of CIA(chemical index of alteration)(69.91~85.29),Rb/Sr(1.13~2.21),Mg/Ca(0.57~3.57),Sr/Cu(5.44~11.66),and the calibrated paleosalinity index [100^(*)Sr/(BaAl_(2)O_(3))](CPI)(1.18~1.55) collectively suggest a scheme transition from a warm-humid climate to a dry-hot environment.Moreover,the redox discrimination indices δCe(0.89~1.03),V/Cr(1.03~1.57),and Ni/Co(2.34~10.58) signaled a dominant weak oxidation environment,aligning with the transition to dry-hot climate in the early Cretaceous.Moving to the late Early Cretaceous to Late Cretaceous,Shaxian Formation and Chong'an Formation samples manifest further shifts in climate dynamics.The value ranges of CIA(67.14~75.68),Rb/Sr(0.99~9.05),Mg/Ca(0.37~16.22),Sr/Cu(1.20~15.46),and CPI(0.50-1.77) expose a change from hot-dry to warm-humid,followed by a transition to cold-dry climate.The δCe value(0.89~1.03),V/Cr(0.51~1.72),and Ni/Co(1.45~6.45) point to alternating weak oxidation and weak reduction environments,aligning with the multiple climate shifts during this period.Therefore,the Cretaceous paleoclimate of the Yong'an Basin exhibits a complex transitional sequence in climate,oscillating from dry-hot to warm-humid and then to drycold conditions,often with ex

关 键 词：闽西 白垩纪 华南沿海 古气候 古地貌 地球化学 

分 类 号：P595[天文地球—地球化学] P736[天文地球—地质学]