塔里木盆地奥陶系萨尔干组旋回地层学研究  

Cyclostratigraphy of the Ordovician Saergan Formation in the Tarim Basin

作　　者：高源 任传真 房强[1,2,3] 吴怀春[1,2,3] 时美楠[1,2,3] 张世红[1,2] 杨天水[1,2] 李海燕[1,2] GAO Yuan;REN ChuanZhen;FANG Qiang;WU HuaiChun;SHI MeiNan;ZHANG ShiHong;YANG TianShui;LI HaiYan(State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Beijing 100083,China;Frontiers Science Center for Deep-time Digital Earth,China University of Geosciences(Beijing),Beijing 100083,China;Key Laboratory of Polar Geology and Marine Mineral Resources,School of Ocean Science,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质大学(北京)生物地质与环境地质国家重点实验室,北京100083 [2]中国地质大学(北京)深时数字地球前沿科学中心,北京100083 [3]中国地质大学(北京)海洋学院极地地质与海洋矿产教育部重点实验室,北京100083

出　　处：《沉积学报》2025年第1期88-98,共11页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41925010,42072039)。

摘　　要：【目的】中—上奥陶统萨尔干组是一套在塔里木盆地广泛分布的海相烃源岩,其沉积模式尚不明确。高分辨率地质年代学的约束有助于精确刻画萨尔干组沉积过程。【方法】对新疆阿克苏市柯坪地区苏巴什沟剖面长度为9.0 m的萨尔干组进行质量磁化率测试,并利用获得的701个数据进行详细的旋回地层学分析。【结果】通过频谱分析识别出0.741~1.283 m、0.204~0.267m、0.057~0.071 m和0.035~0.039 m的显著谱峰,其比例约为21.14∶7.71∶5.71∶1.86∶1.11∶1,与中—晚奥陶世天文轨道旋回周期的比值相近。利用405 ka长偏心率旋回的周期进行天文校准,得到短偏心率、斜率和岁差旋回的周期分别为100 ka、30.6~31.2 ka和20.0~21.8 ka。利用识别出的长偏心率旋回建立了研究剖面持续时间为~3.9 Ma的“浮动”天文年代标尺。以Nemagraptus gracilis笔石带底界作为等时界面,实现了苏巴什沟剖面和大湾沟剖面(上奥陶统底界全球辅助层型剖面)在405 ka时间尺度上的旋回地层对比,计算出苏巴什沟剖面萨尔干组开始沉积的时间比大湾沟剖面晚约1.03 Ma。【结论】上述研究支持萨尔干组形成于逐步海侵过程。此外,~1.2 Ma的超长斜率旋回可能控制着萨尔干组沉积期的海平面变化。[Objective]The Middle-Upper Ordovician Saergan Formation in the Tarim Basin represents an important hydrocarbon source rock deposited in a marine environment.However,the current model of the deposition of the Saer-gan Formation remains nebulous.High-precision geochronologic constraints may shed new light on the deposition his-tory of the Saergan Formation.[Methods]The identification of Milankovitch cycles,in particular,a 405 ka long or-bital eccentricity cycle,can be used to construct precise time scales for the sedimentary succession of the Paleozoic Era.The magnetic susceptibility(MS)is a measure of the degree of magnetization of a material in response to an ap-plied magnetic field,which can be a powerful tool for cyclostratigraphy and paleoclimate studies.Here,a total of 701 MS measurements from the 9 m Saergan Formation in the Subashigou section of the Kalpin area,Aksu city,Xinjiang were obtained to conduct a cyclostratigraphic analysis,including a multitaper method spectral analysis,an evolutive harmonic analysis,and bandpass filtering.[Results]The spectral analyses show significant peaks at 0.74-1.28 m,0.2-0.27 m,0.057-0.071 m,and 0.035-0.039 m with ratios of 21.14∶1,7.71∶1,5.71∶1,1.86∶1,and 1.11∶1,which are close to those of the Middle-Late Ordovician astronomical cycles.Although there is no reliable astronomical solution for the Ordovician period,astronomical calibration can be achieved using a stable 405 ka eccentricity cycle.After the 405 ka long eccentricity calibration,the spectral analysis shows periods with 100 ka(short eccentricity),30.6-31.2 ka(obliquity),and 20-21.8 ka(precession).Ten eccentricity cycles are obtained using bandpass filtering and a“floating”astronomical time scale with a duration of~3.9 Ma is established for the Saergan Formation of the Subashigou section.An amplitude modulation(AM)envelope of the interpreted 30.6 ka band of the 405 ka calibrated MS time series reveals long-term cycles with a period of~1.2 Ma for the Ordovician,which is identical with that at present

关 键 词：塔里木盆地 中—上奥陶统 旋回地层对比 1.2 Ma斜率旋回 沉积模式 

分 类 号：P534.42[天文地球—古生物学与地层学]