Orbital control on cyclical organic matter accumulation in Early Silurian Longmaxi Formation shales  

作　　者：Siding Jin Hucheng Deng Xing Zhu Yan Liu Sibing Liu Meiyan Fu 

机构地区：[1]State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development,Beijing 100083,China [2]College of Energy,Chengdu University of Technology,Chengdu 610059,China [3]College of Environment and Civil Engineering,Chengdu University of Technology,Chengdu 610059,China

出　　处：《Geoscience Frontiers》2020年第2期533-545,共13页地学前缘（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 41802030);National Science and Technology Major Project (Grant Nos. 2017ZX05036-004-006 and 2016ZX05036-003007)

摘　　要：High resolution(939 samples)total organic carbon content(TOC)analyses were conducted on the Shuanghe Section of^152.6 m in the Changning area,Sichuan Basin.The sampling section was divided into two units considering the distinct-different deposit environment and sediments accumulation rate.The lower part(Unit 1)and the peer part(Unit 2)with high resolution sample spacing(0.08–0.4 m)enables the identification of the precession cycle in two sedimentary sequences with distinct different sedimentary accumulation rate.MTM Power spectral analyses on untuned TOC series reveals significant peaks exceeding above the 95%confidence level and shows that both Unit 1 and Unit 2 have recorded Milankovitch cycles of 405 kyr long eccentricity,short eccentricity,obliquity and precession.The floating astronomical time scale(ATS)was constructed on the Shuanghe Section in the Early Silurian(~439.673–444.681 Ma),and which was calibrated by 405 kyr long eccentricity cycles.The total duration of the Wufeng and Longmaxi shales is 5.01 Myr.The floating ATS used for estimating the duration of the graptolite zones and each stage in the study interval.Finally,we postulated two models that could verify the linkage between orbital cycle and organic accumulation.To make sure whether productivity or preservation is the main factor that under long eccentricity control,the phase correlation between the obtained filtered signal and the theoretical orbital solution should be made clear in the further research.High resolution(939 samples) total organic carbon content(TOC) analyses were conducted on the Shuanghe Section of～152.6 m in the Changning area,Sichuan Basin.The sampling section was divided into two units considering the distinct-different deposit environment and sediments accumulation rate.The lower part(Unit 1)and the peer part(Unit 2) with high resolution sample spacing(0.08-0.4 m) enables the identification of the precession cycle in two sedimentary sequences with distinct different sedimentary accumulation rate.MTM Power spectral analyses on untuned TOC series reveals significant peaks exceeding above the 95% confidence level and shows that both Unit 1 and Unit 2 have recorded Milankovitch cycles of 405 kyr long eccentricity,short eccentricity,obliquity and precession.The floating astronomical time scale(ATS) was constructed on the Shuanghe Section in the Early Silurian(～439.673-444.681 Ma),and which was calibrated by 405 kyr long eccentricity cycles.The total duration of the Wufeng and Longmaxi shales is 5.01 Myr.The floating ATS used for estimating the duration of the graptolite zones and each stage in the study interval.Finally,we postulated two models that could verify the linkage between orbital cycle and organic accumulation.To make sure whether productivity or preservation is the main factor that under long eccentricity control,the phase correlation between the obtained filtered signal and the theoretical orbital solution should be made clear in the further research.

关 键 词：CYCLOSTRATIGRAPHY Floating astronomical time scale Early Silurian Organic matter accumulation 

分 类 号：P534.43[天文地球—古生物学与地层学] P59[天文地球—地质学]