Four hierarchical cyclothems, superbundlesets, bundlesets, bundles and laminae, have been identified from the Devonian Frasnian-Famennian carbonate strata in Guangxi, South China. Their hierarchical structures, ratio ...Four hierarchical cyclothems, superbundlesets, bundlesets, bundles and laminae, have been identified from the Devonian Frasnian-Famennian carbonate strata in Guangxi, South China. Their hierarchical structures, ratio relationships and sequence in conodont zones are continuous and stable and can be traced across different facies zones and sedimentary basins. Our data show that hierarchically organized superbundlesets, bundlesets, bundles and laminae correspond to the long eccentricity, eccentricity, obliquity or precession and sub-Milankovitch cycles respectively. Their periods were 400,000, 100,000, 33,333, 16,667 and 8,000–17,000 a, respectively. The ratios of long eccentricity to eccentricity, eccentricity to obliquity, and eccentricity to precession in the Devonian are 1:4, 1:3 and 1:6 respectively. Using these hierarchical Milankovitch cyclothems, chronostratigraphical division and correlation can be realized at a resolution of 100 ka or 10 ka at the Frasnian-Famennian transition. The time intervals of the Upper rhenana Zone, linguiformis Zone, and the Lower, Middle and Upper triangularis Zone are 0.6, 0.8, 0.3, 0.3 and 0.3 Ma, respectively. Sea-level changes of the Frasnian-Famennian transition were not coherent and synchronous at the resolution of 100 ka or 10 ka in the basin-slope carbonate sequences of Guangxi, South China.展开更多
基金The study was jointly supported by the National Natural Science Foundation of China(Grants 49472086 and 40072041)the Ministry of Science and Technology(the SSER project).
文摘Four hierarchical cyclothems, superbundlesets, bundlesets, bundles and laminae, have been identified from the Devonian Frasnian-Famennian carbonate strata in Guangxi, South China. Their hierarchical structures, ratio relationships and sequence in conodont zones are continuous and stable and can be traced across different facies zones and sedimentary basins. Our data show that hierarchically organized superbundlesets, bundlesets, bundles and laminae correspond to the long eccentricity, eccentricity, obliquity or precession and sub-Milankovitch cycles respectively. Their periods were 400,000, 100,000, 33,333, 16,667 and 8,000–17,000 a, respectively. The ratios of long eccentricity to eccentricity, eccentricity to obliquity, and eccentricity to precession in the Devonian are 1:4, 1:3 and 1:6 respectively. Using these hierarchical Milankovitch cyclothems, chronostratigraphical division and correlation can be realized at a resolution of 100 ka or 10 ka at the Frasnian-Famennian transition. The time intervals of the Upper rhenana Zone, linguiformis Zone, and the Lower, Middle and Upper triangularis Zone are 0.6, 0.8, 0.3, 0.3 and 0.3 Ma, respectively. Sea-level changes of the Frasnian-Famennian transition were not coherent and synchronous at the resolution of 100 ka or 10 ka in the basin-slope carbonate sequences of Guangxi, South China.
