Silurian to Early Triassic Magnetic Susceptibility Variations in the South Yellow Sea and Their Environmental Implications: Records From the CSDP-2 Well

Abstract

Until recently, no physical rock samples from the Palaeozoic to Mesozoic eras had been recovered from the South Yellow Sea (SYS), leaving the palaeoclimatic significance of this period largely unexplored. This study analyzes data from the Lower Silurian to Lower Triassic strata of the CSDP-2 Well, including magnetic susceptibility (MS) data from 251 samples and geochemical element data for 345 samples, to determine environmental changes and their implications. We successfully establishes vertically continuous and complete MS and geochemical curves within the SYS, and two depth segments with anomalous values and four climatic shifts are identified. Through the coupled analysis of MS and geochemical data, along with the synthesis of previously published data, one anomalous segment from 1690-2006. 9 meters below sea floor (mbsf) could represent the Late Devonian-Early Permian Ice Age, which lasted approximately 80 Ma. Another segment from 820-930 mbsf represents Emeishan and Siberian volcanism, with an interval between the two events spanning approximately 2.7 Ma. And 15 variation cycles are identified by analyzing changes of MS values, we found that geological event cycles spanned 3-9 Ma during the Early Silurian to Permian, but the interval shorten to approximately 28.6 Kyr in the Early Triassic. In summary, the CSDP-2 Well records several significant geological events and the SYS underwent an exceptionally complex evolution of geological environments during the Early Mesozoic. Additionally, MS data from CSDP-2 Well reveal unique variation patterns not seen in adjacent areas or other blocks, indicating that while the SYS was influenced by global climate and tectonic activities at block-level, it also experienced distinct regional geological environmental changes.