The Late Devonian represents a critical interval in Earth’s history, marked by multiple bio-events. Among these events, the Annulata Event is a short-term bio-event during the Famennian Age. To investigate the biostratigra phy and chemostratigraphy of the Annulata Event within shallow-water carbonate settings in South China, we con ducted integrated conodont biostratigraphic and stable isotopic analyses on upper Famennian strata at the Shuiyuantou section in Xing’an County, northeastern Guilin, Guangxi. A total of six samples were collected, each yielding abundant conodonts. Thirty-three species (including four undetermined taxa) of seven genera were identified, represented by Bispathodus, Icriodus, Nothognathella, Palmatolepis, Pseudopolygnathus, Polygnathus, and Spathognathodus. A re working process probably occurred, as some conodonts exhibit longer stratigraphic ranges than previously recorded; however, potentially reworked specimens were excluded from the establishment of conodont zonation. The conodont assemblages enable us to establish three conodont biozones, in ascending order: the Palmatolepis rugosa trachytera Zone, the Pseudopolygnathus granulosus Zone, and the Polygnathus styriacus Zone. Although the characteristic or ganic-rich black shales and carbonates associated with the Annulata Event in European and South China are absent at the Shuiyuantou section due to coverage, combined biostratigraphic and carbon isotopic evidence places the lower to middle part of Bed 6 within the Pseudopolygnathus granulosus Zone, correlating it with the Annulata Event horizon. This interval exhibits a pronounced positive carbon isotope excursion. A synthesis of previous data suggests that sea-level rise, enhanced marine primary productivity, and expanded marine anoxia collectively drove the observed carbon cycle perturbations during the Annulata Event.
