COUPLED SEDIMENTARY AND δ13C RECORDS OF LATE MISSISSIPPIAN PLATFORM-TO-SLOPE SUCCESSIONS FROM SOUTH CHINA: INSIGHT INTO δ13C CHEMOSTRATIGRAPHY

Widespread incomplete successions and strong endemism of index fossils hinder regional to global stratigraphic correlation of the Visean-Serpukhovian (V–S) boundary interval (late Mississippian) and thus geological interpretation with respect to initiation of the late Paleozoic ice age. We integrate high spatial-resolution δ¹³C time series with detailed sedimentary facies analysis of late Visean-early Serpukhovian carbonate platform-to-slope successions from South China to evaluate the influence of local depositional and diagenetic processes on δ¹³C values and to resolve this correlation issue. Analysis of 11 sedimentary facies from 5 outcrop sections indicates a restricted platform setting (Yashui section) dominated by bioclastic wacke-packstone to lime mudstone in which paleokarst developed, and carbonate slope settings dominated by thin-bedded lime mudstones intercalated with calciturbidites and slump deposits. Based on vertical facies assemblages, three depositional units are recognized, recording a significant sea-level drawdown across the V–S boundary. Multiple negative δ¹³C excursions (>1‰) can be correlated across the V-S boundary interval in several of the slope sections (Naqing, Luokun, and Narao sections). The negative δ¹³C excursions in the Dianzishang section are less distinct; the one above the V-S boundary is absent, likely recording submarine erosion by slumping. A truncated δ¹³C shift by 1.6‰ in the carbonate overlying the paleokarst in the Yashui platform section records the magnitude of carbonate removal during the sea level driven karstification. An overall negative δ¹³C shifts in the Serpukhovian interval of the Yashui section likely records local influences on carbon cycling in the restricted platform setting. This negative δ¹³C trend and associated depositional facies at the Yashui section can be correlated to those from Arrow Canyon section, USA, which, together with other coeval global sedimentary and geochemical records, indicate a widespread eustatic drawdown with initial buildup of the Gondwanan ice sheet. It is suggested that integrated sedimentary facies analysis and δ¹³C chemostratigraphy can be useful for stratigraphic correlation when interpreted within a detailed sedimentary and C isotope regional framework.