2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 328-9
Presentation Time: 4:00 PM

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


CHEN, Jitao1, MONTAÑEZ, Isabel P.1, QI, Yuping2, WANG, Xiangdong2, WANG, Qiulai2 and LIN, Wei2, (1)Department of Earth and Planetary Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, (2)Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China, jitaochen@126.com

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.