Devonian–Carboniferous Hangenberg Crisis in South China: Variations in Trace Elements, Strontium and Carbon Isotope Chemostratigraphy in the Nanbiancun Carbonate Section

Abstract

AbstractThe global Hangenberg Crisis or Hangenberg Extinction is a mass extinction near the Devonian–Carboniferous boundary. Comprehensive research of petrology and geochemistry on the Devonian–Carboniferous boundary, as exposed in the Nanbiancun auxiliary stratotype section, South China, elucidates paleoenvironmental changes and controls on marine strontium (87Sr/86Sr) and carbonate carbon (δ13Ccarb) isotopes during the Hangenberg Crisis. The new 87Sr/86Sr data reveal a regression in the Middle Siphonodella praesulcata Zone, while the Hangenberg Extinction was occurring in South China. Moreover, the δ13Ccarb data records a negative excursion near the base of the Middle Siphonodella praesulcata Zone that may have been connected with the Hangenberg Extinction. A positive δ13Ccarb excursion, corresponding with the Upper Siphonodella praesulcata Zone, may reflect the effects of a vigorous biological pump. The magnitude of the Hangenberg Carbon Isotopic Excursion in peak δ13carb values and δ13Ccarb gradient in carbonate Devonian–Carboniferous boundary sections of the South China Craton during the Hangenberg Crisis, are a function of depositional water depth and distance from the shore. The carbon cycling during the Hangenberg Carbon Isotopic Excursion had a much stronger impact on oceanic surface waters than on the deep ocean and the δ13Ccarb gradient of local seawater was likely caused by enhanced marine productivity, associated with biological recovery in platform sediments during the Hangenberg Crisis.