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

The 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 (Sr-87/Sr-86) and carbonate carbon (delta C-13(carb)) isotopes during the Hangenberg Crisis. The new Sr-87/Sr-86 data reveal a regression in the Middle Siphonodella praesulcata Zone, while the Hangenberg Extinction was occurring in South China. Moreover, the delta C-13(carb) 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 delta C-13(carb) 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 delta(13)(carb) values and delta C-13(carb) 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 delta C-13(carb) gradient of local seawater was likely caused by enhanced marine productivity, associated with biological recovery in platform sediments during the Hangenberg Crisis.