CO2, organic carbon burial, and global climate change in the Wenlock (Silurian):waired 13 Ccarb and 13 Corg analyses of marine carbonates

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The propose of this investigation is to examine the most volatile Series in the Phanerozoic history of the global carbon cycle and the role of CO2 in globale climate change. The Wenlock Series contains two major (+4%) positive carbon isotope excursions (early Wenlock Ireviken Excursion; late Wenlock Mulde Excursion) and both have been associated in the literature with glaciation and global climate change. The role of the carbon cycle and CO2 in global climate change has long been a topic of considerable debate. However, changes in CO2 are most often considered to be the primary driver of Phanerozoic climate change. Recent publications framing this debate have forcused on long-term climate change by comparing various Phanerozoic scale proxy records. Inversitgations to produce high-resolution (sub System scale) records of CO2 change in the Palaeozoic are only just beginning. In the lower Palaeozoic, the most widely accepted method for determining palaeo-¿ CO2 is paired analysis of carbon isotopes in both carbonate and organic carbon. Recent data from North America indicate that a previously unknown negative excursion in ¿ 13Corg coincided with the positive excursion in ¿ 13Corg during the early Wenlock. The data indicate the ¿ CO2 was increasing during the Ireviken positive carbon isotope excursion. This relationship has great implications for Silurian climate/ocean models, but at present is known from only one section globally. Paired isotopic analyses of ¿ 13Ccarb and ¿ 13Corg on the late Wenlock excusion have been carried out so far only on 14 samples on one bore hole. The investigation proposed herein will provide the most comprehensive (both temporally and spatially) record of ¿ CO2 and organic carbon burial of any Series in the lower Palaeozoic. This will be accomplished in two steps: 1) high-resolution (100,000 years per sample) carbonate carbon (¿ 13Ccarb) isotope stratigraphy 2) paired carbonate and organic carbon (¿ 13Ccarb and ¿ Corg) isotope stratigraphy of the Wenlock Series from sections globally. As the Wenlockian isotope excursions have many conspicuous similarities (geochemial, sedimentological, and palaeontological) with other Early Palaeozoic isotope excursions we expect new insights into the climate systems not only for the Wenlock but for the whole Early Palaeozoic.