Special Issue on Neoproterozoic–Paleozoic Ocean Chemistry

This special issue is based on a theme session convened at the Annual Meeting of the Geological Society of America held in Denver, Colorado, in October 2004. The theme session brought together a diverse group of scientists interested in the chemistry of Precambrian and Paleozoic oceans and its role in climatic and evolutionary events. The contributors to this issue make use of a wide range of isotopic (Sr, Ccarb, Corg, O), elemental (Mo, P, Fe, Mn), and organic (TOC) proxies to study the chemistry of Neoproterozoic and Paleozoic oceans. The contributions include stable isotopic studies working to define secular curves for regional and global correlations (Dilliard et al., Katz et al., Wynn and Read, Halverson et al.), new applications of isotopic and elemental ratios from marine facies to determine paleoatmospheric oxygen and carbon dioxide levels (Algeo and Ingall; Cramer and Saltzman), an analysis of links between the long-term carbon and sulfur cycles through the Paleozoic (Gill et al.), use of stable isotopic and trace–element ratios to determine paleoproductivity (Brand et al.), investigation of Mo–TOC relationships in Devonian black shales as a record of paleohydrographic variation (Algeo et al.), and a comparison of bulk rock and component data as seawater proxies (Batt et al.). The papers are listed in stratigraphic order from the Neoproterozoic to the Pennsylvanian. Halverson and others propose a composite, global Sr/Sr chemostratigraphy for the Neoproterozoic that is linked to a high-resolution carbon isotopic profile. Five relatively complete, partly overlapping successions with good carbon isotopic chemostratigraphy form the main structure of the curve. The main structure of the Sr/Sr curve is similar to previous compilations – most of the Neoproterozoic is characterized by a systematic rise in Sr/Sr. Inflections in the Sr/Sr curve generally correspond to carbon cycle perturbations as measured by δC excursions, although the relationship between C and Sr isotopic records appears to be more complex than