--> Organic Carbon Isotopes From Halites: A New Approach to Studying Evaporite Sequences

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Organic Carbon Isotopes From Halites: A New Approach to Studying Evaporite Sequences

Abstract

Despite the fact that evaporite deposits provide reservoir seals for over half of the world's petroleum reserves, they are notoriously challenging to investigate, from both a sequence stratigraphic and paleoenvironmental context. Since almost all marine organisms are absent in these deposits, obtaining a high degree of temporal constraint and understanding the mechanistic controls on large-scale deposition in evaporitic basins presents a significant challenge. More specifically, without adequate temporal constraint, it is nearly impossible to assess: (i) eustacy; (ii) local and/or global mechanisms controlling paleoclimate change and mass extinction; and (iii) the timing and lithostratigraphic relationships of various economically valuable evaporite deposits. Here, we present a novel approach for studying evaporitic basins whereby the challenge presented by a lack of biostratigraphic data becomes surmountable when the evaporite deposits are temporally linked with global perturbations in the carbon cycle. To demonstrate this approach, we have generated an organic carbon isotope curve from bulk organic matter within the halite-dominate deposits in the Silurian Salina Group, Michigan Basin. These data show that long-term trends in the carbon isotope curve across the Niagaran / Salina groups, which represent a sedimentary transition from carbonate to evaporites, agree with coeval global inorganic carbon isotope records. This dataset provides an insight into understanding global paleoenvironmental change and local lithostratigraphic relationships within the Michigan Basin. A carbon isotope approach to studying evaporitic basins helps develop our understanding of the evolution of evaporitic basins in terms of sea level and paleogeography that can further help to develop more accurate exploration strategies of numerous evaporative basins and deposits worldwide.