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Maleimide index: a paleo-redox index based on fragmented fossil-chlorophylls obtained by chromic acid oxidation
Kenta Asahina1, Satoshi Takahashi2, Ryosuke Saito3,4
1Research Institute for Geo-Resources and Environment, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST) Central 7, 1-1-1 Higashi Tsukuba Ibaraki 305-8567 Japan kenta-asahina@aist.go.jp +81-29-861-2391.
Abstract:
The composition of past photosynthetic organisms provides information about the paleo-environment based on the habitat characteristics of photosynthetic organisms. Therefore, analysis of chlorophyll-derived materials from photosynthetic organisms in sedimentary rocks is important for understanding paleo-environmental changes. Fossilized chlorophylls present in sedimentary rocks can be detected by their conversion into maleimides and phthalimides. This can be achieved through the chromic acid oxidation of sedimentary rocks. Since the maleimides and phthalimides are derived from the pyrrole skeleton of fossil chlorophylls, their composition reflects the composition of paleo-photosynthetic organisms. We herein propose an indicator for detecting anoxic-sulfidic conditions in the paleo oceanic photic zone, which is based on the composition ratio of the maleimides produced during the oxidation process. The maleimide index in this study would be a useful analytical method to indicate that anoxic-sulfidic conditions in the paleo oceanic photic zone, which is associated with mass extinction events, have occurred.
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