Novel porphyrins as molecular fossils for anoxygenic photosynthesis

The iron porphyrin fraction of Kupferschiefer, an organic-rich sedimentary rock deposited in the Zechstein Sea during the Permian (ca. 235Myr before present) contains three minor components characterised by 1 H NMR spectroscopy. The carbon skeletons correlate specifically with members of one series of the bacteriochlorophylls d of the Chlorobiaceae, which are obligate anaerobes. Their structures therefore reveal the occurrence of anoxic conditions extending up into the zone of light penetration in the water column of the original depositional setting in the Lower Rhine Basin.