Analyses of high carbon number geoporphyrins from Boscan oil (Cretaceous W. Venezuela) indicate that there are many isomers present, and that there are at least two sites of extended >C2) alkylation on the porphyrin macrocyc1e. There is tentative evidence that DPEP porphyrins with large isocyclic rings are abundant. Evidence for a novel series of benzo porphyrins without ethyl groups is also presented. MS/MS studies on the porphyrins from Gafsa Basin chert (Paleocene, Tunisia) indicates the presence of benzo DPEP porphyrins in their metal free state.
