LATE PALEOZOIC IRON FERTILIZATION FROM DUST ENHANCED SHALLOW MARINE PRIMARY PRODUCTIVITY

The importance of dust as a source of iron (Fe) for marine primary production in modern oceans is well studied but remains poorly explored for deep time. Vast dust deposits are well recognized from the late Paleozoic, and provisionally implicated to drive biotic production through iron fertilization. Here, we document dust impacts on marine primary productivity in Moscovian (Middle Pennsylvanian, ~307 Ma) and Asselian (Lower Permian, ~295 Ma) carbonate strata from peri-Gondwanan terranes of Iran, at southern mid paleo-latitudes. Fossil community composition of both intervals shifted with Fe_HR/Fe_T in samples as shown by significant correlations between PCoA axis scores and Fe_HR/Fe_T. Autotrophic content of samples, detected by both point counting and lipid biomarker analysis, track concentrations of highly reactive Fe, consistent with the hypothesis that dust stimulated marine primary productivity, also promoting carbonate precipitation. Additionally, highly reactive Fe positively tracks the volume of the finest dust fraction. Consequently, dust likely stimulated both organic and inorganic carbon cycling, helping to maintain low pCO₂ even as terrestrial repositories for organic carbon (peat/coal) diminished from the Carboniferous through Permian.