Iron Loss During Continental Weathering in the Early Carboniferous Period Recorded by Karst Bauxites

Abstract Significant iron (Fe) loss can occur during continental weathering and efflux to the ocean via runoff, historically affecting global Fe cycling marine ecosystems. Here, we report extremely low content in early Carboniferous (ca. 340 Ma) bauxites southwestern China. These were formed by redeposition of terrestrial soils along paleo‐continental margin western South China Plate warm climates. The contain high δ 56 (−0.17‰ +1.15‰) values with a negative correlation between 2 O 3 Fe, indicating that substantial amount Fe(III) was reduced isotopically light dissolved Fe(II) effuxed reductive dissolution under anoxic conditions. C org HR /Fe T , Mo/Al, U/Al, V/Al ratios bauxite suggest this reduction process occurred pedogenic (continental weathering) rather than depositional/diagenetic stage karst formation. Most rapidly re‐oxidized transported toward forming ores around zero (−0.13‰ +0.16‰). Al contents suggests common processes geological periods favoring formation, such as Carboniferous, Permian, Cretaceous Cenozoic era. Karst may thus provide record act an indicator enhanced flux oceans.