In a study published in Science Advances, scientists have used new lithium isotope (δ7Li) data to show that continental clay export promoted organic carbon burial and thus atmospheric oxygenation during the Cambrian period. Animals depend on oxygen for respiration. Thus, the emergence and proliferation of early animals from the late Neoproterozoic to the early Paleozoic era (~600–500 million years ago or mya) has traditionally been attributed to a significant increase in marine oxygen levels. However, geochemical tracers and numerical models suggest that both atmospheric and marine oxygen levels during the Late Neoproterozoic–Early Paleozoic were significantly lower than today, with highly variable marine redox states. During this period, marine oxygenation occurred under conditions of low atmospheric oxygen, attributed to an enhanced marine biological pump. However, the role of other factors, such as the mineral carbon pump promotion of organic matter burial by mineral protection, has not been thoroughly explored for this epoch. To address this gap, Prof. Wei Guangyi of Nanjing University and Prof. Zhao Mingyu of the Institute of Geology and Geophysics of the Chinese Academy of Sciences (IGGCAS), together with their collaborators, developed d7Li in marine siliciclastic sediments, such as mudstones, to track the proportions of continentally derived clays preserved in continental shelf sediments. During chemical weathering, isotopically light lithium is preferentially taken up by secondary silicate minerals (i.e., clays), resulting in more negative d7Li values in highly weathered products. In contrast, primary silicate minerals and weakly weathered products (e.g., feldspar and mica) exhibit higher d7Li signatures similar to those of the average upper continental crust. In addition, marine authigenic clays formed by marine reverse weathering generally exhibit higher d7Li values due to seawater-derived lithium. Therefore, the... |