Li and Si isotopes reveal authigenic clay formation in a palaeo-delta

Marine authigenic clay formation has long been postulated as a major process to explain the mass budgets of some elements in seawater, and might act reverse reaction for neutralization atmospheric acidity by soil forming reactions on land. Nevertheless, date, handful studies have directly investigated effect weathering due challenges associated with sampling complexity. Deltas are thought be one possible environments where may occur because abundant influx derived materials dynamic activities. In this study, we use unique combination three isotope systems (Si, Li, Nd) evidence using sediments collected from ?40 Ma-old delta complex (Ainsa Basin, Spain). Sediments were along land sea depositional continuum, alluvial coastal plains marine environments. Direct comparison between alluvial, coastal, allows observing potential weathering. Systematic differences Si Li composition exist continental sediments, revealing an phase sequestrating light diagenesis Fe reducing deltaic Finally, study proposes geochemical tool helping distinguishing origins sedimentary rocks when lithofacies biofacies prove ineffective.