|Lithium isotope history of Cenozoic seawater: changes in silicate weathering and reverse weathering|Misra, S.; Froelich, P.N. (2012). Lithium isotope history of Cenozoic seawater: changes in silicate weathering and reverse weathering. Science (Wash.) 335(6070): 818-823. http://dx.doi.org/10.1126/science.1214697
In: Science (Washington). American Association for the Advancement of Science: New York, N.Y. ISSN 0036-8075; e-ISSN 1095-9203, meer
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Weathering of uplifted continental rocks consumes carbon dioxide and transports cations to the oceans, thereby playing a critical role in controlling both seawater chemistry and climate. However, there are few archives of seawater chemical change that reveal shifts in global tectonic forces connecting Earth ocean-climate processes. We present a 68-million-year record of lithium isotopes in seawater (delta Li-7(SW)) reconstructed from planktonic foraminifera. From the Paleocene (60 million years ago) to the present, delta Li-7(SW) rose by 9 per mil (parts per thousand), requiring large changes in continental weathering and seafloor reverse weathering that are consistent with increased tectonic uplift, more rapid continental denudation, increasingly incongruent continental weathering (lower chemical weathering intensity), and more rapid CO2 drawdown. A 5 parts per thousand drop in delta Li-7(SW) across the Cretaceous-Paleogene boundary cannot be produced by an impactor or by Deccan trap volcanism, suggesting large-scale continental denudation.