Silicate weathering, land plants and cooling in the late Silurian and early Devonian

The development of terrestrial vegetation and its impact on silicate weathering is hypothesized to have driven multiple cooling events throughout the Paleozoic. One such event is the 8–10°C cooling observed from the late Silurian to early Devonian ( c . 420–385 Ma). Chemical weathering of Ca- and Mg-bearing silicate minerals and the subsequent trapping of carbon in marine carbonates are a sink for atmospheric CO 2 on multimillion-year time scales. The strontium isotopic ratio ( 87 Sr/ 86 Sr) of seawater acts as a geochemical proxy for this process. In this study, we present new Silurian to Devonian 87 Sr/ 86 Sr data paired with oxygen isotopes ( δ 18 O; a proxy for palaeotemperature and ice volume) from conodont apatite. The two datasets show an inflection in the late Silurian to early Devonian, suggesting a connection between enhanced basaltic weathering (leading to lower 87 Sr/ 86 Sr) and cooling (increasing δ 18 O). The spread of terrestrial plants probably drove a significant portion of the enhanced basaltic weathering, which would have driven cooling, in addition to coeval tectonic changes in the Pridoli Epoch (422.7–419.0 Ma) and Lochkovian Age that further enhanced weathering and drawdown of atmospheric CO 2 (419.0–412.4 Ma).