Did ophiolite obduction in the tropics drive global climate? A detrital sediment perspective

Earth's last half-billion years exhibit alternating greenhouse and icehouse climate states, but we do not know why. Global climate state reflects atmospheric CO2 partial pressure, a product of volcanic emission and silicate weathering drawdown, modulated by the biosphere. Global climate simulations on geological timescales show temporal correlation with tectonic collisions. However, collision simultaneously terminates arc volcanism and exposes fresh rock for weathering: these processes are hard to deconvolve.Recent studies have provocatively hypothesised that Earth’s climate state is set by ophiolite obduction in tropical collisions. Here, rapid weathering of reactive rocks efficiently consumes CO2. This hypothesis yields a testable prediction: that the sedimentary archive of ancient tropical orogens will contain ophiolitic detrital minerals at the onset of icehouse periods. Here, we use automated heavy mineral analysis of key sedimentary sections from the New Guinea and Taconic-Grampian orogens to identify and quantify ophiolite detritus. We integrate these data with detrital geochronology and bulk geochemistry to assess ophiolitic weathering contribution to CO2 drawdown.