Tectonic fragments subjected to high-pressure metamorphism in the Alps contain up to 1 vol% each of dolomite and graphite, indicating that significant amounts of carbon-bearing sediment were transported to depths greater than 50 km during the Alpine orogeny. The absence of a Cretaceous-Tertiary volcanic arc on the overriding plate suggests that much of the subducted carbon remains at depth today. Averaged over the length of the Alpine chain and the estimated amount of subduction that occurred in the past 125 m.y., ∼1016 kg of carbon was buried because of collision in the Alpine region. Additional consideration of the Himalayan chain suggests that more than 1017 kg of carbon has been buried since 125 Ma by continent-continent collision. Transfer of this amount of carbon from atmospheric and sedimentary reservoirs into a deep-seated metamorphic reservoir may help explain the significant decrease in global surface temperature that occurred from 125 Ma to the present.

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