The Cretaceous/Paleogene (K/Pg) boundary is one of the most important mass extinction crisis during the Phanerozoic. Caused by the volcanism of Deccan trapps and/or the impact of a meteorite, this mass extinction had a disastrous impact on calcareous nannofossils diversity leading to the most important turnover in their evolutionary history. The K/Pg mass extinction led also to an important change in the pelagic carbonate production and accumulation which has deeply perturbed the carbonate system. In this study, we aim to quantify nannofossil carbonate accumulation rates before and after the K/Pg boundary to discuss i) the impact of the volcanism on calcareous nannofossil size and carbonate production; ii) the impact of the mass extinction event s.s. on the pelagic carbonate accumulation rate and iii) the timing of recovery of a stable and efficient pelagic carbonate production and accumulation after the crisis. Ultimately, we aim to estimate the impact of the K/Pg mass extinction on the carbonate and carbon cycles. Three deep-sea drilling sites were studied: ODP Site 762C from the Eastern Indian Ocean, IODP Site 1209 from the Northwestern Pacific Ocean and IODP Site 1267 from the Southeastern Atlantic. These sites have been precisely dated by cyclostratigraphy and biostratigraphy (Husson et al., 2011; Westerhold et al., 2011; Dinarès-Turell et al., 2014) and presents continuous sedimentation in the studied interval. We studied around 100 samples by site covering about 3 Myr before and 3 Myr after the K/Pg boundary. On each sample, the total carbonate content was measured and its accumulation rate estimated. We performed biometry of nannofossils (size and mass) in order to trace the morphometric variability of nannofossil and species specific carbonate accumulation rates through the K/Pg boundary. References Dinarès-Turell, J., Westerhold, T., Pujalte, V., Röhl, U. and Kroon, D., 2014. Astronomical calibration of the Danian stage (Early Paleocene) revisited: Settling chronologies of sedimentary records across the Atlantic and Pacific Oceans, Earth and Planetary Science Letters, 405: 119-131. Husson, D., Galbrun, B., Laskar, J., Hinnov, L.A., Thibault, N., Gardin, S. and Locklair, R.E., 2011. Astronomical calibration of the Maastrichtian (Late Cretaceous). Earth and Planetary Science Letters, 305: 328-340. Westerhold, T., Röhl, U., Donner, B., McCarren, H.K. and Zachos, J.C., 2011. A complete high-resolution Paleocene benthic stable isotope record for the central Pacific (ODP Site 1209), Paleoceanography, 26: PA2216.