Shifting carbonate burial between oceanic and continental crust across Earth history

• Carbonates on oceanic crust cycle quickly but can persist on continental crust. • Most CaCO 3 burial in the Precambrian may have taken place on oceanic crust. • CaCO 3 burial shifted up onto continents during the Ediacaran-Cambrian transition. • CO 2 input from subducting carbonates likely decreased throughout the Paleozoic. • Latest Paleozoic ocean was poorly buffered against effects of CO 2 injections. Chemical weathering fluxes determine carbonate burial rates on geologic timescales, but the locus of carbonate burial is sensitive to tectonic and biologic boundary conditions that have changed across Earth history. Depositional setting is important because sediments on oceanic crust are readily recycled on the timescale of seafloor subduction, whereas sediments on continental crust can be sequestered over much longer durations. Here we present records of carbonate abundance in continental sediments for the past 3600 million years based on the North American components of the Macrostrat geologic column database and globally-distributed geological map units. Whether carbonate abundance is measured in absolute (area, volume) or in relative terms (carbonate normalized by total sediment), secular patterns emerge. In the Precambrian, carbonate abundance in continental crust is generally low. In the Phanerozoic, it climbs abruptly to a Paleozoic maximum and then declines towards the present. Decrease in shelf carbonate abundance across the Phanerozoic has been previously documented, driven in part by evolving paleogeography and the early Mesozoic evolution of pelagic calcifiers, which helped to shift carbonate burial from continental to oceanic crust. A Precambrian low in continental carbonate has received less attention. Here we propose that carbonate burial during much of the Precambrian was dominated by accumulation on (or within) oceanic crust and then shifted to continental crust in the early Paleozoic. Carbonate burial fluxes calibrated from the surviving rock record are an order of magnitude larger in the early Paleozoic than they appear to have been in the Proterozoic, with a step-wise increase occurring during the Ediacaran-Cambrian transition. This observation implies a large and relatively abrupt shift in the principal locus of CaCO 3 burial, from short-lived oceanic crust during much of the Proterozoic to longer-surviving continental crust in the early Paleozoic. Oceanic crust became, once again, a significant locus for carbonate accumulation during the Mesozoic and Cenozoic. The Paleozoic accommodation of most of the global carbon burial flux on the continents has many implications, including for secular changes in carbon cycling rates and the sensitivity of the surface environment to CO 2 injections.