Estimates of long-term sedimentation rates derived from total sediment thickness and bedrock ages based on current tectonic models consistently yield cm/ka-scale average sedimentation rates in the central Arctic Ocean, including the Lomonosov Ridge. The physiographic setting of the Arctic Basin is that of a small basin surrounded by huge landmasses since its initial opening during Early Cretaceous times, a setting that has contributed to yield 2-6 km thick sediment deposits on Arctic's abyssal plains. This sedimentation rate scenario is contrasting to the long-held belief that central Arctic Plio-Pleistocene sedimentation rates have been on the mm/ka-scale, or even sub-mm/ka-scale, as estimated from numerous short gravity or piston cores. ACEX drilled through a nearly 410 m thick latest Paleocene to Recent sediment section on the Lomonosov Ridge near 88°N at about 1200 m water depth, with a recovery of 68 %. A combination of paleomagnetic, biostratigraphic and 10-Be data derived from the ACEX cores finally solved the Arctic Basin sedimentation rate ambiguity, in showing an average middle Miocene to Recent rate of about 1.3 cm/ka and Pleistocene rates of nearly 2 cm/ka. The ACEX record is interrupted by a hiatus encompassing the interval between about 17 Ma and 43 Ma. Average middle Eocene through latest Paleocene rates are on the order of about 1.5 cm/ka.