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Paleofertility estimates are derived from organic-carbon accumulation rates determined in nonbioturbated mid-Cretaceous deep-sea deposits using organic-carbon preservation factors observed in laminated sediments from anoxic Holocene environments. The estimated mid-Cretaceous primary production rates are as much as an order of magnitude lower than those measured in today's oceans. An evaluation of dissolved oxygen budgets using a simple oceanic circulation model indicates very low deep-water renewal rates in mid-Cretaceous oceans.