Calcium Carbonate Sedimentation in the Global Ocean: Linkages Between the Neritic and Pelagic Environments

Abstract

(CaCO3) is the greatest source of sediment in the present-day ocean. Interest in carbonate sedimen-tation extends beyond geologists because the car-bonate system involves biologic and geochemical processes. Carbonate production, for example, re-leases CO2 but its accumulation becomes a major sink for inorganic carbon. Unlike fluvial sediments, modern carbonates accumulate more or less equally in the neritic and pelagic environments. Neritic carbonates (benthic) are characterized by rapid production of (mostly) metastable aragonite and magnesian calcite: pelagic production of (primarily) calcite in the open ocean occurs at much slower rates but over much larger areas than does neritic production (Table 1). A global understanding of the produc-tion, preservation, and accumulation of calcium carbonate thus necessitates understanding both the neritic and pelagic systems, even though commu-nication between researchers in the two subdisci-plines often has been minimal. In an effort to promote closer communication be-tween neritic and pelagic researchers, an NSF-funded workshop was held in Upper Brandon, Vir-ginia last autumn (13-16 October 1994), which brought together carbonate sedimentologists, mi-cropaleontologists, geochemists, and modelers. Workshop themes emphasized the role and relative importance of calcium carbonate in neritic and pelagic environments, linkages between the two in determining a global carbonate budget, and future research directions that might reduce uncertainties in our understanding of the global carbonate system. Although we delved into many topics in which our knowledge ranged from adequate to poor, three topics seemed to attract the most interest: how well we can quantify the global carbonate budget, whether the oceans are in steady state, and