Late Quaternary water mass variability derived from the pteropod preservation state in sediments of the western South Atlantic Ocean and the Caribbean Sea.

Evaluation of production, accumulation, and dissolution of calcium carbonate (CaC03) is of major interest for paleoceanographers since the carbonate system is intimately related to atmospheric C02. Pteropods are marine gastropods, which have adapted themselves to pelagic lire and are widcly distributcd and abundant in all oceans. Shelled pteropods and heteropods are the principal pelagic producers of aragonite, a metastable polymorph or CaC03 that is more soluble in seawater than calcite. Aragonitic pteropod production is calculated to average about 10% (Fabry, 1990; Fabry and Deuser 1991, 1992) to 12% (Berner and Honjo, 1981) of the total carbonate production. However, pteropod oozes are predominantly found in shallow and intermediate water environments since aragonite dissolves at much shallower water depths than calcite. Alternating modes of preservation of pteropod shells are related to differences in the bottom-water saturation state with respect to aragonite. In the present study, variations in the preservation state of pteropod tests are used toreconstruct late Quaternary changes in intermediate and deep water circulation in the South Atlantic Ocean and in the Caribbean Sea.