Present and Holocene Sedimentary Record of the Gulf of Tehuantepec Upwelling System.

The distribution patterns of planktonic foraminifera in sediments and their relationship to ocean dynamics and upwelling were studied in the Gulf of Tehuantepec. The Gulf of Tehuantepec, in the Mexican Tropical Pacific, is influenced by northerly winds that produce intense upwelling during Winter and early Spring. These oceanographic conditions leave an imprint in the sedimentary record of planktonic foraminifera which can be used to reconstruct upwelling variations through time. Recent distribution of foraminiferal assemblages are closely related to oceanographic patterns produced by upwelling dynamics. The Globigerina bulloides assemblage dominates most of the gulf's area under the influence of upwelling, while the Globorotalia menardii-Pulleniatina obliqueloculata assemblage is present in the region of warmer and stratified waters. The Globigerinita glutinata assemblage reflects the axis of upwelling and the borders of the associated cyclonic gyre. Holocene records of these assemblages indicate variations in the oceanographic dynamics through time, with maximum upwelling conditions coincident with the early Holocene Thermal Maximum.