Oceanography of the Gulf of Tehuantepec, Mexico, indicated by Radiolaria remains

The morphology of the Gulf of Tehuantepec, Mexico, is redefined through a bathymetric analysis and this redifinition is considered to explain the distribution patterns of non-carbonate sediments, particularly the radiolarian remains. Although the distribution patterns of pelagic sediments are influenced by the Gulf of Tehuantepec bathymetrical morphology and the terrigenous input, these “reflect” clearly the regional oceanography. Northern strong winds, called the “Tehuanos”, blowing across the sea surface of this Gulf when the Intertropical Convergence is at its southernmost position, define the main sedimentologic dynamics of this region. This wind field gives rise to an oceanic front at the southwestern part of the Gulf, as well as upwelling processes at its central-eastern part. In the mixing at the front there is some contribution of California Current waters, while in the upwelling area there is a large contribution of the tropical-subtropical water which is carried by the Costa Rica Coastal Current. This oceanographic framework controlls the makeup of radiolarian assemblages. Consequently, at the seabottom, under the oceanic front, the presence of the radiolarian species Lithomelissa thoracites and Cycladophora davisiana is observed, while under the upwelling region, Acrosphaera murrayana is conspicuous.