Pleistocene-Holocene Changes in Sedimentation Patterns Associated to Upwelling in the Gulf of Tehuantepec

Present day biogenic and non-biogenic sedimentation in the Gulf of Tehuantepec (Mexican Tropical Pacific Ocean) is modulated by upwelling resulting from northerly winds acting perpendicular to the coast. We present here micropaleontological and magnetic mineralogy data of a sediment core collected in the upwelling- influenced region of the Gulf of Tehuantepec. Core MD02-2523 is 39.5m long and was collected as part of the IMAGES MONA cruise at a location 15°25.74N and 94°14.33W, corresponding to 220m water depth. Radiocarbon dating and oxygen isotope stratigraphy suggest the core reaches the marine isotope stage 5. Although carbonate dissolution is conspicuous at certain levels, the biogenic record of planktonic foraminifera show upwelling during the Holocene and the presence of a stratified water column during most of the Pleistocene. Low field magnetic susceptibility was measured through the core, showing higher values towards the top and cyclic changes with depth. Magnetic susceptibility shows several cyclic peaks along the core that indicates an increase in the amount of magnetic minerals. It seems that they could be associated to (about 20 ka) precession cycles. Magnetic susceptibility correlates with terrigenous input and is related with material transported by the strong northerly winds in the gulf and isthmus region.