DYNAMIC SEAFLOOR ENVIRONMENTAL CHANGES RECONSTRUCTED FROM FORAMINIFERAL ECOLOGY OFF THE PACIFIC COAST OF COAST RICA FROM IODP EXP 344

Dramatic tectonic activity off the Pacific coast of Costa Rica is likely to have caused significant changes in local seafloor conditions. These changes are reflected in benthic foraminiferal ecology observed in the >150µm fraction of Integrated Ocean Drilling Program Leg 344 U1413 core samples. Dominant infaunal taxa (living within sediments) of the assemblages examined include Uvigerina peregrina, Bolivina spp., Epistominella sp., and Angulogerina sp. While Cibicidoides wuellerstorfi and Planulina limbata were among the dominant epifaunal species (living on or above surface sediments). These dramatic shifts between prevalent infaunal and epifaunal species dominance likely reflects changes in past conditions, possibly through variations in quality and quantity of phytodetritus. The primary source of phytodetritus to the deep sea is from surface water productivity. The data set presented here builds on the foraminiferal ecologic investigation of core U1413 with an estimated time span of ~1,000-290,000ybp. The section of the core estimated to be in the range of 90,000-290,000ybp was examined in greater resolution as this portion of the core is thought contain paleo-ecological shifts suggestive of an increase in food availability estimated from 290,000 to 210,000 ybp, and a reduction in oxygen availability estimated at 290,000 and 205,000 ybp. Benthic foraminiferal assemblages at this location are consistent with species that are associated with conditions resulting from surface water productivity and oxygen availability. These environmental shifts may have been caused by regional tectonic activity. Fossil foraminifera and modern analogs have a special role in the reconstruction of paleoenvironmental reconstructions. The goal of this projects it to generate a thorough microfossil based paleo-reconstruction and proceed with geochemical and morphological analysis to verify our findings.