Dinoflagellate cysts were used as paleoenvironmental indicators to determine the presence of Mediterranean Outflow on the Iberian Abyssal Plain. Sediment cores from three sites, 897A, 899A, and 900A from ODP Leg 149, were used to produce the reconstruction. The sediment cores span from Pliocene to Late Pleistocene in age and are on a transect from the continental rise to the abyssal plain. The upper part of the sedimentary sequences of core 897A, and 900A revealed deposits of turbidity currents. The presence of turbidites explains high ratios as site 897A and low ratios at site 900A, with regards to relative abundance of dinoflagellates and pollen. It was also possible to determine when Mediterranean outflow appeared to have influence on the abyssal plain environment by using Polyspheridium zoharyi, Lingulodinium machaerophorum, Operculodinium israelianum, and Operculodinium crassum as markers of warm, saline Mediterranean water. A shift in water masses from transitional-subtropic to subpolar water was also observed at Site 900A. The data collected corresponded with data from another site on the Iberia Abyssal Plain, ODP Site 898 and sites off New Jersey, DSDP 604, 607, and 613, indicating a simultaneous shift in ocean circulation of the Atlantic at approximately 1.4 Ma. The change in water masses has been linked to the theory of the shrinking of the subtropical gyre.