The Cadiz region lies between the Iberian borderland and Morocco, west of the Strait of Gibraltar and the Western Mediterranean. Core GeoB9064-1 (35°24,91’N 6°50,72’W) is located in the southwest at a depth of 702 m, close to the Al Arraich mud volcano field 30 km off the Moroccan margin„ and has a length of 544 cm. Like most coastal regions, the southern Cadiz region is characterised by a coccolith assemblage dominated by the placoliths Emiliania huxleyi and Gephyrocapsa muellerae.Late Quaternary fluctuations are pronounced in this core, as shown by geochemical (TOC and CaC03) and XRF analysis (K, Mg, Fe, etc.), but also in abundances of coccoliths and more particularly Emiliania huxleyi. These can be related to upwelling and/or bottom currents.Colmenero-Hidalgo (2002) has split up Emiliania huxleyi in a larger coldwater and smaller warmwater variety based on a 4 µm cut-off value. Colmenero-Hid algo (2004) identified a deglacial decrease in the larger coldwater variety.In this study, 100 Emiliania huxleyi and 100 Gephyrocapsa muellerae lengths were measured in 30 samples. Comparison of the biometry of Emiliania huxleyi and Gephyrocapsa muellerae shows that these both species have similar fluctuations and both become smaller during the Holocene, revealing the splitting of Emiliania huxleyi in two morphotypes, to be more complex. A new method to tackle this problem is proposed
