Parasecuencias Transgresivo-Regresivas en un Cortejo Transgresivo: parte superior de la Fm utrillas en Olleros de Pisuerga, Palencia

Field and borehole data demostrate that the well-known fluviatile Utrillas Fm of N Spain is part of the transgressive system tract of a major second-order sequence. However, the analysis of its upper part in the Olleros de Pisuerga area (Palencia) and in the Trashaedo-1 borehole reveals the existence of three parasequences indicative of smaller scale transgressive-regressive episodes superimposed on the overall transgressive trend. These transgressive-regressive episodes have resulted in the vertical alternation of two different facies associations, a coarse-grained fluviatile association and a finer-grained littoral association, a favourable situation for the development of stratigraphic or mixed hydrocarbon traps that may prove of interest in future subsurface explorations.