Systematic regional mapping in the area of Timbio (Plancha 364) revealed the presence of ultramafic lavas, associated with the melange zone of the Romeral Fault system, which separates oceanic and continental domains. The outcrops are located in a stream, quebrada La Playa, 6,5 km south-west of Timbio. The flows belong to a sheared, incomplete ophiolitic sequence, probably-lower Cretaceous in age, which contains tuffite, breccias, pillow lavas, ultramafic rocks, and marine sedimentary rocks. Also found in this area, a allochtonous blocks, are graphitic schists and quartzites. The ultramafic lavas are composed of serpentized olivine clinopyroxene, plagioclase, and chromite spinels and altered glass; the color index is 90. The rock has a porphyritic texture, with olivine phenocrysts, amygdules; and the microspinifex texture in the matrix. One amigdaloidal wehrlite is near to the lava and it is possible that both rocks belongs to the same ultramafic flow. This new finding confirms once more that this rare rock type can occur in post pre-Cambrian terranes and leads to new ideas on the Earth's thermal history.