Geochemical and mineralogical comparison of a sequence of "wet" and "dry" samples from the lzarra-1 drilling belonging to the Zufia formation (Estella, Navarra) has been made. The following techniques have been applied; X-rays, over total dust and gas crhomatography, over fraction obtained after a disolvent extraction of the organic matter. These techniques show a high relation between the two types of samples, changes either in mineralogical composition nor in organic composition not being seen. Futhermore, the anoxic character, the maturity degree and the continental origin of the organic matter is observed