Detailed stratigraphycal analysis based on six stratigraphycal columns in the type section of Formacion Zorritas, at Sierra Almeida, High Cordillera of Antofagasta, allows its division into three members. By means of detailed facial analysis of each of these members, environ mental conditions were reconstructed. The Lower Member is formed by coarse grained quartz arenites in which planar cross bedding and herring-bone cross bedding are common. They are interpreted as tidal deposits in a shallow marine environment. Presence of Tropidoleptus sp. and Australocoelia allows to date this member as Middle Devonian (Emsian-Givetian) even Frasnian. The Middle Member is composed by shales and very fine grained sandstones, with ripple marks and hummocky cross bedding. It represents sedimentation controlled by storms and waves in a nearshore environment. In its lower section, it contains Wocklumeria, an Upper Devonian form of goniatite. In its middle to upper section a faunal association diagnostic of Lower Carboniferous age was found. The Upper Member (Lower Carboniferous) is composed by fine-grained sandstones with planar cross bedding. Small erosional canals can be also observed. This member is interpreted as formed in a near shore fluvial environment. It has a regressive character. Considering the whole section of Zorritas Formation (3,040 m thickness) a complete transgressive-regressive cycle is apparent. No stratigraphycal discontinuity, nor discordance, was observed in the Devonian-Carboniferous boundary. Thus, in the precordillera of Region de Antofagasta there is no evidence of 'Chanic' Orogeny. The deposition of Zorritas Formation took place in a stable siliciclastic platform basin that in its eastern side was bounded by the 'Arco Puneno'. This was a positive relief that supplied from the southeast most of the detrital material to the basin. Detrital analysis of sandstone from Zorritas Formation suggests that the 'Arco Puneno' was formed mainly by metasedimentary elastic sequences associated with minor metamorphic rocks, plutonites and acidic to intermediate volcanic rocks. Detailed measurements of sedimentary structures made in all three members of Zorritas Formation, allow to stablish a northwestern direction for detrital supplies, coming from the 'Arco Puneno'. Lithological and facial correlations of Zorritas Formation with other outcrops of the same age along the Argentinian-Chilean border are suggested. Paleogeographical and geotectonic comments about this realm during Devonian-Lower Carboniferous time are also suggested.