Sedimentación lacustre glaci-dominada en la Formación Tarija (Carbonífero), Sierra de Aguaragüe, Noroeste Argentino

the tarija formation (macharetí group) is mainly composed by gray diamictites which have been deposited under the glacial sedimentation that took place during the upper carboniferous period in gondwanaland. this paper describes the facies and facies associations of itacuamí and tarija formations of five section located in the aguaragüe range, sub-andean belt of salta province, argentina (fig. 1). the tarija formation outcrops almost completely (620m thick) and consist of gray diamictites, interbedded with fine sandstone levels and laminated mudstones. the basal contact is transitional with the itacuamí formation and the upper contact is an erosive unconformity with las pe？as formation (mandiyutí group). the itacuamí-tarija cycle can be divided into three sections, according to the facies associations considered. the lowermost section is formed by the facies association i (fai of fig. 2), composed by laminated mudstones (fl and fm) and thin bedded sandstones (st and sm). towards the top of the basal section, 34 m of white coarse and thickening upward sandstones (st, sh, sr and fl) intercalate. these also show a gentle downstream accretion structure (figs. 2 and 3-a). the middle section is formed by the facies association ii (fig. 2), which is composed by different levels of stratified and massive sandy muddy diamictites (dms and dmm) and mudstones (fld). in these diamictite, it is quite common to find scattered faceted and striated clasts (fig. 3-f and 4-c). there are two kinds of interbedded sandstones, coarsening - upward succesions and fining upward ones, both showing deformed, folded and dewatering structures (figs. 3-d and 3-e). the fl facies, composed by shale and siltstones have plenty of outsized clasts, which have been interpreted as dropstones (facies fld). the upper section (fa iii, fig. 2) is made up of massive diamictites (dmm, figs. 4-c and d) and stratified ones with frequent traction current structures (sr). in this section, levels of lenticular sands