Eastward Andean orogenic growth since the late Oligocene led to variable crustal loading, £exural subsidence and foreland basin sedimentation in the Chaco basin.To understand the interaction between Andean tectonics and contemporaneous foreland development, we analyse stratigraphic, sedimentologic and seismic data from the Subandean Belt and the Chaco Basin.The structural features provide a mechanism for transferring zones of deposition, subsidence and uplift.These can be reconstructed based on regional distribution of clastic sequences. Isopach maps, combined with sedimentary architecture analysis, establish systematic thickness variations, facies changes and depositional styles.The foreland basin consists of ¢ve stratigraphic successions controlled by Andean orogenic episodes and climate: (1) the foreland basin sequence commences between $27 and 14 Ma with the regionally unconformable, thin, easterly sourced £uvial Petaca strata. It represents a signi¢cant time interval of low sediment accumulation in a forebulge-backbulge depocentre. (2) The overlying $14^7 Ma-old Yecua Formation, deposited in marine, £uvial and lacustrine settings, represents increased subsidence rates from thrust-belt loading outpacing sedimentation rates. It marks the onset of active deformation and the under¢lled stage of the foreland basin in a distal foredeep. (3) The overlying $7^6 Ma-old, westerly sourced Tariquia Formation indicates a relatively high accommodation and sediment supply concomitant with the onset of deposition of Andeanderived sediment in the medial-foredeep depocentre on a distal £uvial megafan. Progradation of syntectonic, wedge-shaped, westerly sourced, thickening-and coarsening-upward clastics of the (4) $6^2.1 Ma-old Guandacay and (5) $2.1 Ma-to -Recent Emborozu¤ Formations represent the propagation of the deformation front in the present Subandean Zone, thereby indicating selective trapping of coarse sediments in the proximal foredeep and wedge-top depocentres, respectively.Overall, the late Cenozoic stratigraphic intervals record the easterly propagation of the deformation front and foreland depocentre in response to loading and £exure by the growing Intra-and Subandean fold-and-thrust belt.

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