LAUSR

Abstract The initial infill of the Patagonian Broken Foreland is related to Miocene, syn-orogenic, volcaniclastic successions accommodated in intermontane basins. In the last years several works have paid attention to these successions due to their role in the comprehension of the timing of deformation, the relationship between arc-volcanism and the environmental signals, and the climate changes related to the growth of the orogen. In this paper we perform the U-Pb geochronology and the sedimentologic and paleosols analyses of a Miocene, syn-orogenic, volcaniclastic succession (La Pava Formation) located at the northern part of Patagonian Broken Foreland. The results indicate that the syn-kinematic sedimentation (evidenced by growth strata and progressive unconformities) proceeded between ~19 Ma to ~14 Ma, associated with arc-derived volcaniclastic deposits, under alluvial conditions with profuse paleosols development. The facies analysis combined with the paleosols and provenance studies indicate episodic and cyclic supply of pyroclastic materials, which were mainly delivered from the catchment area of the system, affected by explosive volcanism. A succession of stacked paleosols was recorded into 3 sections, bounded by unconformities, which record from Alfisols-like, Vertisol-like to Andisols-like paleosols. Paleosols variations were related to the effects of tectonic events, climate changes or to the increase of volcanic supply in comparison to soil-forming processes. The results obtained in this work are considered substantial to unravel the tectonic, volcanic and paleoclimatic framework of the North Patagonian Andes.