Paleolandscape reconstruction and interplay of controlling factors of an Eocene pedogenically-modified distal volcaniclastic succession in Patagonia

Abstract

The middle Eocene Koluel-Kaike Formation, located in the San Jorge Basin, Patagonia, Argentina, is a strongly pedogenically modified succession associated with volcaniclastic input in an aggrading distal eolian-dominated fluvial system, located ∼400 km downwind of the Eocene Andean volcanic arc. The coordinated study of sediments and paleosols of this unit allows (1) reconstruction of environmental conditions and landscape evolution, and (2) determination of the interplay of the main forcing factors in the evolution of the Kokuel-Kaike Formation. The landscape reconstruction attests to the existence of a loessic rolling plain drained by a subordinate fluvial system, composed of both unconfined and confined flows, with locally ponded areas. Over these, thick stacked cumulative paleo-Ultisols and vertic paleo-Ultisols developed with scarce simple and stacked compound vitric Entisols analogues and compound Inceptisols equivalents. This high-resolution sedimentological-pedological analysis of the Kokuel-Kaike Formation indicates that the interplay between episodic volcaniclastic supply and cyclic climate controlled landscape evolution and soil development.