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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. [ABSTRACT FROM AUTHOR]

Although interactions between eolian and fluvial systems are well documented in both modern and ancient environments, there are few studies of such deposits that also address the paleosols that developed within them. The Cenomanian Candeleros and Huincul formations of the Neuquén Basin, Northern Patagonia, Argentina, provides an excellent opportunity to do so. These formations preserve mixed fluvial-eolian and fluvial systems, respectively, with associated pedogenesis. We identify five lithofacies associations (fluvial channel deposits [FA1], deposits of unconfined fluvial flows [FA2], floodplain deposits [FA3], eolian-dune deposits [FA4], and wet interdune deposits [FA5]), and five pedotypes (calcic Protosols [P1], Vertisols [P2], vertic and gleyed Protosols [P3a and P3b, respectively], vertic Calcisols [P4], and argillic Protosols [P5]). The lower Candeleros Formation is characterized by eolian dune deposits with calcic Protosols and wet interdune deposits with Vertisols and vertic and gleyed Protosols. The middle part of the formation is dominated by deposits of unconfined fluvial flows with vertic Protosols and, in the upper part of the unit, there are channel deposits with vertic Calcisols. The Huincul Formation is characterized by fluvial deposits with argillic Protosols. Changes in paleosol development have been recorded throughout the two formations. Small-scale changes, recognized in the lower Candeleros Formation, comprise a chrono-toposequence, in which calcic Protosols, Vertisols, vertic and gleyed Protosols are genetically associated with FA4 and FA5. Calcic Protosols developed on the dunes and gleyed Protosols in the inner part of the interdunes subjected to temporal waterlogging. When the dunes were vegetated and pedogenesis promoted dune fixation, the rate of dune mobility was slow and the ancient soils developed into Vertisols. In turn, the absence of vegetation was linked to a relatively high rate of dune migration, the time of soil development was limited, and, as a result, vertic Protosols were preserved. The analysis of soil-forming factors as large-scale controlling factors showed that throughout the succession, variations on the type of paleosol and the sedimentary environment over time were controlled by changes in ancient climate. Mid-Cretaceous global climate reconstructions suggest that the paleosols developed in northern Patagonia were located near the limit between the Southern Mid-latitude Warm Humid Belt and the Southern Hot Arid Belt. Seasonally arid and semi-arid conditions prevailed in this area, although there was a temporal trend towards a temperate subhumid climate. [Display omitted] • Cenomanian paleosols of the Candeleros and Huincul formations, northern Patagonia. • Paleosols spatial distribution shows small- and large-scale variability. • Climate controls paleosol types and sedimentary sub-environments. • Arid and semi-arid conditions prevaild with a trend towards a subhumid climate. [ABSTRACT FROM AUTHOR]

The Paleogene infill of the eastern Golfo San Jorge Basin, Patagonia, Argentina, is composed of marine (Salamanca Formation) and terrestrial (Grupo Río Chico and lower Sarmiento Formation) deposits. The Río Chico Group is a fluvial, pedogenically modified succession interlayered with eolian volcaniclastic deposits during the Eocene. Several authors have highlighted the stratigraphic significance and usefulness of strongly developed paleosols in the definition of sequence stratigraphic studies. Even though the area hosts abundant geological and paleopedological data, no large-scale (i.e., basin-scale) stratigraphic architectural correlation including paleosols and relationships within the sequence stratigraphic context had hitherto been carried out. By integrating previously published and unpublished data sets, this paper proposes a sequence stratigraphic framework for the middle Danian–middle Eocene successions of the eastern Golfo San Jorge Basin. Here, spatio-temporal changes in fluvial/alluvial architecture of the Paleogene infill allow us to define four depositional sequences (S), limited by sequence boundaries (SB) that internally presents a low-accommodation system tract (LAST), and a high-accommodation system tract (HAST). Part of these sequences occur as fining-upwards fluvial successions that are pedogenically modified on top by strongly developed paleosols, or are erosively overlain by the coarse-grained base of the following sequence without the development of well-developed paleosols. The sedimentological and paleopedological analysis of the four sequences identified for the early Paleogene infill of the basin indicates that the interplay between subsidence, base level, and climate controlled both fluvial style and landscape evolution, as well as soil development. Volcaniclastic supply also played a significant role, especially during the Eocene. Image 1 • Paleogene infill of the GSJB can be divided into 4 sequences. • Sequence boundaries are related to fluvial incision or to mature paleosols. • Mature paleosols reflect the transition from greenhouse to icehouse world. • Accommodation space, base level and climate controlled system tracts evolution. • Subsidence rates controlled fluvial architecture spatial variability. [ABSTRACT FROM AUTHOR]