Palaeogeography, Palaeoclimatology, Palaeoecology 577 (2021) 110553 Available online 2 July 2021 0031-0182/© 2021 Elsevier B.V. All rights reserved. Implications of palaeosols in low net-to-gross fuvial architecture reconstruction: Reservoir analogues from Patagonia and Spain Augusto Nicol´ as Varela a, b, * , Luis Miguel Yeste c , C´ esar Viseras c , Fernando García-García c , Dami´ an Moyano Paz d, e a C´ atedra de Micromorfología de Suelos, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Calle 122 y 60 s/n (1900), La Plata, Argentina b CONICET, Y-TEC (YPF-Tecnología), Av. Del Petr´ oleo s/n (1923), Berisso, Argentina c Sedimentary Reservoirs Workgroup (SEDREGROUP), Dept. of Stratigraphy and Palaeontology, University of Granada, Spain d C´ atedra de Sedimentología, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Calle 122 y 60 s/n (1900), La Plata, Argentina e CONICET, UNLP Centro de Investigaciones Geol´ ogicas, Diagonal 113 275, B1904DPK La Plata, Argentina A R T I C L E INFO Editor: Giorgio Basilici Keywords: Catenas Palaeotopographic relief Avulsion processes Outcrop analogues Cretaceous Triassic ABSTRACT The changes in the geometry, density and distribution of the fuvial reservoir sand-bodies have been modelled both in the laboratory and from outcrop analogues. On the other hand, fne-grained foodplain deposits, often called “background” sedimentation, have not been in the spotlight. However, they provide a very important database for fuvial architecture reconstruction and therefore constitute a key tool in characterizing, correlating and modelling heterogeneous fuvial reservoirs. The methodology used in this work combines classical sedi- mentological and palaeopedological data. Palaeosols were identifed in outcrops of the Cretaceous of Patagonia and Triassic red beds of Spain based on the main pedofeatures such as colour, soil structures, mottles, nodules, clay illuviation cutans, slickensides and rhizoliths. Palaeosol horizons, thickness and types of contact were described. The palaeosols classifcation was made through the comparison with the Soil Taxonomy. For the characterization of lateral palaeosols variability, several palaeopedological logs were constructed following the same stratigraphic level at both margins of the main channels. Small-scale or high-frequency palaeosol varia- tions, identifed in both fuvial succession are represented by the lateral and vertical superimposition of Incep- tisols/Entisols, Vertisols and hydromorphic Vertisols/swamp deposits. We recognized a decrease in the drainage conditions within the palaeosols catena moving away from the main channel bodies. The most waterlogged palaeosol is located at 200 to 300 m from the main channels. Lateral changes of palaeosols are interpreted as the result of intrinsic factors to the depositional systems, such as the relative position within the foodplain and the distance from the main channels, that condition the particle size of parent material, the sedimentation rate and the palaeotopographic position which state the drainage conditions of palaeosols. Vertical stacking of different palaeosols is linked to avulsion processes and the relatively abrupt change in the distance to main channels as the system aggraded. The study of these two environmentally similar examples (low-gradient meandering fuvial systems subjected to a high rate of aggradation), although located in different tectonic and chronostratigraphic contexts, shows that the type of fuvial system acted as the main control of sedimentary and pedogenic processes; as well as the scale at which they occur. Thus, when choosing an outcrop fuvial reservoir analogue, the type of fuvial system and climate should be more important than the age or the tectonic framework of the succession to be studied. 1. Introduction The characterization and understanding of fuvial sedimentary systems are important since they constitute important heterogeneous reservoirs of hydrocarbons and aquifers in many regions of the world. In this way there are abundant sedimentological studies focused on trying * Corresponding author at: C´ atedra de Micromorfología de Suelos, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Calle 122 y 60 s/n (1900), La Plata, Argentina. E-mail addresses: augustovarela@cig.museo.unlp.edu.ar (A.N. Varela), lmyeste@sedregroup.com (L.M. Yeste), viseras@ugr.es (C. Viseras), fgarciag@ugr.es (F. García-García), dmoyanopaz@cig.museo.unlp.edu.ar (D.M. Paz). Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo https://doi.org/10.1016/j.palaeo.2021.110553 Received 22 October 2020; Received in revised form 28 May 2021; Accepted 15 June 2021