Caracterización sedimentológica de un Sistema Fluvial Distributivo de clima árido: arroyo Papagayos, en el piedemonte oriental de las Sierras La Huerta-Imanas, San Juan, Argentina

Abstract

Recent studies proposed that distributive fluvial systems (DFS) occupy a great proportion in modern continental sedimentary basins, challenging classical sedimentary models proposed for similar ancient basin. Because of this, arises the importance of studying modern DFS with the aim of obtaining facial models to apply them in ancient deposits. In this paper, we analyze and discuss the sedimentary environments included in the modern deposits of the Arroyo Papagayos, Western Pampean Ranges, San Juan province, interpreted as a Distributive Fluvial System (DFS). We perform the study of the Papagayos creek by describing different architectural elements, which characterize the sub-environments organized in four zones from the mountain front to the distal playa lake. A low sinuosity gravelly-sandy bed braided fluvial system, characterizes the proximal zone. A medial to high sinuosity sandy-gravelly anastomosed-anabranching fluvial system describes the medial zone, where floodplain aggradation is domain by crevasse splays accretion. At this point, 10 km far from the mountain front, the deposits starts to develop a cone shaped morphology. A higher sinuosity flashy ephemeral meandering sandy-muddy fluvial system with eolian interaction defines the distal zone, where the main channel of the system disappears by low gradient of the topography and infiltration depositing muddy terminal splays. Finally, eolian dune and wet interdune deposits characterizes the fourth zone, interpreted as a transitional area between the DFS and the saline playa lake. A particular feature observed along the DFS system is that mudflows are the main sedimentary process in the floodplain, probably as the result of the combination of the seasonal arid climate and the Arroyo Papagayos drainage basin morphometry and the low gradient of the topography. The sedimentary process and environments recognized along the Arroyo Papagayos will allow a better understanding of arid DFS depositional dynamics as well as, to identify them in the geological record. Lastly, high aggrading conditions for DFS development will response to climate interaction between upland catchment area (semiarid) and valley (arid), drainage basin morphometry, smooth piedmont gradient and high tectonic subsidence of the basin, located in the Andean broken foreland.

Fluvial deposits of the Diamante Formation as a record of the Late Cretaceous tectonic activity in the Southern Central Andes, Mendoza, Argentina

“…On the other hand, the features of the described facies, their lateral and vertical relationship and the sedimentary processes reflected in these deposits partly coincide with the medial zone of fluvial fan or Distributary Fluvial System (DFS) models. Those facies models were described by several authors over the past few years (Nichols and Fisher, 2007;North and Warwick, 2007;Cain and Mountney, 2009;Hartley et al, 2010;Weissmann et al, 2010;Moscariello, 2017;Santi Malnis et al, 2018). More stratigraphic sections are needed to link the facies described in Vega Grande with a depositional environment of fluvial fan system or DFS.…”