Source-to-sink analysis of continental rift sedimentation: Triassic Cuyo basin, Precordillera Argentina

Abstract

The northernmost outcrops of the Triassic extensional Cuyo basin in western Argentina reveal a basal coarse conglomerate overlain by a thinning-fining upward siliciclastic red-bedded section with subordinated tuffs and microbial-rich carbonates (Cerro Puntudo Formation), unconformably covered by a second coarse conglomerate (El Relincho Formation), which were previously interpreted as two rifting events. An integrated analysis of facies associations, stacking patterns, paleocurrent and provenance was carried out in order to reveal the rift sedimentation using a source-to-sink approach. Besides the traditional controls in continental basins (e.g., sedimentation, tectonics and climate), this study considers possible drainage pattern evolution in order to differentiate isolated versus integrated depocenter stages. U-Pb zircon data corroborate our analysis and reveal a volcanic basement source of 256.8 ± 3.5 Ma (Permian/Lopingian) and a sedimentation age of 249.8 ± 2.5 Ma (Early Triassic) for a tuff interbedded within the Cerro Puntudo Formation, complementing previous age of 243.8 ± 1.9 Ma (Middle Triassic) at the top of this unit. Stratigraphic stacking allows the interpretation of three evolutionary stages. A first stage, represented by thick massive boulder-volcanic-rich conglomerates characterizing alluvial fan deposition, indicates strong tectonic activity of border faults (first rifting event). These features suggest high surface gradient and high available space controlling accommodation and dispersal of gravity and debris-flow deposits. Paleocurrents to the east reveal largely north-south normal faults located to the west and sediment supply from a proximal volcanic source area. A second stage, represented by a notable fining-thinning upward facies, including fluvial and palustrine (stromatolites with pedogenetic features) deposits, indicates a transition to tectonic quiescence. These facies associations developed in a context of low sedimentation rate, limited tectonic relief and low accommodation space. A third stage is represented by greenish well-rounded coarse-grained polymictic conglomerates of El Relincho Formation that unconformably truncate the Cerro Puntudo Formation. These conglomerates are interpreted as perennial braided fluvial systems (with paleocurrents to the northwest) indicating drainage reorganization primarily influenced by climate change and combined tectonic reactivation, previously considered the second rifting event. Climate change affected sediment delivery and allowed regionally connectivity and overfilling of the depocenters. In this last stage, northwest axial transport from variable sources within the Precordillera (to the southeast) is inferred from provenance analysis indicating open linkeddepocenters. This study suggests a new stratigraphic correlation for the northern part of the Cuyo basin, implying that during the first rifting event a semi-arid climate prevailed with development of isolated and independent depocenters (first and second stages), whereas above the unconform...

The stem-archosaur evolutionary radiation in South America

“…Radioisotopic dates have constrained the age of the Cerro Puntudo Formation between 249.8 ± 2.5 Ma and 243.8 ± 1.9 Ma (Mancuso et al, 2010;Teixeira et al, 2018), thus indicating a deposition time that took 1.6-10.4 My taking into account dating errors, spanning the latest Permian− earliest Ladinian as maximum and the latest Olenekian− middle Anisian as minimum ages (Fig. 2).…”

Modern Dryland Source-to-Sink System Segments and Coupling Relationships from Digital Elevation Model Analysis: A Case Study from the Mongolian Altai

“…Sediment distribution in a source-to-sink (S2S) system corresponds to linked segments of sediment routing pathways from areas of erosion in the hinterland to areas of deposition in the basin, often embracing the dynamic processes and feedback mechanisms between the autogenic and allogenic forcing conditions that govern sediment dispersal in erosional-depositional systems [1][2][3]5,8,24]. Source-to-sink analysis in a dryland uplift system, however, needs to be implemented, including the characteristics of bedrock and catchment units, sediment transport pathway types and sizes, sedimentary architecture and fluxes, and the proportional range between source-to-sink segments [4,5,9,[36][37][38][39][40].…”

“…The source-to-sink (S2S) system (sediment routing system) is a complete analysis with sediment moved from the erosional engine of uplifts/mountains to its eventual site of deposition (Figure 1), and it has been a major area of research in recent years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. A principal aim of S2S system research is to better understand the dynamic surface processes and landscape evolution of sediment production, transport, and deposition [21,22] in different regions, including continental marginal basins [4][5][6]23], lacustrine basins [10,[24][25][26], and glacial erosion or production [27][28][29][30][31][32].…”

The paleoclimatic context for South American Triassic vertebrate evolution

“…The playa lake has been classified as a balanced-fill through flow lake (Benavente et al, 2019). The unit has been U-Pb zircon dated in the lower half section 249.1 ± 9.1 Ma (LA-ICP-MS, Teixeira et al, 2018) and near its top as 243.4 ± 4.0 Ma (SIMS, Mancuso et al, 2010) constraining its deposition to late Early-Middle Triassic (see Irmis et al, this volume for further discussion). The vertebrate assemblage in the Cerro Puntudo Formation is limited to a single pelvic girdle (Mancuso 2009) and footprints from early archosaurs (Benavente et al, 2015).…”