Cretaceous-Cenozoic growth of the Patagonian broken foreland basin, Argentina: Chronostratigraphic framework and provenance variations during transitions in Andean subduction dynamics

Abstract

The Cretaceous-Cenozoic evolution of the Patagonian broken foreland basin system at 42-43°S in the northern Chubut province of Argentina is associated with variable retroarc phases of fold-thrust belt shortening, extension, and basement uplift during changes in the dynamics of oceanic slab subduction. Basement inheritance and progressive shallowing of an east-dipping subducting slab are important mechanisms of foreland partitioning, as dictated by the preexisting (pre-Andean) structural architecture and forelandward (eastward) advance of Late Cretaceous arc magmatism. Previously recognized growth strata help define the timing of fold-thrust belt shortening and retroarc basement-involved uplift, but the precise consequences for sediment routing remain poorly understood, with uncertainties in patterns of basin evolution before, during, and after shallowing and resteepening of the subducting slab. In this study, distinctive sediment source regions and magmatic histories enable evaluation of the stratigraphic and tectonic evolution of the retroarc foreland basin using new provenance results, maximum depositional ages, and isotopic signatures from detrital zircon U-Pb geochronology and Lu-Hf geochemical analyses. A compilation of published bedrock crystallization ages and distributions of metamorphic and igneous basement rocks identify: a western source region defined by the Andean magmatic arc and associated pre-Andean basement; and an eastern source region consisting of intraplate magmatic units and the North Patagonian Massif. We demonstrate that Aptian-Cenomanian retroarc basin fill was derived principally from the basement massif and intraplate volcanic units to the east, followed by a Late Cretaceous

The Influence of Climate on the Dynamics of Mountain Building Within the Northern Patagonian Andes

“…have also been reported for the Esquel Range, located in the frontal segment of the fold-thrust belt (Site 5). These indicate MDAs of 13.1 ± 0.2 Ma (17ESQ02) and 12.5 ± 0.3 Ma (17ESQ03) for the pre and syn-growth strata respectively (Butler et al, 2019). Farther east, Bucher et al (2019) described growth strata in the La Pava and Collón Cura formations in the footwall of the southwest-verging Taquetren thrust (Site 6), from which they obtained MDAs of 14.45 ± 0.13 Ma (PBG) and 11.6 ± 0.4 Ma (PLG).…”

“…This broad and discontinuous region is characterized by a series of uplifted basement blocks that grew separately from the main Andean axis and constitute the highest summits of the extra‐Andean region. The PBF hosts a series of synorogenic sedimentary basins filled with volcaniclastic, and continental deposits, including documented growth strata along associated thrust faults (Figure 3) (Butler et al., 2019; Echaurren et al., 2016; Garcia Morabito & Ramos, 2012; García Morabito et al., 2011; M. E. Ramos et al., 2015). Sediments within these basins provide a record of the regional geometry and kinematic history of the North Patagonian Andes since the Miocene.…”

“…Furthermore, basaltic lava flows and fluvioglacial deposits covering the synorogenic successions are locally tilted, and provide insight into the manner in which deformation has migrated in space and time. Low‐temperature apatite fission‐track and (U–Th)/He thermochronometry constrains the exhumation pattern in the orogen (Adriasola et al., 2006; Glodny et al., 2007; Thomson, 2002; Thomson et al., 2010), and the syn‐orogenic foreland deposits have been the focus of several works in recent years (Bucher et al., 2019; Butler et al., 2019; Echaurren et al., 2016; García Morabito et al., 2011; D. Orts et al., 2012; M. E. Ramos et al., 2015). The combination of these distinct data sets could provide a good general view on how the Patagonian orogen has evolved kinematically in time.…”

“…Growth stratal packages in the upper levels of the Ñirihuau Formation have also been described in the Esquel Range of the North Patagonian foothills (Figure 2. Site 5) (Butler et al., 2019). Here, progressive unconformities have been found in association with a basement cored anticline (Echaurren et al., 2016).…”

Cretaceous–Paleogene plant extinction and recovery in Patagonia

“…The San Ramón Section (SRS; Fig. 1B,D) studied here is the most complete of the Lefipán Formation (Scasso et al 2012), comprising marginal, tidal-flat deposits to fully marine sediments within a tidally dominated deltaic setting that ranges from ?Campanian-Maastrichtian to Danian in age (Legarreta and Uliana 1994;Spalletti 1996;Barreda et al 2012;Scasso et al 2012;Vellekoop et al 2017;Butler et al 2019). The K/Pg impact layer recognized at other sites around the world (e.g., Alvarez et al 1980Alvarez et al , 1990Orth et al 1981;Brooks et al 1986;Lerbekmo and St. Louis 1986;Schulte et al 2010) is not preserved in the SRS, probably due to bioturbation or erosion at that particular level (Scasso et al 2012).…”