Tectonic evolution of the northern Austral-Magallanes basin in the Southern Patagonian Andes from provenance analysis

Abstract

We studied the northern tip of the Austral-Magallanes basin in the Southern Patagonian Andes, between the Buenos Aires Lake and the Mayer River at 46º35' SL and 48º35' SL, respectively. Proposed objectives were: i′ to differentiate Mesozoic-Cenozoic tectonostratigraphic units and, ii′ to characterize the different deformational events that took place in the area linked to a variable regional geodynamic context. Sandstones provenance analysis was performed on the Aptian -Albian compressive retroarc deposits and Cenozoic foreland deposits. Studied samples were classified using tectonic discrimination diagrams which show: i′ for Cretaceous rocks a dominant sediment source from a recycled orogen and, to a lesser extent, a dissected to transitional arc whereas ii′ the Cenozoic rocks show a magmatic arc provenance. According to the performed analyses, the evolution of the northern sector of the Austral-Magallanes basin is proposed to include four tectonostratigraphic units related to: i′ a Late Jurassic rift stage; ii′ a Berriasian Barremian thermal subsidence stage; iii′ an Aptian Albian compressive retroarc stage; and iv′ a Miocene foreland stage s.s. The Late Cretaceous-Paleocene was

Tectonic Subsidence Modeling of Diachronous Transition From Backarc to Retroarc Basin Development and Uplift During Cordilleran Orogenesis, Patagonian‐Fuegian Andes

“…Tectonic subsidence during the Late Cretaceous was most pronounced in the central sector. We note that whereas accelerated subsidence is not observed in the subsidence results at Lago Posadas (Figures 5c–5f and 6a), sediment provenance data, stratigraphic analysis, and structural data sets from this area indicate an Aptian transition to a retroarc foreland basin setting at this time (Barberón et al., 2019; Ghiglione et al., 2015; Ronda et al., 2019).…”

“…Extension led to thinning of the continental lithosphere and mid‐ocean ridge magmatism that formed oceanic lithosphere in a northward “unzipping” of the RVB in the southwestern portion of the basin between ∼50 and 54°S (Dalziel et al., 1974; Stern & de Wit, 2003). Rift volcanism and fault‐controlled subsidence coincided with deposition of both continental and marine synrift volcaniclastic successions (El Quemado/Tobífera/LeMaire Formations), followed by postrift thermal subsidence/sag deep marine black shales and shelfal black shales with interbedded siltstones and sandstones (Zapata/Río Mayer Formations) in the northern and central sectors that grade to a volcaniclastic apron of deep‐marine andesite‐rich turbidites and mudstones (Yaghan Formation) in Tierra del Fuego (southern sector; Figure 2; Table 1 and Table S1; Barberón et al., 2019; Biddle et al., 1986; Fildani & Hessler, 2005; Ghiglione et al., 2015; Hanson & Wilson, 1991; Moraga, 1996; Natland et al., 1974; Olivero & Malumián, 2008; Richiano et al., 2012; Schwarz et al., 2009; Wilson, 1991).…”

“… Chronostratigraphy of the Rocas Verdes (RVB) and Magallanes‐Austral Basins (MAB) at the studied localities: (a) Lago Posadas after Barberón et al. (2019). (b) N. Lago Viedma after Sickmann et al.…”

Tectonic segmentation across Patagonia controlled by the subduction of oceanic fracture zones

“…In the vicinity of the CTJ shear wave splitting studies show ENE trends related to the upper mantle flow from west to east through the slab window (Russo et al, 2010). From this ongoing process, the upper plate crustal structure south of the CTJ registered the subduction of different segments of the former Chile Ridge at these latitudes (Lagabrielle et al, 2007;Scalabrino et al, 2009;Barberón et al, 2018Barberón et al, , 2019. The Andean front at the northern part of the Austral Basin (Fig.…”

“…The Andean front at the northern part of the Austral Basin (Fig. 12) have experienced differential growth of eastward advancing thrust systems in Miocene times controlled by enhanced plate coupling driven by the approaching ridge segments (Lagabrielle et al, 2007;Scalabrino et al, 2009;Barberón et al, 2018Barberón et al, , 2019. Following the Chile Ridge subduction and subsequent opening of the slab window, a extensional or transtensional tectonic event occurred after 5 Ma, reactivating ENE and NNW-trending lineaments (Lagabrielle et al, 2007;Scalabrino et al, 2009).…”