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Fotografías de las facies de la asociación de facies II. a) base del Miembro Bandurrias sobre la discontinuidad principal, que descansa sobre facies heterolíticas (Ht) del Miembro Quién Sabe. El banco sobresaliente inferior, de colores más claros, es una coquina con fósiles bien triturados (facies Bc) y por encima siguen facies Ap. Escala gráfica 1 m; b) mismo nivel que en 5a, pero con mayor desarrollo de estructuras, de mayor escala y espesor total del banco. En el centro de la fotografía se encuentra una persona (1,8 m); c) areniscas con estratificación entrecruzada de mediana escala (Ap) de base tangencial, con cortinas de fango, algunas periódicamente más gruesas , que sugieren la presencia de tidal bundles, cubiertas por areniscas con óndulas (Ao). Piqueta: 30 cm; d) superficie erosiva en la base de un cuerpo arenoso canalizado, con areniscas con estratificación entrecruzada (Ap), labrado sobre facies heterolíticas (Ht). Piqueta 30 cm; e) parte superior del afloramiento de la Estancia Quién Sabe en donde se destaca en colores claros el cuerpo de tobas, compuesto por facies Tv y Tf, de 11 metros de espesor máximo. Por debajo de éste hay facies finas (Ht). Se destacan una barra arenosa submareal (facies Ap) en la parte inferior de la fotografía y un banco fosilífero en el centro de la misma (facies Bc). Escala gráfica 3 m; f) vista de detalle de las estructuras de corriente (estratificación entrecruzada de pequeña escala; estructuras de corte y relleno) en la parte superior del cuerpo tobáceo. (I) intraclasto pelítico. Piqueta: 30 cm. Fotografías 5a, 5c, 5d, 5e y 5f en Estancia Quién sabe; fotografía 5b en La Sección Sur.
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Se estudia la sedimentología de detalle del Patagoniano y su transición a la Formación Santa Cruz, aflorantes al sur del lago Argentino, Patagonia Austral. Las rocas analizadas consisten de aproximadamente 180 metros de una sucesión de areniscas fosilíferas que fue dividida en doce litofacies, agrupadas en tres asociaciones de facies. De base a tec...
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... La Irene and Calafate formations are best represented near El Calafate village, reaching a total thickness of ~500 m, deposited on top of the La Anita Formation; since the Cerro Fortaleza Formation is absent there (Marenssi et al., 2002;Povilauskas et al., 2008;Casadío et al., 2009;Cuitiño and Scasso, 2010). At that location, the Calafate Formation was dated at 69 ± 3 Ma using U/Pb geochronology . ...
... The lower Miocene Río Leona Formation is covered with a widespread lower to late Miocene continous succession (Cuitiño et al. 2019a). These deposits starts with shallow marine beds from the Patagonian sea transgression under the name of Estancia 25 de Mayo Formation (Cuitiño and Scasso, 2010;Cuitiño et al., 2015;Parras and Cuitiño, 2018;Cuitiño et al. 2019a;Parras and Cuitiño, 2021). The Santa Cruz Formation and their equivalents transitionally overlie the marine transgression. ...
We present a multidisciplinary study in the Austral-Magallanes basin combining U-Pb geochronology and provenance analysis with structural modelling to unravel the evolution of the fold-thrust belt and related foreland basin sedimentation. Our approach is innovative for the studied area, where the foreland stratigraphic record comprises a stack of marine deposits exceeding 5000 m in thickness. Using zircon U-Pb geochronology from 13 samples distributed through the foreland deposits in the Southern Patagonian Andes at 51°20'S latitude, we calculated maximum depositional ages and analyzed regional variations in provenance. The older sample, with an age of 96.0 ± 1.5 Ma, corresponds to the first sandstone beds of the Punta Barrosa Formation, whereas the uppermost sample, with an age of 17.9 ± 0.4 Ma stems from the Santa Cruz Formation. Furthermore, the
presented data help to complete the geochronological information existing for the South Patagonian Andes, by informing the regional geodynamic framework and timing variations. Linking new and previously published data regarding detrital zircon provenance, maximum depositional ages analysis, thermochronology and stratigraphic data with a balanced structural cross section, we propose a step-by-step model combining the kinematic evolution of the fold-thrust belt orogenic front with the basin history. A wedge-top setting for the Late Cretaceous is recognized, as well as two minor uplift events by Eocene time, followed by a major Miocene tectonic exhumation event.
... This is related to the initial Miocene stages of the development of a fold and thrust belt, which would have produced subsidence along the foot of the Southern Patagonian Andes and a major increase in the accommodation space. In the study area, this stage is represented by the shallow-marine deposits of the El Chacay Formation and their equivalents in the north and south (Furque and Camacho 1972;Chiesa and Camacho 1995;Giacosa and Franchi 1997;Cuitiño and Scasso 2010;Parras et al. 2012;Cuitiño et al. 2015Cuitiño et al. , 2019cAramendía et al. 2019;Parras and Cuitiño 2021). Within the study area, a change in thickness of the shallow-marine deposits is observed from north to south, from 130 m in the WLBAP section, to 145 m in the LP section, and 165 m in the LO area ( Fig. 3 and Table 1). ...
Detrital zircon U–Pb geochronology is a widely used technique for interpreting sedimentary provenance in basin systems. This, combined with detailed sedimentary facies interpretation and stratigraphy evolution, has been extensively applied in foreland basin settings to understand tectonic processes by tracking the exposure and erosion of distinct sediment source areas through time. We present a case study in the Miocene foreland sedimentary record of the NW Austral–Magallanes Basin ( c. 47° 30′ S), which is associated with the main phase of Andean uplift. We define three sedimentary units (SU) for palaeoenvironmental interpretation from shallow-marine deposits (SU-I) to mixed-load fluvial deposits (SU-II) to an alluvial fan (SU-III). Also, we constrain the timing of this synorogenic clastic wedge between c. 20 and c. 12 Ma applying U–Pb zircon maximum depositional ages of six sandstones and one tuff sample. From detrital zircon provenance analysis, we document a progressive upsection loss of contribution from younger units and an enrichment of older units derived from hinterland sources, suggesting the development of an unroofing erosional process owing to coeval Andean uplift of the cordilleran sources. Tectonostratigraphic stages determine the initial stages of orogenic uplift (Stage 1), the subsequent advance of the orogenic belt and progressive loss of accommodation space (Stage 2) and finally foreland clogging (Stage 3).
Supplementary material: Geochronological U–Pb isotopic ratios are available at https://doi.org/10.6084/m9.figshare.c.6132000
... The lower Miocene Río Leona Formation is covered with a widespread lower to late Miocene continous succession (Cuitiño et al. 2019a). These deposits starts with shallow marine beds from the Patagonian sea transgression under the name of Estancia 25 de Mayo Formation (Cuitiño and Scasso, 2010;Cuitiño et al., 2015;Parras and Cuitiño, 2018;Cuitiño et al. 2019a;Parras and Cuitiño, 2021). The Santa Cruz Formation and their equivalents transitionally overlie the marine transgression. ...
... Raggio et al. Cretaceous Research 128 (2021) 104968 Aydin, 2008; Cuitiño and Scasso, 2010;Fosdick et al., 2011;Bernhardt et al., 2011;Ghiglione et al., 2014). The Upper Jurassic continental volcaniclastic synrift (Calder on et al., 2007;Malkowski et al., 2016), is covered by Lower Cretaceous continental to marine sag sequences of the Springhill and Río Mayer/ Zapata Formations (Richiano et al., 2015;Zerfass et al., 2017). ...
... Detrital zircon samples from the Río de las Chinas (Fig. 2) in the Man Aike Formation, yield middle Eocene MDAs with a prominent 45e40 Ma age cluster (George et al., 2020). The Rio Leona, Centinela and Estancia 25 de Mayo Formations, which are not depicted in this study, complete the Cenozoic sequence (Marenssi et al., 2002;Casadio et al., 2009;Cuitiño and Scasso, 2010). ...
... Collected samples and geochronological results are indicated. Cerro Fortaleza profile is simplified afterAmbrosio (2008) andReinoso (2010), and Cerro Cafalate profile compiled and simplified afterMarenssi et al. (2002);Casadio et al. (2009), Povilauskas et al. (2008;Cuitiño and Scasso (2010). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.) ...
A key event in the paleogeographic evolution of the Austral-Magallanes foreland basin was the Santonian-Maastrichtian continentalization, marked by the appearence of deltaic, fluvial and wetland sequences stacked on top of deep marine deposits. The expanding ecological niche was exploited by theropods and influenced the evolutionary history of dinosaurs. We present new detrital zircon U-Pb geochronological data across this littoral to continetnal depocenter, in order to provide insights of its age, geographical extension, source regions and geodynamic setting. Littoral sandstones from La Anita Formation yield Maximum Depositional Ages (MDA) between ~86-80 Ma (weighted mean ages), and ~79-78 Ma youngest zircons. Our results are in accordance with Santonian-Campanian depositional age. The sequence continues with badlands and fluvial systems (Cerro Fortaleza and La Irene Formations), followed by meandering fluvial and lacustrine deposits (Chorrillo Formation). Transgressive marine facies topping the sequence (Calafate Formation) yield a preferred Maastrichtian 69 ± 2 Ma MDA from the youngest zirzon. The provenance and tectonic analyses indicate that basin shallowing during Santonian-Campanian times was driven by advance of the orogenic front, which produced the shift from foredeep setting to a wedge-top depozone. The unroofing of progressively deeper structural levels is registered in the basin fill, which suggests exhumation in the Basement domain during the Santonian-Maastrichtian.
... Thus, the return to the Miocene deposition may have been triggered by the creation of new accommodation space promoted by faulting. This process was combined with the overall Miocene global sea-level rise, an event also recorded in many other areas of South America (Mörner, 1991(Mörner, , 2009Frassineti and Covacevich, 1999;Scasso and Castro, 1999;Cuitiño and Scasso, 2010;Cuitiño et al., 2012) and also worldwide (e.g., Haq et al., 1987;Miller et al., 2005). ...
The post-rift tectono-sedimentary history of passive margins has been an issue of increased interest after the perception of their unsteady nature during the Neogene and Quaternary. The evolution of the eastern South America margin might be benefited from investigations of the sedimentary record in a number of marginal basins. The Paraíba Basin is of particular interest to discuss the post-rift evolution of the South American passive margin, because it represents the last bridge with the African plate. This work aims to analyze the post-rift sedimentary record of the onshore Paraíba Basin as a contribution to discuss the neotectonic history of the South American passive margin. Surface and subsurface data were integrated from outcrops, deep stratigraphic profiles, airborne geophysical maps and remote sensing products. The depositional and denudational processes in this basin were a result of tectonic subsidence and uplifting. Tectonics after the main rifting phase are indicated by abundant structures, including normal, reverse, and strike–slip faults, as well as folds that affected the Neogene and Late Pleistocene sedimentary deposits. The ductile and brittle deformation resulted mainly from multiple reactivations of E–W, NE–SW and NW–SE trending basement shear zones. The deformation mechanism included distension and compression under a strike–slip regime. Tectonic reactivations even during the late Pleistocene support an unsteady South Atlantic passive continental margin throughout the post–rifting stage.
URL: https://authors.elsevier.com/a/1c3Mt3ic-FNa5P
... In Tierra del Fuego Island, they form part of the Cabo Domingo Group (Malumián, 1999) and are included in the Desdémona Formation (Malumián and Olivero, 2006), the Cabo Ladrillero, Cabo San Pablo and Cabo Viamonte beds (Malumián and Olivero, 2006), and the Carmen Silva Formation (Codignotto and Malumián, 1981). In Santa Cruz Province they are represented by the Estancia 25 de Mayo Formation (Cuitiño and Scasso, 2010), and the El Chacay Formation (Chiesa and Camacho, 1995) in the Andean foothills, and by the San Julián and Monte León Formations (Bertels, 1970) in the Atlantic coast. In Chile (Fig. 2), they are included in the Guadal Formation (Niemeyer et al., 1984) in Aysén (Meseta Guadal and Chile Chico areas), and in the Estancia 25 de Mayo Formation in Magallanes (Sierra Baguales; Bostelmann et al., 2012). ...
... However, Chiesa and Camacho (1995) proposed the El Chacay Formation for the intermediate Lago Posadas region (Fig. 2). The exposures of Lago Argentino were revisited by Cuitiño and Scasso (2010) who described many sections and proposed the new name Estancia 25 de Mayo Formation. However, the original Centinela Formation name was still used by some authors in regions as separated as Lago Buenos Aires and Río Turbio. ...
... The Estancia 25 de Mayo Formation (Fig. 3B) transitionally overlies fluvial deposits of the lower Miocene Río Leona Formation and is covered transitionally by the Miocene fluvial deposits of the Santa Cruz Formation. At the southeast scarp of Lago Argentino, the Estancia 25 de Mayo Formation is about 180 m thick and consists of the lower Quién Sabe Member composed of fine to medium-grained, massive fossiliferous sandstones; and the upper Bandurrias Member composed of medium to coarse-grained sandstones with cross-bedding and intercalations of muddy to heterolithic beds (Cuitiño and Scasso, 2010;Cuitiño et al., 2012) (Fig. 3B). The Quién Sabe Member, characterized by the presence of "Ostrea" hatcheri Ortmann, represents sedimentation in a marine shelf to nearshore environment; while the Bandurrias Member, containing the marginal marine oyster Crassostrea orbignyi (Ihering), represents sedimentation in a tide-dominated estuarine environment (Cuitiño et al., 2012(Cuitiño et al., , 2013. ...
Richly fossiliferous upper Oligocene to lower Miocene Patagoniense marine deposits constitute a conspicuous feature of the sedimentary record of most basins in Patagonia. Patagoniense meaning and subdivisions have been confusing, and correlation and elucidation of factors controlling sedimentation in a region as extensive as Patagonia are still highly debated. Our revision of the distribution, correlation, stratigraphic arrangement, and timing of deposition, allows redefining the Patagoniense as a succession of widely distributed marine sediments accumulated in Patagonia from ∼25 to 15 Ma, showing different timing of accumulation for each basin. It can also be conceived as a higher rank stratigraphic cycle of relative sea-level fluctuation, which comprises two medium rank stratigraphic cycles spanning 2–4 Myr each, in turn enclosing several lower rank cycles of less than 1 Myr. The late Oligocene (∼25-23 Ma) medium rank cycle shows deposits restricted mostly to the coastal area of Tierra del Fuego and Santa Cruz provinces in the Austral-Magallanes Basin, which respond to a combination of global sea-level fluctuations and flexural subsidence. The overlying early Miocene (∼22-15 Ma) medium rank cycle comprises sediments deposited over extensive areas of Patagonia with a maximum flooding at 20-19 Ma suggesting, in addition to tectonic subsidence in the Austral-Magallanes Basin, regional long-wavelength subsidence, and a global sea level component for this episode. The timing and thickness of the regressive part of this cycle show differences for each basin, suggesting the action of local sedimentary controls such as differential rates of sediment supply. Further geochronological and stratigraphic studies are necessary, especially for the northern exposures, which will allow improving time-constrained paleogeographic reconstructions.
... In the El Calafate area (Argentina) the unit unconformably rests on top of the Man Aike Formation and, near Río Turbio (Argentina), contacts with the Río Guillermo Formation. The unit is transitionally covered by the 25 de Mayo (=Centinela) Formation (Cuitiño and Scasso, 2010). ...
Patagonia has a rich record of fossil woods that are a unique data store of paleoclimatic information. We studied the wood flora recovered from the Río Leona Formation (early Miocene) of southern Patagonia near El Calafate and Río Turbio localities, Santa Cruz Province, Argentina. The fossil wood assemblage was analyzed using various methodologies (anatomy analysis, Vulnerability and Mesomorphic indices, and the Coexistence Approach) to determine paleoclimate variables including mean annual temperature (MAT) and mean annual precipitation (MAP). The anatomy analysis developed by Wiemann et al. (1998, 1999) is based mostly on woods from the Northern Hemisphere. We applied those equations to extant woods from the southernmost region of South America to test their functionality and to compare them with the results obtained from the fossils. These equations gave limited results. Climate signals from fossil woods suggest a microthermal climate for the region with MAT of 8–12 °C and MAP of 80–170 cm/year. In addition, part of the results points towards an environment with water in abundance (i.e., Coexistence Approach and some wood characters influenced by the environment) and other results suggest wood tolerance to hydric stress (i.e., Vulnerability Index, Mesomorphy Index, and wood characters influenced by the environment). These suggest an environment with rainy and dry seasons, which is also supported by the presence of well-marked growth ring boundaries and false rings. These conditions can be found today in central Chile, a region that shares some vegetation elements with the Río Leona Formation and has a Mediterranean climate.
... The former unit crops out in the Lago Argentino area and was dated by Cuitiño et al. (2012), who proposed an 87 Sr/ 86 Sr age ranging between 20 to 19 Ma. Sand dollars are rare and recorded in the lowermost beds of the Quien Sabe Member (Estancia Quien Sabe, Estancia La Laurita), which is composed of shell beds and highly bioturbated sandstones deposited in shallow, moderately low energy environments (Cuitiño & Scasso, 2010). The recognized scutelliforms are I. patagonensis and "Iheringiella" sp. ...
Scutelliforms were diverse and widespread in shallow marine environments during Neogene times in South America. Nevertheless, they have almost never been used as biostratigraphic tools.
Objective: To provide a refined stratigraphic frame useful for calibrating temporal dimensions of scutelliform diversity from Argentina and Uruguay and its correlation with the molluscan assemblages previously proposed.
Methods:A detailed survey of their geographic and stratigraphic provenance was carried out. We revised both the bibli�ography and collections (institutional and from our own field work). Results: The group is represented by 14 species belonging to six genera, and four assemblages were identified. Numerical dates of the Neogene marine
rocks obtained recently allowed their placement in a chronological scheme: “Iheringiella” sp. A is restricted to the late Oligocene, the genera Camachoaster and “Eoscutella” and the species Monophoraster telfordi to the early Miocene, Abertella gualichensis and Abertella miskellyi to the middle Miocene, and Monophoraster duboisi, Amplaster coloniensis and Amplaster ellipticus to the late Miocene. Non-lunulate scutelliforms are not restricted to the late Oligocene as previously supposed. The oldest occurrence of the genus Monophoraster cor�responds to the early Miocene, and along with Iheringiella are long-living taxa that embrace the 25.3 Ma-18.1 Ma (Iheringiella patagonensis) and approximately 15 Ma-6.48 Ma (Monophoraster darwini) intervals. The presence of Iheringiella in the early Miocene of northeastern Patagonia is corroborated, reaching there its north�ernmost distribution. Monophoraster darwini has a temporal range from the late Miocene (where it was previ�ously thought to be restricted) back to the middle Miocene, since this is the species yielded in the well-known and discussed “Monophoraster and Venericor Beds”. Conclusions: The Paleogene-Neogene scutelliforms of Argentina and Uruguay range from the late Oligocene to the late Miocene. There is a good orrespondence among the numerical ages, molluscan biozones and scutelliform assemblages.
... Most previous workers have proposed an upper Eocene to early Oligocene age for the Río Guillermo Formation [98][99][100]. Fluvial sedimentation in the Magallanes-Austral Basin was briefly interrupted by a shallow marine incursion, resulting in sandstone and mudstone deposits of the Estancia 25 de Mayo Formation [57,58,101] and coeval informal units ("Estratos de Río del Oro"). This unit has been correlated to the distal Monte León Formation along the Atlantic coast that, together, records the Leonense marine incursion of the Patagonian Sea at this latitude [56,59,60,62]. ...
... Fluvial sedimentation was temporarily disrupted by flooding of the foreland basin by the Leonense marine incursion [56,57,60,62,101], which may have been further enhanced by subsidence loading during Toro thrust faulting ( Figure 6). Resumed fluvial deposition of the Santa Cruz Formation is classically cited as the molasse deposits of the main phase of early Miocene Andean orogenesis and surface uplift (e.g., [54,99,102,104,105]). Published detrital geochronology from the overlying early Miocene Santa Cruz Formation yields dominantly (>70%) Late Cretaceous zircons [29]. ...
New detrital zircon U-Pb geochronology data from the Cenozoic Magallanes-Austral Basin in Argentina and Chile ~51° S establish a revised chronostratigraphy of Paleocene-Miocene foreland synorogenic strata and document the rise and subsequent isolation of hinterland sources in the Patagonian Andes from the continental margin. The upsection loss of zircons derived from the hinterland Paleozoic and Late Jurassic sources between ca. 60 and 44 Ma documents a major shift in sediment routing due to Paleogene orogenesis in the greater Patagonian-Fuegian Andes. Changes in the proportion of grains from hinterland thrust sheets, comprised of Jurassic volcanics and Paleozoic metasedimentary rocks, provide a trackable signal of long-term shifts in orogenic drainage divide and topographic isolation due to widening of the retroarc fold-thrust belt. The youngest detrital zircon U-Pb ages confirm timing of Maastrichtian-Eocene strata but require substantial age revisions for part of the overlying Cenozoic basinfill during the late Eocene and Oligocene. The upper Río Turbio Formation, previously mapped as middle to late Eocene in the published literature, records a newly recognized latest Eocene-Oligocene (37-27 Ma) marine incursion along the basin margin. We suggest that these deposits could be genetically linked to the distally placed units along the Atlantic coast, including the El Huemul Formation and the younger San Julián Formation, via an eastward deepening within the foreland basin system that culminated in a basin-wide Oligocene marine incursion in the Southern Andes. The overlying Río Guillermo Formation records onset of tectonically generated coarse-grained detritus ca. 24.3 Ma and a transition to the first fully nonmarine conditions on the proximal Patagonian platform since Late Cretaceous time, perhaps signaling a Cordilleran-scale upper plate response to increased plate convergence and tectonic plate reorganization.
