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Conceptual geohistory representation of backstripped tectonic subsidence (red/yellow) and total basin subsidence (black/gray curve). The component of subsidence due to sedimentary loading is the difference between the tectonic subsidence and total subsidence curves (after Van Hinte (1978)). Uncertainty bands represent the range of calculated subsidence values for the range of paleo sea‐depth estimates.
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Backstripped tectonic basin subsidence histories are critical for interpreting phases of lithospheric deformation and paleoenvironmental change from the stratigraphic record. This study presents new subsidence modeling of the Rocas Verdes Backarc Basin (RVB) and Magallanes‐Austral retroarc foreland basin (MAB) of southernmost South America to evalu...
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All changes taking place in a watershed have repercussions on lacustrine environments, being these, the sink of all activities occurring in the basin. Lake Titicaca, the world’s highest and navigable lake, is not unfamiliar with these phenomena that can alter the sedimentation dynamics and metal accumulation. This study aimed to identify temporal t...
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... Turbidites of the Upper Cretaceous Punta Barrosa Formation reflect the onset of deep-water, coarse-clastic sedimentation in the Magallanes Basin, signifying an inversion of the Rocas Verdes Basin and consequent subsidence of the Magallanes foreland basin (Wilson, 1991;Fildani et al., 2003;Fildani and Hessler, 2005;Fosdick et al., 2011;Ghiglione et al., 2015;Malkowski et al., 2017b;VanderLeest et al., 2022). U-Pb detrital zircon ages from the Punta Barrosa Formation constrain the timing of coarse-clastic deposition and basin inversion to no later than 92 Ma (Turonian) at 51°S (Fildani et al., 2003). ...
Analyzing how provenance signatures of tectonically complex ancient sedimentary basins vary between the outcrop and the subsurface provides a more complete sediment provenance history. The 500+-km-long outcrop belt of the Rocas Verdes and the Magallanes-Austral Basins in southern Patagonia and its subsurface to the east allow us to constrain relationships between longitudinal and transverse sediment sources feeding the basin. New detrital zircon U-Pb ages (n = 2558) from nine subsurface core samples from the Springhill, Piedra Clavada, and La Anita Formations along a 140 km E-W seismic reflection transect (50°S, 71.5°W–69.5°W) reveal the provenance of the basin’s eastern subsurface extent and the influence that tectonic activity can have on sediment capture. Detrital zircon ages (n = 1068) were also collected from four outcrop Springhill Formation samples 140 km NW from the transect near Lago San Martín. Maximum depositional ages (MDAs) from the Springhill Formation cores range from 159 to 157 Ma, which are older than correlative outcrop ages of 151–148 Ma. MDAs from the Piedra Clavada and La Anita Formations range from 93.7 to 91.5 Ma and from 79.3 to 78.3 Ma, respectively, and overlap in age or are slightly younger than outcrop ages. The unimodal Late Jurassic age distribution from the Springhill Formation suggests that it almost exclusively was sourced by recycling of the underlying El Quemado Complex. Early–Middle Jurassic ages in the Early Cretaceous Piedra Clavada Formation samples suggest the basin was either sourcing from the North Patagonian Massif to the N-NE and from the Deseado Massif to the NE or recycling exhumed volcaniclastic sequences in the northern margin of the basin. By the Late Cretaceous, the basin fill was more locally sourced, as suggested by the muted abundance of Early–Middle Jurassic ages in La Anita Formation samples and a second mode of Late Jurassic–Early Cretaceous ages locally derived from recycling of the exhumed El Quemado Complex from the Patagonian fold-and-thrust belt. We suggest that the latitudinal and local transverse drainages that sourced the Magallanes-Austral Basin outcrop belt also fed the eastern, subsurface extent of the basin. Results of this work highlight the importance of using several types of provenance methods and a three-dimensional approach to study the erosional history of sedimentary basins.
... The regional Paleogene unconformity that is commonly associated with that event that, in the study area presents hiatuses of ~60 Myr and ~43 Myr (Cerro Fortaleza -Cerro Hornos Formations contact and Cerro Fortaleza -Man Aike Formations contact respectively, Sickmann et al., 2018). To the south the temporal hiatus is smaller, finding in the Última Esperanza and Río Turbio regions a time gap that shortens to ~15 Myr (Fosdick et al., 2020;George et al., 2020;VanderLeest et al., 2022;Albano et al., 2023). Thermochronological studies also indicate an Eocene exhumation event possibly related to compression with out-of-sequence fault activation in the Ultima Esperanza and Rio Turbio region (Fosdick et al., 2013, Stevens Goddard et al., 2023. ...
This paper focuses on the analysis of the Southern Patagonian fold-thrust belt at ca. 50◦ SL, employing a kinematic-structural approach that makes it possible to define its step-by-step structural evolution. Seismic interpretation is combined with outcrop structural data to provide the basis for an integrated evolutionary model including a Jurassic extensional stage, followed by contraction events since the Late Cretaceous. Our interpretation and results reveal a hybrid fold-thrust belt system, with a high decoupling between basement structures and the sedimentary cover. The basement is deformed by tectonic inversion of the Jurassic rift fault system and duplex stacking geometries, while the sedimentary cover is folded by the action of predominantly west-vergent low-angle faults. The Jurassic rifting model identifies listric faults with detachment depths ranging from ~ 6000 to ~ 6500 m.a.s.l. and 11 % – 14 % magnitude extension. Shortening calculations yield values of less than 6 %.
Growth strata and thickness variations in Cretaceous units suggest that part of the shortening occurred during the
Coniacian/Santonian. Overall, this research contributes to the knowledge of fold-thrust belts, highlighting the importance of doing a comprehensive structural modeling including previous deformational stages, and describing steps to provide reliable measurements of deformation.
... Furthermore, similar to many Precambrian successions, some Phanerozoic offshore basins are also poorly constrained due to limited biostratigraphic or radiometric age control, so these successions would be ideal targets for our model. Overall, we suggest that the incorporation and propagation of uncertainties, as demonstrated in this study, are critical for the field of quantitative basin analysis, even in well-characterized and well-dated Phanerozoic basins, since the combination of better-quantified parameters and uncertainty treatments ultimately yields better geological insights (e.g., VanderLeest et al., 2022). ...
... (b) Could erosion associated with a regional Paleogene unconformity in the retroarc foreland basin extend beyond the basin boundary and into the orogenic belt? Currently, there is no documented evidence of erosion during the Paleogene unconformity in the southern Patagonian Andes beyond the western edge of the foreland basin system; however evidence of concurrent exhumation in the batholith or thrust belt could help to determine the process responsible for this major regional erosion event (Fosdick et al., 2015;George et al., 2020;VanderLeest et al., 2022). (c) Is there evidence of Farallon-Aluk spreading ridge subduction along the western plate margin in the early to middle Eocene as proposed by tectonic plate reconstructions (Cande & Leslie, 1986;Eagles & Scott, 2014;Somoza & Ghidella, 2012)? ...
Thermochronologic results from zircon fission track and (U‐Th)/He data collected across the Patagonian batholith, basement and thrust belt of the southern Patagonian Andes between 51°S and 53°S resolves new spatiotemporal patterns of Paleogene rock cooling that allows us to reconstruct deformational and erosional events along‐ and across‐strike. Our study applies a novel modeling strategy, the Path Family Approach, to filter geologically plausible thermal solutions from inverse modeling results for rocks in this study according to a sample's structural and tectonic context. Our results identify minimal cooling and interpreted exhumation of batholith rocks throughout the Paleogene. However, in the western domain we identify synchronous cooling of Jurassic volcaniclastic rocks in the thrust belt both along‐ and across‐strike between 50 and 35 Ma, which we interpret as a period of out‐of‐sequence deformation that coincides with the start of a distinct period of orogenesis in the Fuegian Andes (54°S). This finding may suggest that the southern Patagonian Andes and Fuegian Andes evolved as a connected orogenic system along the bend of the Patagonian orocline. In the central domain, modeled cooling of thermally reset Cretaceous basinal strata from 60 to 50 Ma corresponds to a well‐recognized erosional unconformity in the adjacent Cenozoic foreland depocenter, indicating that contemporaneous exhumation occurred beyond the margins of the basin. Although not diagnostic, exhumation within the orogenic belt, beyond the Cenozoic foreland basin, provides a new regional context to interpret the cause of this regional erosion event. Collectively these results inform the Paleogene tectonic evolution of the orogen.
... A basin-wide unconformity between Cretaceous and Paleogene units could be related with that tectonic event as a response of dynamic uplift or crustal shortening (George et al., 2020). The unconformity decreases in magnitude to the south from ~60 Myr hiatus at Lago Viedma latitude to ~15 Myr at Lago del Toro latitude (Fosdick et al., 2015Sickmann et al., 2018;George et al., 2020;VanderLeest et al., 2022). The last important orogenic event in the Southern Patagonian Andes is associated with the subduction of the Chile Ridge oceanic spreading center beneath South America, which started ~14 Ma at ~54° S and migrated northwards to its current position at 46°S (Forsythe et al., 1986;Ramos, 2005, Stevens Goddard andFosdick, 2018). ...
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.
... A basin-wide unconformity between Cretaceous and Paleogene units could be related with that tectonic event as a response of dynamic uplift or crustal shortening (George et al., 2020). The unconformity decreases in magnitude to the south from ~60 Myr hiatus at Lago Viedma latitude to ~15 Myr at Lago del Toro latitude (Fosdick et al., 2015Sickmann et al., 2018;George et al., 2020;VanderLeest et al., 2022). The last important orogenic event in the Southern Patagonian Andes is associated with the subduction of the Chile Ridge oceanic spreading center beneath South America, which started ~14 Ma at ~54° S and migrated northwards to its current position at 46°S (Forsythe et al., 1986;Ramos, 2005, Stevens Goddard andFosdick, 2018). ...
(Open-access article available at: http://dx.doi.org/10.1016/j.earscirev.2024.104912)
Global sedimentary hiatuses are well-documented in ancient pelagic sediment, and include Paleocene, Eocene-Oligocene boundary, and Miocene hiatuses. Less clear is the extent of these hiatuses in continental margin settings. Here, we test the hypothesis that global hiatuses evident in pelagic sections are also manifested in siliciclastic basins of continental margins globally. We choose to focus on the Eocene greenhouse to Oligocene icehouse transition, a period that is remarkable as the most profound climatic transition of the Cenozoic, and a period characterized by extreme cooling and expansion of polar ice, sea-level fall, and global changes to ocean circulation. We perform a comprehensive review of marine siliciclastic basin literature to produce a global inventory of Eocene-Oligocene unconformities. We find evidence for a prominent Eocene-Oligocene unconformity in sedimentary basins along the margins of every continent. The globally-widespread distribution of unconformities suggests global controls on their development. Furthermore, Eocene-Oligocene erosion surfaces are common in shelf settings, as well as in deep-water settings from slope to basin floor, indicating unconformity-generating processes across a wide range of water depths. Global sea-level fall may have driven subaerial shelf exposure and erosive down-slope processes including submarine canyon cutting and mass wasting. Meanwhile, the intensification of deep-ocean thermohaline currents potentially induced erosion of not only pelagic successions, but also of clastic successions. Overall, our documentation of globally-widespread Eocene-Oligocene unconformities suggests global controls, of which the extreme climatic and oceanographic changes of the greenhouse to icehouse transition seem particularly compelling.
We report uplift and shortening rates from a late Neogene–Pleistocene deformation stage of the frontal fold-thrust belt and adjacent wedge-top in the Principal Cordillera of the southern Central Andes (33-39° SL). A structural model is presented based on integration of surface field data and subsurface 2D seismic sections. Shortening, uplift, and sedimentation rates were calculated from different steps of kinematic modelling. Our structural interpretations and modelling are integrated with new detrital zircon U-Pb geochronology to define a previously overlooked Pleistocene period of orogenic shortening and syntectonic sedimentation in the Malargüe basin. This task was possible due to the dating of three samples yielding between ∼12 and 1 Ma obtained from a 900 m deep well located in the foreland. From stratigraphic correlations, our data records an active Plio-Pleistocene wedge-top depozone coeval with retreat of the volcanism, and the emplacement of retroarc basalts. Structural modelling, together with detrital zircon U-Pb provenance data register shortening producing a foredeep to wedge-top Plio-Pleistocene transition, adjusting and completing the knowledge of the frontal fold-thrust belt and foreland basin in the southern Central Andes.
Supplementary material: https://doi.org/10.6084/m9.figshare.c.7033425
