Mechanisms of Subsidence and Uplift of Southern Patagonia and Offshore Basins During Slab Window Formation

Abstract

Subduction of bathymetric anomalies (e.g., an active ridge) can alter the morphology of subducted slabs and their coupling to surface processes. A natural laboratory to study these effects is the subduction of the Oceanic Chilean Ridge beneath the South American plate, which led to the formation of the Patagonian slab window. Its formation and subsequent northward migration contributed to the regression of Patagoniense sea and exhumation of marine strata to their present elevation. To date, there is no quantitative analysis of the effects on the sediment routing system of the slab window. We modeled the Neogene topographic change and foreland sedimentary evolution from the Andean Cordillera to Atlantic margin. Our results show that subcrustal‐driven subsidence correlated with accelerated subduction of the Nazca plate is required to explain the timing of the Patagonian transgression and thickness and spatial extent of marine beds during the incursion. In other words, traditional mechanisms, such as foreland flexure and global sea‐level rise, are insufficient. The subsequent regression and accumulation of mid‐Miocene alluvial‐fluvial deposits were associated with the growth of the Cordillera and a possible flattening of Nazca subduction in the middle Miocene. Isostatic uplift of ∼1 km due to lithospheric thinning during slab window formation can explain the foreland exhumation, sediment bypass, and increases in the offshore sedimentation rate. However, spatial‐temporal varying dynamic uplift is required to explain the along‐strike variations in foreland sedimentation. Our study provides new insights into the interplay between slab window formation, crustal deformation, and landscape evolution.

Cenozoic subsidence‐driving mechanisms in the southernmost Patagonian basins of Tierra del Fuego and SW Atlantic

“…This could be explained as uplift driven by subcrustal forces, contemporaneously with Andean thrusting. This can be alternatively explained by erosion-driven rebound as recently shown by Ding et al (2023).…”

“…The only terrestrial records are represented by thin alluvial strata deposited in the early to middle Miocene (Malumián & Olivero, 2006). North of 52° S, in contrast, the palaeoenvironments were locally marine (particularly in the southern sections) to transitional in the Latest Cretaceous to Palaeocene (Gallardo Jara et al, 2022) to dominantly fluvial in the Miocene (Cuitiño et al, 2019, Rivera et al, 2020, with two shallow marine flooding episodes associated with dynamic subsidence (Dávila et al, 2019;Ding et al, 2023;Ghiglione et al, 2019;Gianni et al, 2018;Navarrete et al, 2020). Recent compilations also show thicker stratigraphic columns to the south (Ghiglione et al, 2019).…”

“…The latter was related to long-wavelength mantle-driven uplift that affected the whole orogenic and foreland areas (Ávila et al, 2023;Ávila & Dávila, 2020;Ding et al, 2023). However, these four stages (and sub-stages that characterize each episode) were not homogeneous and, particularly, were diachronous along strike (Dávila et al, 2018;Guillaume et al, 2013;Stevens Goddard & Fosdick, 2019).…”

Testing Mantle Convection Simulations With Paleobiology and Other Stratigraphic Observations: Examples From Western North America

“…There now exists a considerable body of mantle convection simulations, a few of which have been compared to independent geological observations at specific localities (e.g., New Jersey Margin, North America; Flament et al., 2013) and to global power spectra of ocean age‐depth residuals (Hoggard et al., 2016). Model predictions, such as uplift and subsidence, have recently been coupled with models of lithospheric and landscape evolution to predict development of drainage networks and sedimentary basins (e.g., Ding et al., 2023; Faccenna et al., 2019; Salles et al., 2017; Wang et al., 2020).…”

Geodynamic and Climatic Forcing on Late‐Cenozoic Exhumation of the Southern Patagonian Andes (Fitz Roy and Torres del Paine massifs)

“…The slab window opened through subduction of oceanic spreading ridge segments approximately parallel to the trench, migrating northward from an initial junction around 54°S at 16 Ma to about 49°S at 12 Ma, and 47°S at 3 Ma (Figure 1) (Breitsprecher & Thorkelson, 2009;Cande & Leslie, 1986;Fosdick et al, 2013;Georgieva et al, 2016Georgieva et al, , 2019Guillaume et al, 2009Guillaume et al, , 2013Haschke et al, 2006;Lagabrielle et al, 2010;Ramos, 2005;Scalabrino et al, 2010;Stevens Goddard & Fosdick, 2019;Thomson et al, 2001). Among the effects of oceanic ridge subduction are the inception of retroarc volcanism and cessation of arc volcanism, reduction in shortening, and regional surface and rock uplift (Ávila & Dávila, 2020;Ávila et al, 2023;Ding et al, 2023;Guillaume et al, 2009Guillaume et al, , 2013Lagabrielle et al, 2004Lagabrielle et al, , 2010Ramos, 2005;Scalabrino et al, 2010;Stevens Goddard & Fosdick, 2019). Mantle upwelling during oceanic ridge subduction is expected to have generated long-wavelength dynamic and isostatic surface uplift and eastward tilting of the continent, following the northward motion of the CTJ (Ávila & Dávila, , 2020Ávila et al, 2023;Ding et al, 2023;Guillaume et al, 2009Guillaume et al, , 2013.…”