Tectonosedimentary evolution of the Coastal Cordillera and Central Depression of south-Central Chile (36°30′-42°S)

Encinas, Alfonso; Sagripanti, Lucía; Rodríguez, M. H.; Orts, Darío; Anavalón, A.; Giroux, P.; Otero, J.; Echaurren, Andrés; Zambrano, Patricio; Valencia, Víctor A.

doi:10.1016/j.earscirev.2020.103465

Cited by 16 publications

(10 citation statements)

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“…12; see also Menant et al, 2020, and references therein). Alternatively, Encinas et al (2020) noted that the uplift of the Coastal Cordilleras in south-central Chile may be decreased where a strongly hydrated seafloor (such as a fracture zone) is subducted under the wedge (in line with previous geophysical data from Moreno et al [2014]). Although debated, the question of the critical role of deep accretionary processes on the formation of these coastal promontories deserves to be addressed, notably through further geophysical investigations (e.g., Bassett and Watts, 2015).…”

Section: Research Papersupporting

confidence: 63%

“…These include (1) GPS measurements, (2) measurement of uplift of geomorphological features encompassing marine terraces and fluvial incisions, (3) analysis of stratigraphic records in forearc basins, and (4) low-temperature thermochronology. Enhanced uplift rates have thus been locally evidenced all along the Pacific realm and interpreted as a consequence (at least partly) of deep accretionary events, e.g., at Hikurangi (Walcott, 1987;Litchfield et al, 2007;Houlié and Stern, 2017), Nankai (Hasebe and Tagami, 2001), Cascadia (Brandon et al, 1998;Pazzaglia and Brandon, 2001), Costa Rica (Fisher et al, 1998), southern Peru (Regard et al, 2021), northern Chile (Hartley et al, 2000;Clift and Hartley, 2007), and south-central Chile (Glodny et al, 2005;Saillard et al, 2009;Encinas et al, 2012Encinas et al, , 2020. This interpretation is supported by analogue and numerical experiments (Gutscher et al, 1996;Ellis et al, 1999;Lohrmann et al, 2006;Litchfield et al, 2007), but it is also worth noting that other mechanisms occurring at very different time scales contribute to vertical motions of the upper plate.…”

Section: Surface Expression Of Ongoing Basal Accretionmentioning

confidence: 99%

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The rise and demise of deep accretionary wedges: A long-term field and numerical modeling perspective

2021

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Several decades of field, geophysical, analogue, and numerical modeling investigations have enabled documentation of the wide range of tectonic transport processes in accretionary wedges, which constitute some of the most dynamic plate boundary environments on Earth. Active convergent margins can exhibit basal accretion (via underplating) leading to the formation of variably thick duplex structures or tectonic erosion, the latter known to lead to the consumption of the previously accreted material and eventually the forearc continental crust. We herein review natural examples of actively underplating systems (with a focus on circum-Pacific settings) as well as field examples highlighting internal wedge dynamics recorded by fossil accretionary systems. Duplex formation in deep paleo–accretionary systems is known to leave in the rock record (1) diagnostic macro- and microscopic deformation patterns as well as (2) large-scale geochronological characteristics such as the downstepping of deformation and metamorphic ages. Zircon detrital ages have also proved to be a powerful approach to deciphering tectonic transport in ancient active margins. Yet, fundamental questions remain in order to understand the interplay of forces at the origin of mass transfer and crustal recycling in deep accretionary systems. We address these questions by presenting a suite of two-dimensional thermo-mechanical experiments that enable unravelling the mass-flow pathways and the long-term distribution of stresses along and above the subduction interface as well as investigating the importance of parameters such as fluids and slab roughness. These results suggest the dynamical instability of fluid-bearing accretionary systems causes either an episodic or a periodic character of subduction erosion and accretion processes as well as their topographic expression. The instability can be partly deciphered through metamorphic and strain records, thus explaining the relative scarcity of paleo–accretionary systems worldwide despite the tremendous amounts of material buried by the subduction process over time scales of tens or hundreds of millions of years. We finally stress that the understanding of the physical processes at the origin of underplating processes as well as the forearc topographic response paves the way for refining our vision of long-term plate-interface coupling as well as the rheological behavior of the seismogenic zone in active subduction settings.

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Section: Research Papersupporting

confidence: 63%

Section: Surface Expression Of Ongoing Basal Accretionmentioning

confidence: 99%

The rise and demise of deep accretionary wedges: A long-term field and numerical modeling perspective

2021

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“…1 and 4). Notably, this distance could be larger if forearc fold-and-thrust belts are present as recently recognized in some areas of the Andes (e.g., Armijo et al 2015;Riesner et al, 2018;Martinez et al, 2020;Encinas et al, 2020). Volcanic arcs and accretionary prisms do not superpose even in subduction settings with the highest known slab angles, such as Mariana-type subduction zones with up to 90° dipping slabs (Uyeda and Kanamori, 1979).…”

Section: Discussionmentioning

confidence: 93%

The late Paleozoic paired metamorphic belt of southern Central Chile: Consequence of a near-trench thermal anomaly?

Gianni¹

2021

Preprint

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The hypothesis of a subduction-related Miyashiro-type paired metamorphic belt for the origin of the late Paleozoic igneous and metamorphic complex in the Andean Coastal Cordillera has remained unquestioned since its proposal in the early seventies. A synthesis of the advances in the study of these metamorphic rocks between 33°S and 42°S, revising field relations among geological units, and geochemical and geochronological data from the contemporaneous granitoids of the Coastal Batholith, highlights inconsistencies in this model. The record of short-lived forearc magmatism in the late Paleozoic intruding the partially synchronous accretionary prism, and geochemical and isotopic data from the igneous rocks indicating sources from the accretionary prism sediments and the back-top lithosphere, suggest a departure from typical subduction settings. I conclude that the anomalous configuration of the paired metamorphic belt and the associated Coastal Batholith resulted from a complex geodynamic process involving a near-trench thermal anomaly caused by the subduction of a trench parallel mid-ocean ridge.

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“…The Coastal Cordillera (fig. 2) is a low-profile mountain range, with maximum elevations reaching around ~1500 m (Encinas et al, 2021). It primarily consists of upper Paleozoic-Triassic metamorphic rocks and Carboniferous-Permian plutonic rocks (Sernageomin, 2003).…”

Section: Regional Geologic Characteristicsmentioning

confidence: 99%

Cenozoic Basin Evolution During Alternating Extension and Shortening in the Southern Central Andes Along the Chile-Argentina Border, 37–38°S

Encinas,

Rosselot,

Sagripanti

et al. 2024

American Journal of Science

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The south-central Chile and Argentina margin experienced a regional phase of extensional tectonics during the Oligocene–early Miocene, forming several basins across the forearc, Andean Cordillera, and retroarc regions. These basins accumulated thick successions of volcanic and sedimentary rocks. Subsequently, Neogene contractional tectonics led to the development of the current Andean Cordillera and the deposition of synorogenic clastic deposits in foreland basins. Traditionally, the Cura Mallín Formation, comprising a lower volcanic unit (CMV) and an upper sedimentary unit (CMS), has been interpreted to have formed during the Oligocene–early Miocene extensional phase. However, some studies propose deposition of the CMS in a foreland basin during the early–late Miocene. To unravel the transition from extensional to contractional tectonics in the Andes of south-central Chile and Argentina, we conducted new geochronological analyses (U-Pb, LA-ICP-MS) and integrated these results with structural, stratigraphic, and sedimentological observations in key sections within the CMS and the overlying Trapa-Trapa Formation in the Principal Cordillera along the Chile-Argentina border (37°–38°S). Our findings indicate that only the lower part of the CMS was deposited in an extensional setting, as evidenced by the presence of an inverted extensional wedge dated at ∼20 Ma. The middle-upper CMS (∼19 to 9 Ma) and contemporaneous units to the east exhibit evidence of syncontractional deformation, suggesting deposition in a foreland basin generated by shortening of the western Principal Cordillera. Around 9 Ma, uplift of the Agrio and Chos Malal fold and thrust belts, east of the Principal Cordillera, led to segmentation of the foreland basin. The Trapa Trapa Formation was deposited in a hinterland basin, with sediment sourced from the east. After ∼6.5 Ma, major contractional deformation shifted westward, resulting in intense folding of the CMS and Trapa Trapa Formation and subsequent thrusting of the western Principal Cordillera over the Central Depression. Our study suggests that deformation progressed toward the eastern foreland during the early to late Miocene and then shifted toward the western forearc during the late Miocene to Pleistocene.

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Tectonosedimentary evolution of the Coastal Cordillera and Central Depression of south-Central Chile (36°30′-42°S)

Cited by 16 publications

References 75 publications

The rise and demise of deep accretionary wedges: A long-term field and numerical modeling perspective

The rise and demise of deep accretionary wedges: A long-term field and numerical modeling perspective

The late Paleozoic paired metamorphic belt of southern Central Chile: Consequence of a near-trench thermal anomaly?

Cenozoic Basin Evolution During Alternating Extension and Shortening in the Southern Central Andes Along the Chile-Argentina Border, 37–38°S

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