Andean Growth Research Articles

The transition from backarc extension to Andean growth: Insights from geochronologic, sedimentologic, and structural studies of Mesozoic and Cenozoic sedimentary and volcanic rocks in south-central Chile (36°S)

Many studies propose a significant shift in the tectonic and paleogeographic evolution of the Andes in south-central Chile and Argentina during the Late Cretaceous. It has been proposed that the preceding Jurassic-Early Cretaceous extensional regime that resulted in a low-relief volcanic arc and the backarc Neuquén basin came to an end, giving way to shortening and Andean growth from the Late Cretaceous onward. Nevertheless, there are disagreements regarding the timing and nature of this transition to Andean orogenesis. To address these issues, we conducted geochronologic (U–Pb and 40Ar/39Ar), sedimentologic, and structural studies on Mesozoic-Cenozoic sedimentary and volcanic rocks in the Río Maule area (Principal Cordillera, Chile, 36°S). From our findings and prior analyses, we propose the following tectono-stratigraphic evolution of the region. (1) Marine deposition of the Tithonian-Hauterivian Baños del Flaco Formation took place in an extensional backarc basin. (2) After a ∼ 40 Myr hiatus, fluvial deposits of the Colimapu Formation and volcanic rocks of the Plan de los Yeuques Formation accumulated during the Cenomanian-Danian. Whereas the Colimapu Formation displays evidence of syndepositional shortening, the Plan de los Yeuques Formation exhibits synextensional growth strata. Contrary to other studies, our results suggest that the Chilean part of the Principal Cordillera was largely a zone of active deposition rather than an elevated fold-thrust belt during the Late Cretaceous. We propose that sedimentation occurred within a series of relatively stable intermontane subbasins generated by shortening, followed by extension. (3) After a ∼ 20 Myr hiatus, middle Eocene to early Miocene (Lutetian-Aquitanian) accumulation of a thick succession of andesitic lavas and minor clastic sediments of the Abanico Formation occurred in an intraarc extensional basin. (4) Finally, major shortening and uplift of previously deposited Mesozoic-Cenozoic rocks took place throughout the Neogene. This phase constituted the primary contractional deformation in the Andes of south-central Chile and Argentina. In terms of the transition to early Andean deformation, we propose that structural deformation did not generate a major, regional-scale fold-thrust belt during the late Albian-Santonian. Modest extension, tectonic quiescence, or low-magnitude shortening seem to have dominated during the early to middle Cenozoic.

A petrological and structural assessment of mafic dike swarms in the Patagonian fold-thrust belt during seismic ridge collision

Between Viedma and San Martín lakes, in an area of 1200 km2 that partly covers the Southern Patagonian cordillera and the Miocene-Pliocene extra-Andean basaltic plateaus, mafic dike swarms crop out which have not been studied previously. As a result of mapping on satellite images and in the field more than 1500 dikes were identified. The dikes crop out in a zone between rear-arc calc-alkaline intrusions to the west and tholeiitic-alkaline plateau basalts to the east, within the internal and external fold-thrust belt. In order to understand the genetic relationship between the dikes, other igneous units in the region and the structures of the Andean orogeny, a petrological study (including petrography and geochemistry) and a structural analysis of the dike orientations were carried out. The dikes were emplaced close to the surface (<1 km). Three predominant compositions were recognized: basalts, which predominate, followed by tephrites and andesites, the latter restricted to a single sector. We propose preliminarily the following correlations: (i) the dikes of tephritic composition with the Río Carbón Essexite (Eocene), (ii) the andesites with the Chaltén Adakite (Miocene) and (iii) the basaltic dikes with the Pliocene basaltic plateaus. All these units are related in the literature to different stages of ridge subduction and slab window development. The dikes present variable, but not random, preferential orientations, with no relation with composition. Our analysis suggests that dike emplacement was controlled by previous anisotropies in a heterogeneous and very shallow crust. The anisotropy in the internal fold-thrust belt was achieved mainly during Eocene and/or Late Cretaceous contraction, whereas that in the external fold-thrust belt was developed during a less significant Miocene compressive event, thus resulting in a more homogeneous dike orientation. The vertical disposition of the dikes indicates horizontal stretching, as previously proposed for the last stages of Andean growth.

Southward expanding plate coupling due to variation in\xa0sediment subduction as a cause of Andean growth

Growth of the Andes has been attributed to Cenozoic subduction. Although climatic and tectonic processes have been proposed to be first-order mechanisms, their interaction and respective contributions remain largely unclear. Here, we apply three-dimensional, fully-dynamic subduction models to investigate the effect of trench-axial sediment transport and subduction on Andean growth, a mechanism that involves both climatic and tectonic processes. We find that the thickness of trench-fill sediments, a proxy of plate coupling (with less sediments causing stronger coupling), exerts an important influence on the pattern of crustal shortening along the Andes. The southward migrating Juan Fernandez Ridge acts as a barrier to the northward flowing trench sediments, thus expanding the zone of plate coupling southward through time. Consequently, the predicted history of Andean shortening is consistent with observations. Southward expanding crustal shortening matches the kinematic history of inferred compression. These results demonstrate the importance of climate-tectonic interaction on mountain building.

Coupled Andean Growth and Foreland Basin Evolution, Campanian–Cenozoic Bagua Basin, Northern Peru

AbstractCenozoic sedimentary rocks of the intermontane Bagua Basin record the Andean orogenic history of northern Peru at ~4–7°S. The northern Peruvian Andes define the northern termination of the Central Andes and are comprised of a narrow, low‐elevation orogen relative to the rest of the Central Andes. New stratigraphic and sedimentologic field observations, subsidence analysis, and detrital zircon provenance analysis enable reconstruction of the regional tectonic history. Late Cretaceous to Paleocene detrital zircon U‐Pb age spectra from the Fundo El Triunfo and Rentema formations reveal active volcanism in the Western Cordillera as early as ~80 Ma and early exhumation of Mesozoic rocks in a nascent Marañon Fold‐Thrust Belt. Eocene fluvial deposits of the Cajaruro Formation record a progressive increase in shortening and volcanism in the Western Cordillera. The upper Eocene–middle Miocene fluvial succession of the Sambimera Formation records deposition in a proximal foredeep setting. Sambimera deposits contain syndepositional detrital zircon U‐Pb age populations that reveal a major Cenozoic magmatic source in the west. An erosive boundary separates the Sambimera from the overlying San Antonio Formation. The San Antonio Formation was deposited in an intermontane basin associated with uplift of the Eastern Cordillera at these latitudes. These results highlight a foreland progression of fold‐thrust deformation, with shortening concentrated in the Western Cordillera from latest Cretaceous to middle Miocene time. We suggest that the late Miocene transition to intermontane deposition in the Bagua Basin marks initial exhumation during shortening of the Eastern Cordillera in northern Peru.

Northward propagation of Andean genesis: Insights from Early Cretaceous synorogenic deposits in the Aysén-Río Mayo basin

Decoding the earliest orogenic stages in the Andes, the largest subduction orogen on Earth is fundamental to understanding changes in climate, drainage organization, and biodiversity in South America. Furthermore, it is crucial to unraveling the driving mechanism behind the initiation of orogeny. To track the earliest stages of Andean growth, we studied the Aysén/Río Mayo basin (ARB) in the North Patagonian Andes. The small degree of Cenozoic tectonic overprinting in this part of the Andes has allowed outstanding preservation of the deformational and sedimentary record of the earliest Andean deformation. In this study, we employ a multidisciplinary approach involving structural geology, sedimentology, geochronology, and provenance studies from the Early Cretaceous Apeleg Formation (~130–122 Ma) in the ARB and geochemical analysis of intrusive Cretaceous igneous rocks. Particularly, the recognition of syncontractional growth strata at several localities indicate a syntectonic origin for this unit and provide additional structural evidence of Early Cretaceous contraction in the North Patagonian Andes. Thus, the Apeleg Formation is interpreted as deposited during a contractional basin stage. Geochemical data from Aptian-Albian intrusive igneous rocks indicate that initial contraction emplaced over thinned crust likely inherited from the Jurassic extension in the ARB. This stage is then compared with a new synthesis of the earliest Cretaceous contraction along the Andes. This analysis reveals that the ARB likely holds the oldest post-Gondwanic synorogenic unit along the orogen and more significantly, that Andean birth was a diachronous process which propagated northward since the late Early Cretaceous. The latter findings have major implications for the evolution of the Andes and shed light into the driving mechanism behind initial orogeny.

U-PB geochronology and magnetostratigraphy of a north Patagonian syn-orogenic Miocene succession: Tectono-stratigraphic implications for the foreland system configuration

The syn-orogenic Miocene deposits of the Patagonian Foreland System were the focus of numerous works in the latest years, due to their central role in the comprehension of the tectono-stratigraphy and tectonic evolution related to the Patagonian Andean growth. In this work we present a chronostratigraphic scheme based on magnetostratigraphy and UPb geochronology for one of the syn-orogenic successions of the Patagonian Foreland System: the Paso del Sapo Basin. The sequence is constrained to an age of >14.9 to <11.6 Ma, establishing ages of >14.9–14.6 Ma for the basal alluvial systems of La Pava Formation, with mean sedimentation rates of 4.2 cm/kyr; of 14.6 to 12.8–12.7 Ma for the lacustrine - deltaic environments of the lower Collón Cura Formation, with sedimentation rates ranging from 1.6 to 26.0 cm/kyr; and of 12.8–12.7 to <11.6 Ma for the alluvial systems of the upper Collón Cura Formation, with mean sedimentation rates of 8.5 cm/kyr. Our results indicate a continuous contractional tectonic phase at least during this time span (>14.9 to <11.6 Ma), which implicates that the Patagonian Foreland System at these latitudes was synchronously deformed with the tectonic activity along the Andean region.

The Topographic Evolution of the Central Andes

Changes in topography on Earth, particularly the growth of major mountain belts like the Central Andes, have a fundamental impact on regional and global atmospheric circulation patterns. These patterns, in turn, affect processes such as precipitation, erosion, and sedimentation. Over the last two decades, various geochemical, geomorphologic, and geologic approaches have helped identify when, where, and how quickly topography has risen in the past. The current spatio-temporal picture of Central Andean growth is now providing insight into which deep-Earth processes have left their imprint on the shape of the Earth's surface.

Revisiting the Crustal Structure and Kinematics of the Central Andes at 33.5°S: Implications for the Mechanics of Andean Mountain Building

AbstractThe Andean belt is the only present‐day active case example of a subduction‐type orogeny. However, an existing controversy opposes classical views of Andean growth as an east verging retro wedge, against a recently proposed bivergent model involving a primary west vergent crustal‐scale thrust synthetic to the subduction. We examine these diverging views by quantitatively reevaluating the orogen structural geometry and kinematics at the latitude of 33.5°S. We first provide a 3‐D geological map and build an updated section of the east vergent Aconcagua fold‐and‐thrust belt (Aconcagua FTB), which appears as a critical structural unit in this controversy. We combine these data with geological constraints on nearby structures to derive a complete and larger‐scale section of the Principal Cordillera (PC) within the fore‐arc region. We restore our section and integrate published chronological constraints to build an evolutionary model showing the evolving shortening of this fore‐arc part of the Andes. The proposed kinematics implies uplift of the Frontal Cordillera basement since ~20–25 Ma, supported by westward thrusting over a crustal ramp that transfers shortening further west across the PC. The Aconcagua FTB is evidenced as a secondary east verging roof thrust atop the large‐scale basement antiform culmination of the Frontal Cordillera. We estimate a shortening of ~27–42 km across the PC, of which only ~30% is absorbed by the Aconcagua FTB. Finally, we combine these findings with published geological data on the structure of the eastern back‐arc Andean mountain front and build a crustal‐scale cross section of the entire Andes at 33.5°S. We estimate a total orogenic shortening of ~31–55 km, mainly absorbed by crustal west vergent structures synthetic to the subduction. Our results provide quantitative key geological inferences to revisit this subduction‐type orogeny and compare it to collisional alpine‐type orogenic belts.

Andean growth and monsoon winds drive landscape evolution at SW margin of South America

In the Atacama Desert, the driest place on Earth located at the subduction margin of the Andes, the landscape evolves very slowly and changes in tectonic or erosion processes remain for a long time in the memory of topography. At latitude ∼19°30′S, a threshold between exoreic and endoreic drainage regimes is clearly associated with the latitudinal gradient imposed by the modern monsoon (carrying humidity from the Atlantic) and disposed obliquely over catchments draining the Andes to the Pacific. We summarize the geomorphic, geological and climatic data in the threshold area. We then use these data to constrain numerical experiments of drainage evolution. Data and experimental results are consistent with the development of a flat low-energy morphology, close to sea level, interrupted at ≤10 Ma by tectonic uplift prevailing to the present suggesting trench-ward relief growth by incorporation of the coastal Atacama region to the Andes mountain belt.

Response of meteoric δ18O to surface uplift — Implications for Cenozoic Andean Plateau growth

The timing and magnitude of surface uplift provide important constraints on geodynamic models of orogen formation. Oxygen isotope (δ18O) and mass-47 isotopolog (Δ47) compositions from terrestrial carbonate sediments have been used with modern isotope and temperature lapse rates to infer past surface elevations of the Andes. However, these paleoaltimetry interpretations are contentious because variations in the oxygen isotope composition in meteoric water (δ18Op) are caused by changes in elevation (orographic) and regional climate. Here, we use a limited-domain isotope-tracking general circulation model to simulate changes in δ18Op and isotopic lapse rates in response to Andean surface uplift, and to re-evaluate δ18O and Δ47 changes in late Miocene carbonates previously associated with rapid Andean growth. Results indicate that Andean surface uplift leads to changes in low-level atmospheric circulation and an increase in precipitation along the eastern Andean flank which influences isotopic source and amount effects. Simulated changes in Andean δ18Op are not systematic with an increase in surface elevation, but are instead a function of orographic thresholds that abruptly change regional climate. A δ18Op decrease of >5‰ over the central Andes and an increase in isotopic lapse rates (up to 0.8‰km−1) coincide with Andean surface uplift from 75 to 100% of modern elevation. These changes in the isotopic signature could account for the entire 3–4‰ δ18O depletion in late Miocene carbonate nodules, and suggest an Andean paleoelevation of ~3000m (75% of modern elevations) before 10Ma.

Andean growth and the deceleration of South American subduction: Time evolution of a coupled orogen-subduction system

Present-day orography at the Andean margin is a result of isostasy, tectonic accretion, and erosional processes. The resulting excess mass of the Andes gives rise to frictional stresses on the seismogenic plate interface that resist the sinking of the subducting slab into the upper mantle. Thus, subduction rates should be sensitive to the time-dependent dynamics of a back-arc orogen, as well as erosional or accretional processes that affect orogen growth. Here we develop a two-dimensional coupled orogen–slab model that allows for the prediction of orogen size and plate motion in response to both tectonic and erosional forcing. We find that the frictional force exerted by the orogen on the subducting slab grows quadratically with orogen width and that the frictional resistance typically balances 10–50% of the slab pull force. The time evolution of the coupled orogen-subduction zone system is largely controlled by the rate of orogen growth, which is controlled by the rate of convergence and the erosivity of the climate state. In the case of the Andean margin, our models show that Miocene aridification leads to reduced erosion, increased orogen growth, greater frictional resistance to subduction, and, ultimately, to a ~ 50% reduction in the convergence rate between the Nazca and South American plates.

High-level surfaces, plateau uplift, and foreland development, Bolivian central Andes

Research Article| August 01, 1993 High-level surfaces, plateau uplift, and foreland development, Bolivian central Andes T. L. Gubbels; T. L. Gubbels 1Department of Geological Sciences, Cornell University, Ithaca, New York 14853-1504 Search for other works by this author on: GSW Google Scholar B. L. Isacks; B. L. Isacks 1Department of Geological Sciences, Cornell University, Ithaca, New York 14853-1504 Search for other works by this author on: GSW Google Scholar E. Farrar E. Farrar 2Department of Geological Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada Search for other works by this author on: GSW Google Scholar Geology (1993) 21 (8): 695–698. https://doi.org/10.1130/0091-7613(1993)021<0695:HLSPUA>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation T. L. Gubbels, B. L. Isacks, E. Farrar; High-level surfaces, plateau uplift, and foreland development, Bolivian central Andes. Geology 1993;; 21 (8): 695–698. doi: https://doi.org/10.1130/0091-7613(1993)021<0695:HLSPUA>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Newly dated Tertiary strata in the Bolivian central Andean plateau and synthesis of the Tertiary record in the adjacent Subandean fold-thrust belt constrain the age of deformation in both regions. Age of deformation within the plateau is determined by dated crosscutting relations associated with a regionally extensive high-level surface known as the San Juan del Oro surface. New 40Ar-39Ar dates on undeformed strata above the high-level surface preclude significant upper-crustal shortening within the Eastern Cordillera after 10 Ma. Tertiary strata within the adjacent Subandean region demonstrate that formation of the fold-thrust belt occurred after 10 Ma. On the basis of these data, we propose a two-stage model of late Cenozoic Andean growth that links plateau uplift to the development of the fold-thrust belt. In the first stage, early plateau uplift occurred in response to widespread compressional deformation of the plateau (Eastern Cordillera and Altiplano). During the second stage, beginning after 10 Ma, upper-crustal deformation within the plateau terminated, and the Subandean fold-thrust belt developed. Crustal-scale eastward thrusting along the eastern margin of the Eastern Cordillera drove Subandean folding and thrusting; the Eastern Cordillera served as the "bulldozer" for the deforming Subandean wedge. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.